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Published: 4 June 2021
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1

Silva, Helen Rosa da. "Padrões espaciais e temporais na amplitude de nicho climático de vertebrados terrestres." Universidade Federal de Goiás, 2015. http://repositorio.bc.ufg.br/tede/handle/tede/5527.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Understanding how species are distributed across space and what determines where they live is one of the oldest goals in Ecology. The concept of niche is very closely related to this goal. In fact, environmental variables are frequently used to predict the potential distribution of species. Niche amplitude is an important concept which helps us to understand which part of the available environmental space each species occupies, and how much of their niches overlap. Here we used a measure of niche amplitude based on the minimum and maximum tolerances of terrestrial vertebrates (except reptiles) for each variable related to climate. We calculated a single measure of niche amplitude for each species by considering together all chosen environmental variables. We used this number to first investigate the presence of latitudinal gradient in niche amplitude across the study area, which comprised the whole terrestrial globe. There is a significant correlation between niche amplitude and latitude for Old World birds. Second we tried to identify some phylogenetic structure in niche amplitude for birds. For this goal, we calculated the pair-wise niche overlap, and then compared the degree of overlap with pair-wise phylogenetic distances. We found no relationship between niche overlap and phylogenetic distance. We conclude that the absence of phylogenetic signal in niche overlap is due to the high dispersion capability of birds in general. If species have a high geographic range, they consequently have high niche amplitude, and therefore high overlap rates. Finally, we found a clear tendency of positive local spatial autocorrelation in mean niche overlap, as neighbor cells tend to show similar rates of niche overlap between species.
Compreender os fatores que determinam a distribuição das espécies no espaço geográfico é uma das questões mais importantes em ecologia. O conceito de nicho é fortemente relacionado a essa questão. Não por acaso, variáveis ambientais são comumente usadas para inferir a distribuição potencial de espécies. Amplitude de nicho é uma medida importante que nos possibilita saber que proporção do espaço ambiental cada espécie ocupa. Assim, podemos também identificar que proporção do espaço ocupado por cada espécie, seu nicho, é sobreposta pelo nicho das espécies coexistentes. No presente trabalho utilizamos uma medida de amplitude de nicho específica baseada na soma das tolerâncias para cada variável climática utilizada. Utilizamos essa medida para investigar, primeiramente, a presença de estrutura espacial, especificamente gradiente latitudinal, na amplitude de nicho de vertebrados terrestres (exceto répteis), numa escala global. Apenas aves do Velho Mundo apresentaram amplitude de nicho negativamente associada à latitude. Posteriormente, investigamos a presença de estrutura filogenética na amplitude de nicho em Aves, baseados na hipótese de conservação de nicho. Para esse objetivo calculamos a sobreposição de nicho par-a-par e então correlacionamos essa medida com as distâncias filogenéticas. Não houve correlação entre proximidade filogenética e sobreposição de nicho. Tal resultado pode estar relacionado à grande capacidade de dispersão de aves. Se a área de ocupação geográfica é ampla, a amplitude das tolerâncias é em geral alta e consequentemente a sobreposição média entre diferentes espécies. Finalmente houve forte indício de autocorrelação espacial positiva na sobreposição média por célula entre células próximas, indicando que áreas próximas tendem a apresentar espécies com taxas semelhantes de sobreposição de nicho.
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2

Milne, Margaret Georgina. "Environmental niche evolution and ancestral niche reconstruction." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709832.

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Quantifying the diversity and distribution of the world’s biota in both space and time is a fundamental goal of modern biology, however ecologists also face the added pressure of understanding how species may respond to anthropogenically driven environmental changes. The relationship between species distributions and the environment can be captured in Environmental Niche Models (ENM’s), which create mathematical models linking species occurrences to ecological factors at a specific point in time. Whilst this approach is very useful, it can be improved by the incorporation of phylogenetic data (with estimated species divergence dates) to explore how the environmental niche has changed for a whole clade through evolutionary time. This thesis aims to explore whether niches are conserved over the life history for individual species, and for entire genera through evolutionary time. The research aims to firstly improve the current iteration of the Coleopteran Mutual Climatic Range (MCR) approach by automating the climate envelope creation process; secondly, to determine whether the expression of the realised climate niche has changed for four members of the Staphylinid Olophrum genus through the Quaternary and thirdly, to create a historical bio-geographical model indicating the likely mode of evolution between sister-taxa in the Dytiscidae Hydroporus genus. Lastly, the ancestral climatic niche of the Hydroporus genus is modelled in order to determine any patterns in climate niche evolution. This is achieved by bringing together phylogenetic data, occurrence data and environmental data under a Bayesian analysis framework to reconstruct the values for environmental niche traits at internal nodes in a phylogenetic tree.
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3

Lima, Alessandra Vallim [UNESP]. "Niche Modelling: a comparison between modelling methods best applied for Cnidaria niche dispersion studies." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/150823.

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Nas ultimas décadas, modelagem de nicho ecológico vem recebendo maior atenção em diversas áreas da biologia devido a evolução dos computadores pessoais e aumento dos dados disponíveis utilizados para a modelagem. Os resultados obtidos podem ser utilizados em ações preventivas, tais quais manejo de espécie e acompanhamento da distribuição de espécies invasoras. Desde o aumento dessa popularidade, diversos algoritmos estão disponíveis e testes estão em andamento para averiguar suas performances em relação a diferentes filos. Invertebrados marinhos, mais especificamente cnidários, apresentam poucos estudos nesse ramo, devendo receber mais atenção nos próximos anos devido ao aumento global das populações de aguas vivas (blooms), e branqueamento em quase todos os recifes de corais. Devido a essa lacuna em informação, este grupo foi escolhido para comparar três algoritmos. Utilizamos o MAXENT, GARP e AquaMaps em suas formas de desktop e os selecionamos baseado em outros estudos comparando algoritmos. Utilizamos diferentes organismos do filo cnidária, Lychnorhiza lucerna, Chrysaora lactea, Phyllorhiza punctata, Tamoya haplonema, Ceriantheomorphe brasiliensis e Mussismilia hispida, para comparar os algoritmos e averiguar qual demonstrou melhor performance. Nossos resultados mostram que o MAXENT superou os outros algoritmos tanto com relação a Área Sob a Curva ROC (AUC), quanto com relação aos mapas de distribuição. O GARP apresentou resultados variados com mapas generalizados e AquaMaps foi o menos confiável. Nossos resultados são similares aqueles encontrados em diversas publicações, significando então, que o MAXENT é o algoritmo mais confiável em se tratando da modelagem de nicho desses organismos.
Recently, ecological niche modelling has been receiving more attention in several areas in biology, due to the evolution of personal computers, and the increasing availability of data used in modelling. The results obtained can be used in preventive actions such as species management and invasive species distribution. Since its increasing popularity, several algorithms are available and undergoing tests regarding their performance towards different phylum. Marine invertebrates, more specifically cnidarians, present few studies on this field, and should receive closer attention in the next years due to worldwide increases in jellyfish population (blooms), and bleaching in almost every known shallow water coral reef. Because of this gap of information, we chose this still poor studied group to compare three algorithms. We used MAXENT, GARP and AquaMaps in its desktop form and selected them based on other studies comparing algorithms. Our aim was to, based on different organisms of the phylum Cnidaria, Lychnorhiza lucerna, Chrysaora lactea, Phyllorhiza punctata, Tamoya haplonema, Ceriantheomorphe brasiliensis and Mussismilia hispida, compare those algorithms and examine which one performed the best. Our results shown that MAXENT outperformed the other algorithms both regarding de Area Under the ROC Curve (AUC) and the map distribution. GARP show varying results with generalized maps and AquaMaps was the least accurate of them. Our results are similar to those found in other papers, thus meaning that MAXENT is the most reliable software when it comes to modelling these animals.
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4

McHugh, Sean W. "Phylogenetic Niche Modeling." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104893.

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Projecting environmental niche models through time is a common goal when studying species response to climatic change. Species distribution models (SDMs) are commonly used to estimate a species' niche from observed patterns of occurrence and environmental predictors. However, a species niche is also shaped by non-environmental factors--including biotic interactions and dispersal barrier—truncating SDM estimates. Though truncated SDMs may accurately predict present-day species niche, projections through time are often biased by environmental condition change. Modeling niche in a phylogenetic framework leverages a clade's shared evolutionary history to pull species estimates closer towards phylogenetic conserved values and farther away from species specific biases. We propose a new Bayesian model of phylogenetic niche implemented in R. Under our model, species SDM parameters are transformed into biologically interpretable continuous parameters of environmental niche optimum, breadth, and tolerance evolving under multivariate Brownian motion random walk. Through simulation analyses, we demonstrated model accuracy and precision that improved as phylogeny size increased. We also demonstrated our model on a clade of eastern United States Plethodontid salamanders by accurately estimating species niche, even when no occurrence data is present. Our model demonstrates a novel framework where niche changes can be studied forwards and backwards through time to understand ancestral ranges, patterns of environmental specialization, and niche in data deficient species.
Master of Science
As many species face increasing pressure in a changing climate, it is crucial to understand the set of environmental conditions that shape species' ranges--known as the environmental niche--to guide conservation and land management practices. Species distribution models (SDMs) are common tools that are used to model species' environmental niche. These models treat a species' probability of occurrence as a function of environmental conditions. SDM niche estimates can predict a species' range given climate data, paleoclimate, or projections of future climate change to estimate species range shifts from the past to the future. However, SDM estimates are often biased by non-environmental factors shaping a species' range including competitive divergence or dispersal barriers. Biased SDM estimates can result in range predictions that get worse as we extrapolate beyond the observed climatic conditions. One way to overcome these biases is by leveraging the shared evolutionary history amongst related species to "fill in the gaps". Species that are more closely phylogenetically related often have more similar or "conserved" environmental niches. By estimating environmental niche over all species in a clade jointly, we can leverage niche conservatism to produce more biologically realistic estimates of niche. However, currently a methodological gap exists between SDMs estimates and macroevolutionary models, prohibiting them from being estimated jointly. We propose a novel model of evolutionary niche called PhyNE (Phylogenetic Niche Evolution), where biologically realistic environmental niches are fit across a set of species with occurrence data, while simultaneously fitting and leveraging a model of evolution across a portion of the tree of life. We evaluated model accuracy, bias, and precision through simulation analyses. Accuracy and precision increased with larger phylogeny size and effectively estimated model parameters. We then applied PhyNE to Plethodontid salamanders from Eastern North America. This ecologically-important and diverse group of lungless salamanders require cold and wet conditions and have distributions that are strongly affected by climatic conditions. Species within the family vary greatly in distribution, with some species being wide ranging generalists, while others are hyper-endemics that inhabit specific mountains in the Southern Appalachians with restricted thermal and hydric conditions. We fit PhyNE to occurrence data for these species and their associated average annual precipitation and temperature data. We identified no correlations between species environmental preference and specialization. Pattern of preference and specialization varied among Plethodontid species groups, with more aquatic species possessing a broader environmental niche, likely due to the aquatic microclimate facilitating occurrence in a wider range of conditions. We demonstrated the effectiveness of PhyNE's evolutionarily-informed estimates of environmental niche, even when species' occurrence data is limited or even absent. PhyNE establishes a proof-of-concept framework for a new class of approaches for studying niche evolution, including improved methods for estimating niche for data-deficient species, historical reconstructions, future predictions under climate change, and evaluation of niche evolutionary processes across the tree of life. Our approach establishes a framework for leveraging the rapidly growing availability of biodiversity data and molecular phylogenies to make robust eco-evolutionary predictions and assessments of species' niche and distributions in a rapidly changing world.
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5

Gurgel, Priscila Cabral Silveira. "Reproductive modes are associated to climatic niche evolution in treefrogs (anura: hylidae)." Universidade Federal de Goiás, 2016. http://repositorio.bc.ufg.br/tede/handle/tede/6263.

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Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The similarity of life-history traits among closely related species is a well-known pattern in evolutionary biology. Thus, closely related species tend to be more akin to each other than to distantly related ones. The propensity of closely related species to conserve climatic niche features over macroevolutionary time can be defined as climatic niche conservatism. Recent studies have shown the importance of environmental variables with regards to the diversity and distribution of anurans with differences in their reproductive traits under an evolutionary perspective. In this work, using frog species in the Hylidae family, we tested the hypothesis that species more independent from main bodies of water for reproduction are restricted to areas with higher temperature and precipitation means. We also investigated the evolution of climatic niche features of species with different degrees of dependence on water for reproduction. Our results corroborate the first hypothesis and show that terrestrial egg-laying species, in the Hylinae subfamily, have more conserved climatic niche position when compared to Hylinae species that deposits their eggs and tadpoles in main water bodies. Thus, we suggest that reproductive modes are associated with variation in the evolution of climatic niches of frogs.
A similaridade entre atributos de espécies aparentadas é um padrão tradicional reconhecido em biologia evolutiva. Espécies aparentadas tendem ser mais similares entre si do que com espécies não aparentadas. A tendência de espécies aparentadas conservar as características de seu nicho ao longo do tempo macroevolutivo pode ser definido como conservação filogenética de nicho. Estudos recentes tem mostrado a importância das variáveis climáticas na distribuição de anfíbios anuros com diferentes modos reprodutivos utilizando uma abordagem evolutiva. Neste trabalho, usando as espécies de pererecas da família Hylidae, testamos a hipótese de que espécies menos dependentes dos corpos d'água para reprodução ocorrem em áreas mais quentes e mais úmidas. Além disso, investigamos como foi a evolução dos atributos do nicho climático (posição e amplitude) de espécies, da subfamília Hylinae, com diferentes níveis de dependência dos corpos d'água para reprodução. Nossos resultados corroboram a primeira hipótese e mostram que, espécies da subfamília Hylinae que depositam seus ovos fora da água estão restritas a lugares mais quentes e mais úmidos. Além disso, tais espécies tem o nicho climático mais conservado do que espécies que depositam tanto ovos como girinos em corpos d'água principais. Portanto, sugerimos que os diferentes modos reprodutivos refletem em diferenças na evolução do nicho climático nas espécies da subfamília Hylinae.
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6

Fernandes, Ubirajara Lima. "Ecologia trÃfica de quatro espÃcies de peixes de um rio no semiÃrido, Pentecoste - CearÃ." Universidade Federal do CearÃ, 2011. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=7965.

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A maioria dos rios do semiÃrido apresentam regimes irregulares e intermitentes, com um sà perÃodo anual de escoamento na chegada das precipitaÃÃes pluviomÃtricas que caracterizam o perÃodo chuvoso. Nesses rios, as perturbaÃÃes hidrolÃgicas naturais exercem forte influÃncia na organizaÃÃo do sistema, sendo as interaÃÃes alimentares complexas e modificadas pela sazonalidade e pela produtividade do sistema. A dieta de peixes pode variar de acordo com a disponibilidade de recursos alimentares de origem autÃctone ou alÃctone, bem como em resposta à variaÃÃo sazonal. A hipÃtese do presente estudo à de que em um rio do semiÃrido as espÃcies de peixes herbÃvoras/ onÃvoras apresentam partilha de recursos trÃficos. O objetivo foi determinar a partilha de recursos trÃficos a partir da dieta de quatro espÃcies de peixes no rio Curu. As coletas foram realizadas em um trecho do rio Curu (Pentecoste, CearÃ), no perÃodo chuvoso de 2010. Foi analisado o conteÃdo estomacal de 197 indivÃduos das seguintes espÃcies: Astyanax bimaculatus (27), Astyanax fasciatus (79), Poecilia vivipara (90) e Hypostomus jaguribensis (1), pelo mÃtodo volumÃtrico e frequÃncia de ocorrÃncia, para o cÃlculo do Ãndice alimentar (IAi). Com os dados morfomÃtricos foi obtido o Quociente Intestinal (QI). A amplitude de nicho foi estimada atravÃs do Ãndice de Levins e a sobreposiÃÃo trÃfica atravÃs do Ãndice de Pianka. PadrÃes de sobreposiÃÃo de nicho trÃfico foram calculados e estatisticamente testados contra um modelo nulo, atravÃs dos algoritmos de randomizaÃÃo RA3 e RA4. A dieta de A. bimaculatus foi constituÃda por 13 itens, e a de A. fasciatus constituÃda por 15, com preferÃncia alimentar pela alga filamentosa Spirogyra em ambas as espÃcies, sendo a importÃncia alimentar de 89,34% para A. bimaculatus e 96,86% A. fasciatus. A dieta de P. vivipara foi constituÃda por 60 itens, com maior importÃncia para as algas diatomÃceas (28,82%), clorofÃceas (23,17%) e cianofÃceas (5,2%), tendo as clorofÃceas Spirogyra e Closterium, maior importÃncia alimentar com 12,89% e 8,85%, respectivamente e fragmentos de insetos aquÃticos com 39,18%. A dieta de H. jaguribensis esteve constituÃda por 42 itens alimentares, com maior importÃncia para Spirogyra com 23,42%, e Compsopogon com 19%. O grupo diatomÃcea apresentou maior nÃmero de itens na dieta com 21 tÃxons e 16,38% de IAi, seguido pelo item alimentar detrito com 27,72% de importÃncia. De acordo com o quociente intestinal A. bimaculatus e A. fasciatus apresentam intestino caracterÃstico de carnÃvoro/onÃvoro e P. vivipara de herbÃvoro. A anÃlise de variÃncia (ANOVA) para os valores mÃdios do quociente intestinal dos peixes analisados foi significativa com F= 3,50, df = 2, p< 0,05. A largura de nicho foi maior em P. vivipara com 1.32, seguido por A. bimaculatus com 0,78 e A. fasciatus com 0,426. Maior sobreposiÃÃo de nicho ocorreu entre as espÃcies de Astyanax com o valor de 0,98. A anÃlise dos modelos nulos realizados pelos itens totais e os itens agrupados indicou que os valores observados foram sempre maiores do que os esperados para a matriz RA3 e RA4. A variÃncia mÃdia observada tambÃm foi maior do que a simulada. De acordo com a dieta das quatro espÃcies analisadas, destacam a importÃncia de itens de origem autÃctone, principalmente as algas. Os modelos nulos indicam que as espÃcies de peixes herbÃvoras/onÃvoras apresentam partilha de recursos trÃficos, ou seja, a competiÃÃo nÃo à o agente estruturador dessa comunidade.
The semiarid rivers present two patterns: the intermittent and the irregular one, with a single flowing off period per year, during the rainy season. In these rivers, the natural hydrological disturb acts as an important factor driving the organization of the system, in which feeding interactions are complex and modified by seasonality and system productiveness. Fishes often feed on autochthonous or allochthonous resources, with their diets varying according to the with seasonal variation of food availability. The hypothesis of this the present study is that in the semiarid river herbivorous/onivorous fish species present trophic resources partitioning. The major aim of this study the present investigation is was to determine the trophic resources partitioning for four species of fishes at in the Curu River. Field work collections were carried out throughout the rainy season, at the Curu River, in Pentecoste city town, in Cearà state. The stomach content of 197 individuals of the species Astyanax bimaculatus (27), Astyanax fasciatus (79), Poecilia vivipara (90) e Hypostomus jaguribensis (1) was analyzed through the volumetric method in order to obtain for the frequency of each feeding item, so that the Index of Alimentary Importance (IAi) could have been measured. The morphometric data were used to obtain the intestinal quotient (IQ), the niche breadth estimated for the Levinsâ index and the trophic overlap for the Piankaâs index. Patterns of trophic niche overlap were calculated and statistically tested against a null model using the randomization algorithms RA3 and RA4. A. bimaculatus and A. fasciatus fed on 13 and 15 items, respectively. Both species presented feeding preferences for the filamentous algae Spirogyra sp., encompassing 89.34% and 96.86% of their diets, respectively. Poecilia viviparaâs diet comprised 60 items, mainly made up of algae (Bacillariophyta - 28.82%, Chlorophyta - 23.17% and Cyanophyta â 5.2%). Amongst the âgreen algaeâ, Spirogyra sp. (12.89%) and the Closterium sp. (8.85%) were the chief principal items eaten. Aquatic insects (39.18%) made up the second most important item. A total of 42 items compounded the diet of H. jaguribensis, which detritus (27,72%), the algae Spyrogira sp. (23.42%) and Compsopogon sp. (19%) were the foremost most important items. The diatom group comprised the most abundant item, with 21 taxa and 16.38% of IAi. According to the intestinal quotient, A. bimaculatus e A. fasciatus showed a typical carnivorous/omnivorous intestine, whereas P. vivipara showed a herbivorous one. The analysis of variance shows that the intestinal quotient varied among species (F = 3.50; d.f = 2; p < 0.05). The niche breadth was greater for P. vivipara (1.32), followed by A. bimaculatus (0.78) and A. fasciatus (0.426). The higher niche overlap occurred within the Astyanax species (0.98). The null model analysis carried out for the total and clustered grouped items indicated that the observed values were always higher than the expected ones for the RA3 and RA4 matrices. In addition, the mean observed variance was higher than the simulated one. The four studied fish species fed mainly on autochthonous items, chiefly on algae. The null models demonstrated that there is a resource partitioning amongst these herbivorous/omnivorous fish species, where competition seems not to be the structuring agent.
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7

Messias, Patrícia. "Delimitação de espécies do complexo Aspidosperma pyrifolium Mart. & Zucc. (Apocynaceae)." Botucatu, 2019. http://hdl.handle.net/11449/182518.

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Orientador: Ingrid Koch
Resumo: Aspidosperma pyrifolium Mart. & Zucc. é uma espécie com distribuição ampla e disjunta, variação morfológica e taxonomia complexa. Neste estudo é tratada como um complexo de espécies, e utilizada como modelo para delimitação de espécies através de múltiplos critérios operacionais (genéticos, morfológicos e ecológicos). Consideramos que espécies são segmentos de linhagens de uma metapopulação evoluindo separadamente, pois este é um conceito universal que diminuiu as visões conflitantes do que é considerado espécie. Realizamos análises filogenéticas com dados concatenados (ITS e rpl32-trnL) e de coalescência para testar o monofiletismo do complexo e seus grupos. Desenvolvemos marcadores microssatélites polimórficos para A. pyrifolium usados na avaliação da diversidade genética e estruturação de cinco populações naturais. Analisamos a morfologia através de morfometria, incluindo características quantitativas, tanto vegetativas quanto reprodutivas. As análises ecológicas, incluíram modelagem e testes de similaridade de nicho ecológico. Nossos resultados recuperaram o complexo A. pyrifolium como monofilético, com 3 subclados relacionados a regiões geográficas e vegetações específicas, resultados também corroborados na árvore de espécies. O clado 1 ocorre na Caatinga no Nordeste do Brasil, o clado 2 nas manchas de Floresta Estacional na região Centro-Oeste no Brasil e clado 3 na vegetação chaqueana no Mato grosso do Sul, Paraguai e Bolívia. Todas as análises de estrutura populaciona... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Aspidosperma pyrifolium Mart. & Zucc. is a species with wide distribution and disjunct, morphological variation and complex taxonomy. In this study, we treated it as a species complex, and used as a model for species delimitation using multiple operational criteria (genetic, morphological and ecological). We consider species as segments of separately evolving metapopulation lineages, since this is a universal concept that diminished the conflicting visions of what is considered species. For this, we performed phylogenetic with concatenated data (ITS and rpl32-trnL) and coalescence analyzes to test the monophyly of the complex and its groups. We developed polymorphic microsatellites for complex A. pyrifolium for evaluated the genetic diversity and structure of five natural population. We analyzed morphology through morphometry, including quantitative characteristics, both vegetative and reproductive. The ecological analyzes included modeling and testing of ecological niche similarity. Our results recovered Aspidosperma pyrifolium complex as monophyletic, with 3 subclades related to geographic regions and specific vegetation, results also corroborated in the species tree. Clade 1 occurs in the Caatinga in Northeast Brazil, clade 2 in the Seasonal Forest patches in the Center-West region of Brazil and clade 3 in the Chaqueana vegetation in Mato Grosso do Sul, Paraguay and Bolivia. All analyzes of population structure suggested the formation of two genetic groups, one with the po... (Complete abstract click electronic access below)
Doutor
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8

Moonlight, Peter Watson. "Linking speciation and the niche : taxonomy, phylogeny and niche evolution in neotropical Begonia." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8397/.

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Begonia L. is one of the ten largest plant genera with >1,830 currently accepted species distributed throughout the tropical Americas, Africa and Asia. This exceptional diversity offers the opportunity to study the processes underlying recent and rapid radiations, including the theory of adaptive radiations, but also poses major challenges. Methods to test adaptive radiation theory require sufficient occurrence data to produce species distribution models for the majority of species in a group. In many groups, including Andean, Central American and Mexican Begonia, this criterion is not met. The availability of specimen data on GBIF for species distribution modelling in vascular plants as a whole was assessed. The potential contribution of databased and freely available but indetermined or non-georeferenced specimens to the field of species distribution modelling was estimated. More than half of vascular plant species are currently unavailable for species distribution modelling. Our results indicate 22% of currently unavailable species could be modelled with already available herbarium data that is not yet georeferenced or determined to species. We argue that a greater focus on georeferencing and identification skills are vital if herbaria are to contribute fully to the growing field of species distribution modelling. We highlight those families and geographic regions that would most benefit from this approach and discuss the historical factors have influenced differences among regions. Another prerequisite for species distribution modelling is a stable species level taxonomy. In preparation for investigation involving SDM’s in Begonia, five taxonomic papers are presented, including revised species concepts, distribution data suitable for use in species distribution models, seven new species and a new section of Begonia. Three plastid markers for 574 species and 809 accessions of Begonia were used to produce the largest, most representative phylogeny of Begonia published to date. An updated sectional classification of the genus is provided. The sections of Begonia are used frequently as analogues to genera in other families but, despite their taxonomic utility, few of the current sections have been examined in the light of molecular phylogenetic analyses. The relationships among some species and sections are poorly resolved, but many sections and deeper nodes receive strong support. We recognise 77 sections of Begonia including four new sections: Astrotricha, Jackia, Kollmannia, and Stellanthera; five sections are reinstated from synonymy: Australes, Exalabegonia, Latistigma, Pereira and Poecilia; and four sections are newly synonymised. The new sectional classification is discussed with reference to identifying characters and previous classifications. Central to the theory of an adaptive radiation is that the majority of speciation events are adaptive, implying speciation driven by adaptation to different environments and resulting in niche shifts. Species in an adaptive radiation should display distinct ecological niches and environmental disparity across the group’s phylogeny should best fit a kappa ‘niche-shift’ or ‘speciational’ model of character evolution. These characteristics were tested in two clades of Neotropical Begonia. Species were compared through the comparison of their distributions in environmental space calculated from species distribution models. The fit of four models of environmental evolution (a kappa ‘niche-shift’ model, a Brownian motion model, an early-burst model, and a white noise model) to the observed niche disparity in the group were assessed using the Akaike Information Criterion Patterns of ecological diversification in the two clades of Begonia examined strongly diverge from those predicted by an adaptive model, and we conclude Begonia is not an adaptive radiation with respects to climatic niche. Ecological disparity within Begonia clades best fits the predictions of a Brownian model of niche evolution. The characteristics of a Brownian model include constant niche evolution over the phylogeny, no increases in niche evolution during speciation, and independent niche evolution in sister lineages. This is incompatible with the predictions of an adaptive radiation. We suggest the remarkable diversity of the genus has developed through geographic speciation, and subsequent adaptation to local environments. This phenomenon may be widespread among plant radiations in topographically- and environmentally-heterogeneous areas, and a re-evaluation of putative adaptive radiations throughout the world’s montane regions may be necessary.
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9

Lima, Alessandra Vallim. "Niche Modelling : a comparison between modelling methods best applied for Cnidaria niche dispersion studies /." São Vicente, 2017. http://hdl.handle.net/11449/150823.

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Orientador: Sérgio Nascimento Stampar
Abstract: Recently, ecological niche modelling has been receiving more attention in several areas in biology, due to the evolution of personal computers, and the increasing availability of data used in modelling. The results obtained can be used in preventive actions such as species management and invasive species distribution. Since its increasing popularity, several algorithms are available and undergoing tests regarding their performance towards different phylum. Marine invertebrates, more specifically cnidarians, present few studies on this field, and should receive closer attention in the next years due to worldwide increases in jellyfish population (blooms), and bleaching in almost every known shallow water coral reef. Because of this gap of information, we chose this still poor studied group to compare three algorithms. We used MAXENT, GARP and AquaMaps in its desktop form and selected them based on other studies comparing algorithms. Our aim was to, based on different organisms of the phylum Cnidaria, Lychnorhiza lucerna, Chrysaora lactea, Phyllorhiza punctata, Tamoya haplonema, Ceriantheomorphe brasiliensis and Mussismilia hispida, compare those algorithms and examine which one performed the best. Our results shown that MAXENT outperformed the other algorithms both regarding de Area Under the ROC Curve (AUC) and the map distribution. GARP show varying results with generalized maps and AquaMaps was the least accurate of them. Our results are similar to those found in other pape... (Complete abstract click electronic access below)
Resumo: Nas ultimas décadas, modelagem de nicho ecológico vem recebendo maior atenção em diversas áreas da biologia devido a evolução dos computadores pessoais e aumento dos dados disponíveis utilizados para a modelagem. Os resultados obtidos podem ser utilizados em ações preventivas, tais quais manejo de espécie e acompanhamento da distribuição de espécies invasoras. Desde o aumento dessa popularidade, diversos algoritmos estão disponíveis e testes estão em andamento para averiguar suas performances em relação a diferentes filos. Invertebrados marinhos, mais especificamente cnidários, apresentam poucos estudos nesse ramo, devendo receber mais atenção nos próximos anos devido ao aumento global das populações de aguas vivas (blooms), e branqueamento em quase todos os recifes de corais. Devido a essa lacuna em informação, este grupo foi escolhido para comparar três algoritmos. Utilizamos o MAXENT, GARP e AquaMaps em suas formas de desktop e os selecionamos baseado em outros estudos comparando algoritmos. Utilizamos diferentes organismos do filo cnidária, Lychnorhiza lucerna, Chrysaora lactea, Phyllorhiza punctata, Tamoya haplonema, Ceriantheomorphe brasiliensis e Mussismilia hispida, para comparar os algoritmos e averiguar qual demonstrou melhor performance. Nossos resultados mostram que o MAXENT superou os outros algoritmos tanto com relação a Área Sob a Curva ROC (AUC), quanto com relação aos mapas de distribuição. O GARP apresentou resultados variados com mapas generalizados e AquaM... (Resumo completo, clicar acesso eletrônico abaixo)
Mestre
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10

Russell, Vanessa. "Identifying Environmental Factors Driving Differences in Climatic Niche Overlap in Peromyscus Mice." Miami University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=miami1565722438217428.

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11

Pinto, Pedro Jorge Fernandes. "Factors that lead physicians to initiate and maintain relationships with credit unions: a case study - Unicred Fortaleza." Universidade Federal do CearÃ, 2007. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=3608.

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nÃo hÃ
The high inflationary indices that had lasted in Brazil in the 80âs, had been damaging, for several segments of the society, benefiting few economic sectors. Among those segments that had grown in this uncommon conjuncture, the financial institutions are distinguished, companies that focused their activities in terms of keeping public founds and application from federal governmentâs papers, avoiding to carry through operations of loans and financings, preventing to run in risk. The management used to maximize profits and to prevent risks took these institutions to carry through great investments in technological solutions and the main goal was to transform the processes of finance transferences into a very quick way and reduce the costs with salaries. As a consequence of this process the contact with clients became very impersonal. The view of knowing and evaluating the customers started right after the implantation of the Brazilian Real Plan was initiated after and beginning of the process of reduction of the inflation indices and taxes of interests. In this environment appeared the union corporations that work among doctors and belong to Unicred System, institutions that in last fifteen years comes conquering spaces in niches, that previously were exclusive for banks in commercial field and that encloses 129 cooperatives in Brazil. This paper presents an study about Unicred of Fortaleza, involving its controllers e cooperated clients, beyond the controllers of the Unicred Porto Alegre, Unicred of Southwestern Goias, Unicred of Southern Rio de Janeiro, Unicred Middle Plateaus and Unicred Saint Carlos, what are the only ones in Unicredâs System that work exclusively in the niche of doctors and their relatives. The work identify, in the perspective of the involved companies: the reasons from what doctors decided to belong to Unicred and maintain financial relationship with it, although all sort of financial institutions that can be found in the market; the view that they have of the services provided by their business; the importance of the main tools of marketing relationship used to conquer and maintain the associated partners and focus the risks of the competition of the banks over the niches in what the Unicred system what on. The study contributes in terms of making a review of the concept that doctors, in function of the image of a joined and cooperative class, have a strong cooperative feeling, being this the main booster of the growth of Unicred System.
Os elevados Ãndices inflacionÃrios que perduraram no Brasil na dÃcada de 1980, foram malÃficos para diversos segmentos da sociedade, beneficiando poucos setores econÃmicos. Entre os segmentos que cresceram nessa conjuntura incomum, destacam-se as instituiÃÃes financeiras, que focaram suas atividades na captaÃÃo de recursos junto ao pÃblico e aplicaÃÃo em tÃtulos do Governo Federal, evitando realizar operaÃÃes de emprÃstimos e financiamento para nÃo correrem riscos. As polÃticas de maximizar ganhos na captaÃÃo de recursos e evitar riscos nas operaÃÃes de crÃdito levaram essas instituiÃÃes a realizar elevados investimentos em soluÃÃes tecnolÃgicas, com o objetivo de tornar Ãgeis as transferÃncias de recursos, reduÃÃo dos custos operacionais e de mÃo-de-obra. Como conseqÃÃncia, o contato com a clientela tornou-se impessoal. A visÃo de obter resultados por meio do conhecimento e valorizaÃÃo do cliente iniciou-se apÃs a implantaÃÃo do Plano Real e da reduÃÃo dos Ãndices de inflaÃÃo e taxas de juros, que forÃaram os bancos a buscar novos ganhos na intermediaÃÃo financeira. Neste clima conturbado, surgiram as cooperativas de crÃdito, que atuam no segmento mÃdico associadas ao Sistema Unicred, instituiÃÃes que, nos Ãltimos quinze anos, conquistaram espaÃos em nichos anteriormente exclusivos dos bancos comerciais e que atualmente abrange 129 cooperativas em todo o Brasil. Esta dissertaÃÃo apresenta estudo realizado junto à Unicred Fortaleza, envolvendo seus cooperados e dirigentes, alÃm dos dirigentes da Unicred Porto Alegre, Sudoeste Goiano, Sul Fluminense, Planalto MÃdio e Unicred SÃo Carlos, que, a exemplo de Fortaleza, sÃo atualmente as cooperativas integrantes do Sistema Unicred a atuar, exclusivamente, com o nicho que abrange os profissionais mÃdicos e seus componentes familiares. O estudo identifica na perspectiva dos envolvidos: os motivos que levam os profissionais mÃdicos a se tornarem cooperados e a manterem relacionamento financeiro com a Unicred Fortaleza, apesar da diversidade de opÃÃes de instituiÃÃes financeiras existentes no mercado; a visÃo dos cooperados e dirigentes sobre os serviÃos ofertados por suas cooperativas; as principais ferramentas do marketing de relacionamento utilizadas na conquista e manutenÃÃo de cooperados; e destaca a ameaÃa da concorrÃncia dos bancos sobre o nicho de mercado atendido pelas cooperativas integrantes do Sistema Unicred. O estudo contribui para revisÃo do conceito de que os mÃdicos, em funÃÃo da imagem de classe unida e corporativista, teriam um forte sentimento cooperativista, sendo este o principal impulsionador do crescimento do Sistema Unicred.
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12

TABOSA, Lorena de Oliveira. "Aspectos da biologia reprodutiva e coexist?ncia temporal de duas esp?cies simp?tricas do g?nero Anoura, em Valen?a, Rio de Janeiro." Universidade Federal Rural do Rio de Janeiro, 2016. https://tede.ufrrj.br/jspui/handle/jspui/1554.

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Studies on reproductive patterns, temporal and seasonal activity and use of space by animals can contribute to the knowledge about the coexistence of similar morphologically and phylogenetically related species in a particular region. The aims of this study wasanalyze the reproductive biology and coexistence of two nectarivorous species, Anoura caudifer and A. geoffroyi, on Santu?rio de Vida Silvestre da Serra da Conc?rdia in Valenca, RJ. Samplings were conducted from Novembrer 2010 to February 2015, near a cave in which the species sheltered and in nearby trails. Anoura caudifer presented reproductive restricted monoestrous seasonal pattern, with pregnant in higher rainfall and temperature months of. The frequency of pregnant, lactating were not uniform, with peaks in a few months. The sex ratio was 0.5 female to 1 male. Anoura geoffroyi presented pattern reproductive poli?strico bimodal, with evident peak in the rainy months and possible second peak in the middle of the year, probably becausefemales migrated to another refuge. Frequencies of pregnant and lactating have not been uniform. The sex ratio was 1.6 to 1 female male. Although active males of both species were found in all months of the year, were porssible observe a pattern in response to female reproductive pattern. Differences in male and female physiology in response to high or low food availability may be the reason why only females are influenced by the increase in annual rainfall. Anoura caudifer and A. geoffroyi showed similar patterns in activity time, with peaks in the first two hours of the night, characteristic for nectarivorous and frugivorous bats. The frequency of A. caudifer capture proved to be similar in the cave trail and in other sampling sites, regardless of the presence of A. geoffroyi, which occurred almost entirely, on the trail of the cave. Probably this species employ different strategies to minimize a possible competition, as the differentiation in use of space in the Santu?rio da Conc?rdia.
Estudos sobre os padr?es reprodutivos, temporais e sazonais da atividade de animais, assim como o uso do espa?o, podem contribuir para o conhecimento sobre a coexist?ncia de esp?cies morfologicamente semelhantes e filogeneticamente relacionadas em uma determinada regi?o. Este trabalho teve objetivo de analisar aspectos da biologia reprodutiva e da coexist?ncia de duas esp?cies nectar?voras, Anoura caudifer e A. geoffroyi, no Santu?rio de Vida Silvestre da Serra da Conc?rdia, em Valen?a, RJ. Foram realizadas amostragens de novembro de 2010 a fevereiro de 2015, pr?ximo a uma gruta na quais essas esp?cies se abrigavam e em trilhas existentes no local. Anoura caudifer apresentou padr?o reprodutivo mono?strico sazonal restrito, com ocorr?ncia de gr?vidas nos meses de maior pluviosidade e temperatura. A frequ?ncia de gr?vidas, lactantes n?o foi uniforme, havendo picos em dois meses. A propor??o sexual foi de 0,5 f?mea para 1 macho. Anoura geoffroyi apresentou padr?o reprodutivo poli?strico bimodal, com pico evidente nos meses chuvosos e segundo poss?vel pico no meio do ano, pelo fato das f?meas migrarem para outro ref?gio. As frequ?ncias de gr?vidas e lactantes n?o foram uniformes. A propor??o sexual foi de 1,6 f?mea para 1 macho. Apesar de serem encontrados machos ativos sexualmente, de ambas as esp?cies, em todos os meses do ano, pode-se observar um padr?o em resposta ao padr?o reprodutivo das f?meas. Diferen?as na fisiologia de machos e f?meas em resposta ? alta ou baixa disponibilidade de alimento pode ser motivo pelo qual somente as f?meas s?o influenciadas pelo aumento da pluviosidade anual. Anoura caudifer e A. geoffroyi apresentaram padr?es de atividade hor?ria semelhantes, com picos nas duas primeiras horas da noite, caracter?sticos de morcegos nectar?voros e frug?voros. A frequ?ncia de captura de A. caudifer mostrou-se similar na trilha da gruta e nos demais locais amostrados, independente da presen?a de A. geoffroyi, que ocorreu quase em sua totalidade, na trilha da gruta. Provavelmente as esp?cies empregam diferentes estrat?gias para minimizar uma poss?vel competi??o tr?fica, como a diferencia??o no uso do espa?o no Santu?rio da Conc?rdia.
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13

Page, Brad, and page bradley@saugov sa gov au. "Niche partitioning among fur seals." La Trobe University. Zoology Department, School of Life Sciences, 2005. http://www.lib.latrobe.edu.au./thesis/public/adt-LTU20060622.153716.

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At Cape Gantheaume, Kangaroo Island (South Australia), adult male, lactating female and juvenile New Zealand (NZ) and Australian fur seals regularly return to the same colony, creating the potential for intra- and inter-specific foraging competition in nearby waters. I hypothesised that these demographic groups would exhibit distinct foraging strategies, which reduce competition and facilitate their coexistence. I analysed the diet of adult male, adult female and juvenile NZ fur seals and adult male Australian fur seals and studied the diving behaviour of adult male and lactating female NZ fur seals and the at-sea movements of juvenile, adult male and lactating female NZ fur seals. Female diet reflected that of a generalist predator, influenced by prey availability and their dependant pups� fasting abilities. In contrast, adult male NZ and Australian fur seals used larger and more energy-rich prey, most likely because they could more efficiently access and handle such prey. Juvenile fur seals primarily utilised small lantern fish, which occur south of the shelf break, in pelagic waters. Juveniles undertook the longest foraging trips and adult males conducted more lengthy trips than lactating females, which perform relatively brief trips in order to regularly nurse their pups. Unlike lactating females, some adult males appeared to rest underwater by performing dives that were characterised by a period of passive drifting through the water column. The large body sizes of adult males and lactating females facilitated the use of both benthic and pelagic habitats, but adult males dived deeper and for longer than lactating females, facilitating vertical separation of their foraging habitats. Spatial overlap in foraging habitats among the age/sex groups was minimal, because lactating females typically utilised continental shelf waters and males used deeper water over the shelf break, beyond female foraging grounds. Furthermore, juveniles used pelagic waters, up to 1000 km south of the regions used by lactating females and adult males. The age and sex groups in this study employed dramatically different strategies to maximise their survival and reproductive success. Their prey and foraging habitats are likely to be shaped by body size differences, which determine their different physiological constraints and metabolic requirements. I suggest that these physiological constraints and the lactation constraints on females are the primary factors that reduce competition, thereby facilitating niche partitioning.
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Page, Brad. "Niche partitioning among fur seals /." Access full text, 2005. http://www.lib.latrobe.edu.au/thesis/public/adt-LTU20060622.153716/index.html.

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Thesis (Ph.D.) -- La Trobe University, 2005.
Submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy to the Zoology Dept., School of Life Sciences, Faculty of Science, Technology and Engineering. Research. Includes bibliographical references (leaves 133-152). Also available via the World Wide Web.
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15

Reed, Daniel Thomas. "The evolution of niche width." Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3331.

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This thesis examines the ultimate and proximate determinants of niche width, with a focus on how cognition and biological information processing may drive the evolution of niche width. Using both field and laboratory experiments I investigate how learning can alter resource use in syrphids. Modelling biological information processing using artificial neural networks I consider how various ecological factors interact and can impact information processing to determine decision accuracy (a proposed factor in the evolution of niche width). Finally the ability of artificial neural networks to overcome evolutionary dead ends due to specialisation and functional loss is examined. I found that syrphids were able to use external, inter-specific cues to alter their resource use. Specialist artificial neural networks decision accuracy was altered by the introduction of the ecological variables they were subjected to and the loss of functionality can create an evolutionary dead end scenario only in very extreme cases or under specific ecological pressures. I studied the syrphid (Episyrphus balteatus) both in the field and under laboratory conditions. There is a huge amount of literature describing how bees use scent marks to aid decision making before landing on flowers but there is currently no work on the syrphids ability to detect and utilise these scent marks. The question I posed was ‘Can syrphids modify their pattern of resource utilisation by using this scent mark information?’ The field work was carried out using motion detection cameras positioned above flowers of knapweed (Centaurea nigra). The flowers had two different treatments: one was bagged overnight to prevent pollinator access and the other was left unbagged allowing foraging insects to deplete the nectar and pollen. Visits from both conditions were recorded and compared. I found that previously bagged flowers received more visits from both bumblebees (Bombus spp.) and syrphids suggesting that syrphids could also detect when a flower was depleted without landing. iii The laboratory tests were conducted in an arena using artificial flowers. The experiment was split into a learning phase and a testing phase. I tested the syrphids ability to recognise and learn an association to two different compounds, bee scent marks or 1-Hexanol. I found that syrphids could learn to associate both bee scent marks and 1-Hexanol with negative rewards and use this information to change their foraging behaviour. I used artificial neural networks to investigate differences between the decision accuracy of specialists and generalists when foraging under ecological pressures. Previous work has shown that specialists had higher decision accuracy when non-host selection carried a mild reward and I was interested to see how ecological variables would impact this advantage. The ecological conditions I considered were search costs, resource availability and starvation. To do this I trained neural networks to recognise different numbers of binary images (hosts) over a range of positive and negative non-host rewards or punishments. The fewer hosts a network had the more specialised it was. I found that both starvation and resource availability reduced the range of non-host values across which specialist networks had a fitness advantage over generalists. Interestingly I found that introducing search costs shifts the range of non-host values where specialist advantage occurs rather than narrowing them as in the previous conditions. Specialists suffering from search costs performed better when non-host selection carried a high to intermediate punishment. Finally, I used artificial neural networks to investigate the evolutionary dead end theory. This theory states that specialist organisms will lose genetic variation and will be unable to respond as effectively to ecological change. I first trained networks as specialists. These networks were then re-trained as generalists. While re-training networks had a percentage of their weights fixed to simulate the suggested reduction in evolutionary potential of specialists. Ecological conditions in these simulations were either non-host penalties, search costs or a combination of the two. I found that networks were relatively robust to loss of evolutionary iv potential. All of the networks performed well even at intermediate (50%) weight fixation. The application of search costs reduced overall network fitness but this effect was not as pronounced as when non-host penalties were introduced. Non-host penalties had the greatest effect on the fitness of networks. These results suggest that specialisation should only become an ‘evolutionary dead end’ under very specific and severe conditions.
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Bolnick, Daniel Imara. "Intraspecific competition and niche expansion /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.

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O'Rourke, Eamonn Christopher. "Natural building in South Africa : assessing the niche-regime relationship through a 'latent niche' mediation." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96704.

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Thesis (MPhil)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: In this thesis I examine the natural building movement in South Africa in an attempt to determine the systemic influences that appear to confine it to a small market operating at the very edge of the mainstream building sector. I make use of the conceptual framework of the multi-level perspective to explore the interrelationships between natural building as a technological niche and the mainstream building sector as the dominant regime. I extend the concept of a technological niche by appending the term 'latent' to form the term 'latent technological niche', to describe a technology with sustainability credentials that fails to break into the mainstream market, despite achieving technological maturity and constant though minimal market share. The research objectives of this thesis are to: identify pathways for the natural building niche to move beyond its latent state; to determine how the translations of natural building practices to the building sector might occur; and how this might transform the building sector regime. I explore how action research involving knowledge sharing between multi-stakeholder, niche and regime actors might stimulate debate and subsequent action to overcome entry barriers; and serve as a catalyst to advance a latent technological niche beyond its confined market. I present an action research method, a 'latent technological mediation', of facilitated 1st and 2nd order social learning. This is used as a mechanism of tapping into the immediate knowledge of actors in the socio-technical regime. The purpose being to identify the external forces and internal processes of a latent technological niche. The status of a latent technological niche is assessed by comparing these processes in the context of external forces against seven processes, presented in this thesis. These seven processes are considered crucial for a technology to break into the mainstream market and are adapted from the internal processes of success, described in the literature on strategic niche management and the characteristics of a successful 'bounded socio-technical experiment' (BSTE) described in the conceptual work on BSTE's. The potential for natural building systems to enter the mainstream building sector, particularly in South Africa, is used as a case study to apply the latent technological mediation method. The findings of this research suggest that the mainstream building sector is undergoing a transition following the path of socio-techical transformation. The uncertainty introduced by the parallel system of informal settlement, which may drive transition along the more dramatic technological substitution or de-alignment and re-alignment transition pathways is briefly explored.
AFRIKAANSE OPSOMMING: In hierdie tesis ondersoek ek die natuurlike gebou beweging in Suid-Afrika in 'n poging om die sistemiese invloede te bepaal, wat neig om dit te beperk tot 'n klein mark teen die rand van die hoofstroom gebou sektor. Ek maak gebruik van die konseptuele raamwerk van die multi-vlak perspektief om die onderlinge verband tussen natuurlike geboue, as 'n tegnologiese nis, en die hoofstroom gebou sektor, as die dominante regime, te verken. Ek brei die konsep van 'n tegnologiese nis uit, deur die aanbring van die word 'latente' om die term 'latente tegnologiese nis' te vorm. 'n Latente tegnologie nis het volhoubaarheid potensiaal maar slaag nie daarin om in die hoofstroom mark in te breek nie, ten spyte van die bereiking van tegnologiese volwassenheid en 'n konstante maar minimale mark aandeel. Die navorsing doelwitte van hierdie tesis is om: roetes te identifiseer waarlangs die natuurlike gebou nis buite sy latente toestand kan beweeg; om te bepaal hoe die 'vertalings' van natuurlike gebou praktyke aan die gebou sektor kan voorkom; en hoe dit die gebou sektor regime kan verander. Ek bestudeer hoe aksie navorsing waarby kennis tussen verskeie belanghebbendes, nis en regime betrokkenes gedeel is, kan debatteer en die daaropvolgende aksie stimuleer inskrywing hindernisse te oorkom; en dien as 'n katalisator om 'n latente tegnologiese nis te bevorder buite sy beperkte mark. Ek bied 'n aksie-navorsing metode, 'n 'latente tegnologiese bemiddeling' van gefasiliteerde 1st en 2de order sosiale leerervaring aan. Dit dien as 'n meganisme van deling in die onmiddellike kennis van die spelers in die sosio-tegniese regime. Die doel is om die eksterne kragte en interne prosesse van 'n latente tegnologiese nis te identifiseer. Die status van 'n latente tegnologiese nis is beoordeel deur hierdie prosesse te vergelyk in die konteks van eksterne kragte teen sewe prosesse, wat in hierdie tesis aangebied is. Hierdie sewe prosesse word beskou as noodsaaklik vir 'n tegnologie om in die hoofstroom mark in te breek en is aangepas uit die interne prosesse van sukses, soos beskryf in die literatuur oor strategiese nis bestuur en die eienskappe van 'n suksesvolle 'begrensde sosio-tegniese eksperiment' (BSTE) beskryf in die konseptuele literatuur oor BSTE. Die potensiaal vir natuurlike gebou stelsels om die hoofstroom gebou sektor te betree, veral in Suid-Afrika, word gebruik as 'n gevallestudie om die latente tegnologiese bemiddeling metode toe te pas. Die bevindinge van die navorsing dui daarop dat die hoofstroom gebou sektor 'n verandering ondergaan op die pad van n sosio-tegniese transformasie. Die onsekerheid veroorsaak deur die parallelle informele nedersetting, wat 'n meer dramatiese tegnologiese substitusie, of ontsporing en herbelyning kan veroorsaak, word kortliks ondersoek.
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18

Schmühl, Carina Maria [Verfasser], and Mechanisms of niche adaption by [Akademischer Betreuer] Yersinia. "Mechanisms of niche adaption by Yersinia / Carina Maria Schmühl ; Betreuer: Mechanisms of niche adaption by Yersinia." Hannover : Stiftung Tierärztliche Hochschule Hannover, 2018. http://d-nb.info/1179236947/34.

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19

Lima, Felipe Pontieri de [UNESP]. "Estrutura trófica das assembléia de peixes da represa de Jurumirim, alto rio Paranapanema-SP, Brasil." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/99409.

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Este estudo foi realizado na represa de Jurumirim, alto rio Paranapanema – SP, em três trechos limnologicamente distintos (lótico, transição e lêntico) e em duas lagoas marginais próximas a região de desembocadura do Rio Paranapanema na represa de Jurumirim. O objetivo foi avaliar os padrões relacionados a partilha de recursos alimentares e a estrutura e organização trófica das assembleias de peixes desta represa. Os peixes foram coletados bimestralmente com redes de espera entre abril/2009 e fevereiro/2010. Foram analisados conteúdos estomacais de 24 espécies distribuídas em três ordens e onze famílias quais consumiram no total 50 itens alimentares identificados dispostos em nove categorias tróficas, sendo que os itens principais foram fragmento vegetal, fragmento de peixes e detrito orgânico Os peixes foram classificados mediante a análise de similaridade de acordo com o item preferencial consumido sendo possível reconhecer oito guildas tróficas: Herbívoro, Detritívoro, Piscívoro, Detritívoro/Herbívoro, Insetívoro, Invertívoro e Carcinófago. A guilda dos herbívoros, detritívoros e piscívoros ocorreram em todos os trechos amostrados, sendo a composição em termos de espécie das guildas variável entre os trechos, com nove das 24 espécies estudadas ocorrendo em guildas distintas, indicando flexibilidade na dieta destas espécies. As assembleias de peixes da represa de Jurumirim apresentaram em sua maioria baixos valores de amplitude e sobreposição de nicho trófico, indicando que esta comunidade de peixes partilha os recursos alimentares. Portanto é possível concluir que a ictiofauna da represa de Jurumirim apresenta uma estrutura trófica bem estabelecida, qual as espécies partilham recursos alimentares de forma a evitar competição pelos recursos disponíveis
This study was carried in the Jurumirim Reservoir, Upper Paranapanema River, -SP in three distinct limnologic stretches (lotic, transition, lentic) and two marginal lagoons near the mouth of the Paranapanema river in the Jurumirim Reservoir. The aim was to evaluate the patterns related to food resources partitioning, as well as the trophic structure and organization of fish assemblages. Fish were collected bimonthly with gill nets between April/2009 and February/2010. The stomach contents of 24 species were analyzed, in three orders and eleven families which consumed a total of 50 identified food items arranged in nine trophic categories, with vegetal matter, fragment of fish and organic detritus waste as the main items in the diet of species. Fish were classified by the similarity analysis according to the preferential item consumed, and eight trophic guilds were recognized: herbivorous, detritivorous, piscivorous, detritivorous/herbivorous, insectivorous, invertivorous and carcinophagous. The guild of herbivorous, detritivorous and piscivorous occurred in all sampling sites. The species composition of trophic guilds was variable among sites, with nine of the 24 studied species occurring in different guilds, indicating flexibility in the diet of this species. The fish assemblage of Jurumirim Reservoir showed low niche breadth niche overlap values, indicating that this fish community share food resources. Therefore we conclude that the fish fauna of the reservoir Jurumirim has a well-established trophic structure, which species partitioning food resources to avoid competition
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Lima, Felipe Pontieri de. "Estrutura trófica das assembléia de peixes da represa de Jurumirim, alto rio Paranapanema-SP, Brasil /." Botucatu, 2012. http://hdl.handle.net/11449/99409.

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Orientador: Edmir Daniel Carvalho
Coorientador: Ana Paula Vidotto-Magnoni
Banca: Edmir Daniel Carvalho
Banca: Rosemara Fugi
Banca: Sirlei Therezinha Bennemann
Resumo: Este estudo foi realizado na represa de Jurumirim, alto rio Paranapanema - SP, em três trechos limnologicamente distintos (lótico, transição e lêntico) e em duas lagoas marginais próximas a região de desembocadura do Rio Paranapanema na represa de Jurumirim. O objetivo foi avaliar os padrões relacionados a partilha de recursos alimentares e a estrutura e organização trófica das assembleias de peixes desta represa. Os peixes foram coletados bimestralmente com redes de espera entre abril/2009 e fevereiro/2010. Foram analisados conteúdos estomacais de 24 espécies distribuídas em três ordens e onze famílias quais consumiram no total 50 itens alimentares identificados dispostos em nove categorias tróficas, sendo que os itens principais foram fragmento vegetal, fragmento de peixes e detrito orgânico Os peixes foram classificados mediante a análise de similaridade de acordo com o item preferencial consumido sendo possível reconhecer oito guildas tróficas: Herbívoro, Detritívoro, Piscívoro, Detritívoro/Herbívoro, Insetívoro, Invertívoro e Carcinófago. A guilda dos herbívoros, detritívoros e piscívoros ocorreram em todos os trechos amostrados, sendo a composição em termos de espécie das guildas variável entre os trechos, com nove das 24 espécies estudadas ocorrendo em guildas distintas, indicando flexibilidade na dieta destas espécies. As assembleias de peixes da represa de Jurumirim apresentaram em sua maioria baixos valores de amplitude e sobreposição de nicho trófico, indicando que esta comunidade de peixes partilha os recursos alimentares. Portanto é possível concluir que a ictiofauna da represa de Jurumirim apresenta uma estrutura trófica bem estabelecida, qual as espécies partilham recursos alimentares de forma a evitar competição pelos recursos disponíveis
Abstract: This study was carried in the Jurumirim Reservoir, Upper Paranapanema River, -SP in three distinct limnologic stretches (lotic, transition, lentic) and two marginal lagoons near the mouth of the Paranapanema river in the Jurumirim Reservoir. The aim was to evaluate the patterns related to food resources partitioning, as well as the trophic structure and organization of fish assemblages. Fish were collected bimonthly with gill nets between April/2009 and February/2010. The stomach contents of 24 species were analyzed, in three orders and eleven families which consumed a total of 50 identified food items arranged in nine trophic categories, with vegetal matter, fragment of fish and organic detritus waste as the main items in the diet of species. Fish were classified by the similarity analysis according to the preferential item consumed, and eight trophic guilds were recognized: herbivorous, detritivorous, piscivorous, detritivorous/herbivorous, insectivorous, invertivorous and carcinophagous. The guild of herbivorous, detritivorous and piscivorous occurred in all sampling sites. The species composition of trophic guilds was variable among sites, with nine of the 24 studied species occurring in different guilds, indicating flexibility in the diet of this species. The fish assemblage of Jurumirim Reservoir showed low niche breadth niche overlap values, indicating that this fish community share food resources. Therefore we conclude that the fish fauna of the reservoir Jurumirim has a well-established trophic structure, which species partitioning food resources to avoid competition
Mestre
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CORRÊA, Daniele Niedsberg. "Ecologia alimentar das serpentes semi-aquáticas Erythrolamprus jaegeri jaegeri (Günter, 1858) e Erythrolamprus poecilogyrus sublineatus (Cope, 1860) (Serpentes, Dipsadidae) na região costeira do extremo sul do Brasil." reponame:Repositório Institucional da FURG, 2014. http://repositorio.furg.br/handle/1/6031.

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Predadores exclusivamente carnívoros, as serpentes alimentam-se de presas variadas e ocupam diferentes hábitats. As adaptações evolutivas conferidas aos ofídios permitiram o desenvolvimento de múltiplos mecanismos de percepção da presa, modo de captura e estratégias que permitem a ingestão de presas bem maiores que seu próprio tamanho. Erythrolamprus jaegeri jaegeri e Erythrolamprus poecilogyrus sublineatus são serpentes semi-aquáticas que ocorrem em simpatria no extremo sul do Brasil. O presente estudo teve como objetivo analisar a composição da dieta dessas duas espécies e, mediante contrastes, investigar os fatores associados a essas diferenças. Para isso, foram utilizados exemplares provenientes da região de estudo, depositados em coleção Herpetológica da FURG (CHFURG). Os itens alimentares foram coletados, identificados ao menor nível taxonômico possível e medidos. Adicionalmente, todas as serpentes tiveram estruturas do corpo e da cabeça mensurados. Os itens alimentares foram analisados segundo métodos qualitativos e quantitativos como Frequência de Ocorrência (FO%), Abundância Numérica (N%), Análise Gravimétrica (P%) e Índice de Importância Relativa (IRI). Os itens mais importantes para ambas as espécies foram os anuros. Diferenças na composição da dieta e o índice de Levins indicaram um caráter especialista para E. j. jaegeri e generalista para E. p. sublineatus. E. p. sublineatus é estatisticamente maior do que E. j. jaegeri e se alimenta de itens maiores. Segundo as análises de regressão, as estruturas da cabeça parecem não interferir no tamanho das presas selecionadas, enquanto isso foi observada correlação positiva entre o comprimento e o peso de predadores e presas para as duas espécies. Os resultados indicaram que, apesar de simpátricas, a composição alimentar das espécies diverge segundo dois parâmetros: o tamanho do corpo do predador que está associado ao tamanho das presas selecionadas e a diferente amplitude de nicho de cada espécie, ambos permitindo que os recursos utilizados variem entre as espécies, diminuindo a competição e possibilitando a coexistência.
Exclusively carnivorous predators, snakes feed on various prey and occupy different habitats. The evolutionary adaptations conferred on snakes allows the development of multiple mechanisms that are the perception of the prey, capture mode and strategies that allow the ingestion of larger prey. Erythrolamprus jaegeri jaegeri and Erythrolamprus poecilogyrus sublineatus are semi-aquatic snakes which live on the extreme southern Brazil. This study aimed to compare the diet of these two species and also investigate the factors associated with these differences. To performes this study we use specimens from Herpetological Collection from FURG (CHFURG). Food items were collected, identified and measured, including snakes that had injured body structures. Food items were analyzed according to the qualitative and quantitative methods as Frequency of Occurrence (FO%), Numerical abundance (% N), Gravimetric Analysis (P%) and Index of Relative Importance (IRI). The most important prey for both species were anurans. The comparison of differences in the diet and the Levins index indicated that E. j. jaegeri is specialist and E. p. sublineatus is generalist. The bar graphs to the length and weight of the predators and prey showed that E. p. sublineatus is statistically larger than E. j. jaegeri and prey on larger animals. According the regressions analysis, the structures of the head do not seem to interfere with the size of the selected prey, meanwhile positive correlation was observed between the length and weight of predators and prey for both species. Results indicated that although sympatric, food species composition differs according to two parameters: the body size of the predator that is associated with the size of the selected prey and different range of each species niche, allowing both the resources used to vary between species, reducing competition and allowing coexistence.
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MUNIZ, Sérgio Luiz da Silva. "Diversidade e uso do microhábitat de lagartos em uma região do domínio das caatingas, Nordeste do Brasil." Universidade Federal Rural de Pernambuco, 2013. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/5271.

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Of all Squamata diversity, lizards represent more than half of described species in present. These animals serve as models for ecological and evolutionary studies, which makes them target of interest in scientific research in whole world. Caatinga is a major biome in Northeast of Brazil, occupying about 6.83% of the national territory and extending for several states of this region. It is a unique biome, and despite being located on a semi-arid climate, has a great variety of landscapes, biological richness and endemism. Reptile’s studies of diversity, composition and ecology in Caatinga are relatively recent, these research are extremely important and valuable to semiarid. But this information is punctual and does not represent Northeast biodiversity, requiring more effort in different localities, especially in rainforest areas of biome. This study aims to investigate lizard’s abundance, richness, diversity, spatial distribution and width/niche overlap in the Environmental Protection Area of Araripe. To achieve this goal, we sampled three different vegetation types (shrubby Caatinga, Cerradão and secondary Forest) APA of Chapada Araripe. The data collections were made monthly by active and passive collecting, during the twelve-month period (August/2011 to July/2012). The active collection was made one day for each area per month and lasting for six hours a day, three hours in the morning (8h to 11h), and three hours at night (18 to 21h). The passive collections were made using 60 pitfall traps with drift-fences, these were organized into twelve lines with five buckets at 5m of distance between them, and the lines were equally distributed at three vegetation types. Buckets were open for five days during each month. As a result, we found 20 lizard species belonging to 12 families. Richness and abundance varied among the three areas sampled. Caatinga had the highest number of species (n = 14) and Cerradão had de highest abundance (n = 99). Ameiva ameiva was the most abundant lizard from caatinga, while in Cerradão was Colobosaura modesta and for secondary forest was Norops brasiliensis. Lizards presents significant difference respect to the seasons (wet and dry), in the dry season the lizards were more abundant. Analyses based on null models indicate no significant values on the overlap of microhabitat use, showing that competition for space is not regulating this community structure, being regulated by other factors.
De toda diversidade da ordem Squamata, os lagartos representam um pouco mais que a metade das espécies descritas na atualidade. Esses animais são organismos modelos para estudos ecológico-evolutivos, o que faz com que sejam alvo de interesse de pesquisas científicas em vários lugares do mundo. A Caatinga é um dos principais biomas da região Nordeste do Brasil, ocupa cerca de 6,83% do território nacional e estende-se por vários estados dessa região. É um bioma único, e apesar de estar localizado em área de clima semiárido, apresenta grande variedade de paisagens, relativa riqueza biológica e endemismos. Estudos acerca da diversidade, composição e ecologia dos répteis da Caatinga são relativamente recentes, esses trabalhos são extremamente importantes e de grande valor para entendere e preservar o semiárido. Porém essas informações são pontuais e não representam ainda a biodiversidade da região Nordeste, necessitando de mais esforços em diferentes localidades, principalmente em áreas de floresta úmida inseridas nesse bioma. Este trabalho objetiva investigar a abundância, riqueza, diversidade, distribuição espacial e largura/sobreposição de nicho dos lagartos da Área de Proteção Ambiental da Chapada do Araripe. Para alcançar esse objetivo, foram amostradas três diferentes fitofisionomias (Caatinga arbustiva, Mata de encosta e Cerradão) da APA da Chapada do Araripe. As coletas de dados foram feitas através de coletas ativas e passivas realizadas mensalmente durante o período de doze meses (Agosto/2011 a Julho/2012). A coleta ativa foi realizada durante um dia para cada área por campanha e com duração de seis horas diárias, sendo três horas no período matutino (8 às 11h), e três horas no período noturno (18 às 21h). As coletas passivas foram realizadas através de 60 baldes distribuídos nas armadilhas de contenção e queda (pitfall), com cercas guias (drift-fences), estas foram organizadas em doze linhas de cinco baldes, com 5m de distância entre os mesmos, e as linhas foram distribuídas igualmente nas três fitofisionomias estudadas, onde os baldes permaneceram abertos por cinco dias durante cada campanha. Como resultado, foi registrado 20 espécies de lagartos, pertencentes a 12 famílias. A riqueza e abundância variaram entre as três áreas amostradas. A área de caatinga foi a que obteve o maior número de espécies (n= 14) e a área de cerradão foi a mais abundante (n= 99). O lagarto mais abundante na área de caatinga foi Ameiva ameiva, na área do cerradão Colobosaura modesta e para a área da Mata secundária Norops brasiliensis. Houve diferença significativa entre as estações (chuvosa e seca), na estação seca os lagartos foram mais abundantes. As análises baseadas em modelos nulos indicam valores não significativos sobre a sobreposição do uso do microhábitat, evidenciando que a competição por espaço não está regulando a estrutura das comunidades estudadas, sendo ela regulada por outros fatores.
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Horner, Hervé. "« Niche Writers » : Une étude sociologique des niches sociales d’auteurs à New York et à Paris." Thesis, Paris 5, 2012. http://www.theses.fr/2012PA05H045.

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Ce projet de recherche a pour but d’étudier le processus créatif, l’apprentissage social, la rationalité, les conflits, les règles et les normes de trois groupes d’auteurs contemporains à New York et à Paris. Les méthodes de recherche incluent des entretiens avec des auteurs, la narration d’anecdotes sur le comportement des acteurs sociaux, la construction d’un tableau sociométrique des règles et des normes propres à chaque groupe d’après la théorie de Howard BECKER, et une analyse de texte qui mobilise la méthode d’étude structurale du sociologue de la littérature Lucien GOLDMANN. Ce projet de recherche a permis l’identification des niches sociales d’auteurs contemporains, dans lesquelles des échanges d’informations permettent un apprentissage social qui a de la valeur professionnelle et personnelle pour les acteurs sociaux en question. Enfin, ce projet de recherche permettra le placement des auteurs contemporains dans l’organigramme de la production culturelle de Pierre BOURDIEU, qui distingue « le sous-champ de l’avant-garde », « le sous-champ de la grande production » et « le champ du pouvoir » dans le monde littéraire
The purpose of this research project is to explore the creative process, social learning, motivation, conflicts, rules and norms of three groups of contemporary writers in New York and Paris. Research methods include interviews with authors, the narration of anecdotes about the behavior of the social actors, and the construction of a sociometric table of rules and norms specific to each group according to the theory of Howard BECKER. This project also offers contains a literary analysis using Lucien GOLDMANN’s method of structural study. This research led to the identification of social networks of contemporary authors, in which the exchange of information allows social learning that has both professional and personal value for the social actors in question. Finally, this research will allow the placement of contemporary authors into Pierre BOURDIEU’s map of cultural production, which distinguishes “the sub-field of the avant-garde,” “the sub-field of large-scale production,” and “the field of power” in the literary world
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von, Fahnestock Frank Michael. "Niche applications of in-vessel composting." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1127237412.

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Thesis (Ph. D.)--Ohio State University, 2005.
Title from first page of PDF file. Document formatted into pages; contains xvii, 233 p.; also includes graphics (some col.). Includes bibliographical references (p. 185-192). Available online via OhioLINK's ETD Center
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Pocheville, Arnaud. "LA NICHE ÉCOLOGIQUE: CONCEPTS, MODÈLES, APPLICATIONS." Phd thesis, Ecole Normale Supérieure de Paris - ENS Paris, 2010. http://tel.archives-ouvertes.fr/tel-00715471.

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Cette thèse est une enquête sur le concept de niche et quelques grands cadres théoriques qui y sont apparentés: la théorie de la niche et la théorie neutraliste en écologie, la théorie de la construction de niche en biologie évolutive, et la niche des cellules souches en écologie intra-organisme. Le premier chapitre retrace l'histoire du concept de niche et confronte la théorie de la niche à une théorie concurrente, la théorie neutraliste. Le concept de niche apparaît comme devant être un explanans de la diversité des espèces et de la structure des écosystèmes. Le deuxième chapitre confronte la théorie évolutive standard à la théorie de la construction de niche, dans laquelle un organisme peut modifier son environnement et ainsi influer sur la sélection à venir. Nous montrons comment caractériser cette confrontation en termes d'échelles temporelles des processus en jeu, ce qui nous permet d'identifier le domaine de validité véritablement propre à la théorie de la construction de niche plus explicitement qu'il ne l'a été par le passé. Le troisième chapitre développe les recherches des deux chapitres précédents dans le cadre de la modélisation d'une thérapie génique comme un processus écologique de compétition et de construction de niche par les cellules. Nous présentons une famille de modèles appliqués à différentes échelles temporelles de la dynamique cellulaire, entre lesquelles le modélisateur précautionneux ne saurait choisir sans résultats expérimentaux spécifiques. Nous concluons sur les conceptions de la relation entre un organisme et son environnement attachées aux diverses facettes du concept.
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26

Hagisako, Takahiro. "Niche strategies in the healthcare industry." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111467.

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Thesis: M.B.A., Massachusetts Institute of Technology, Sloan School of Management, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 32-33).
This paper examines niche strategies in the healthcare industry. I begin by discussing productivity trends in large firms. In order to understand trend shifts in productivity from a focus on output to a focus on input, I examine the competitive strategy frameworks of Duncan Simester of MIT, and Michael Porter of Harvard, and then apply these frameworks to the healthcare industry. That foundation allows me to develop the framework for a niche strategy. There are two input reduction strategies, and I discuss each one based on the niche strategy framework. I also examine the role of healthcare start-ups and compare them with startups in other industries. Finally, I compare the growth strategies of incumbent large firms and start-ups in the healthcare industry.
by Takahiro Hagisako.
M.B.A.
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27

Janse, Van Vuuren Adriaan. "Niche Occupation in Biological Species Competition." Thesis, Stellenbosch : University of Stellenbosch, 2008. http://hdl.handle.net/10019.1/2932.

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Thesis (MSc (Logistics))--University of Stellenbosch, 2008.
The primary question considered in this study is whether a small population of a biological species introduced into a resource-heterogeneous environment, where it competes for these resources with an already established native species, will be able to invade successfully. A two-component autonomous system of reaction-diffusion equations with spatially inhomogeneous Lotka-Volterra competitive reaction terms and diffusion coefficients is derived as the governing equations of the competitive scenario. The model parameters for which the introduced species is able to invade describe the realized niche of that species. A linear stability analysis is performed for the model in the case where the resource heterogeneity is represented by, and the diffusion coefficients are, two-toned functions. In the case where the native species is not directly affected by the resource heterogeneity, necessary and sufficient conditions for successful invasion are derived. In the case where the native species is directly affected by the resource heterogeneity only sufficient conditions for successful invasion are derived. The reaction-diffusion equations employed in the model are deterministic. However, in reality biological species are subject to stochastic population perturbations. It is argued that the ability of the invading species to recover from a population perturbation is correlated with the persistence of the species in the niche that it occupies. Hence, invasion time is used as a relative measure to quantify the rate at which a species’ population distribution recovers from perturbation. Moreover, finite difference and spectral difference methods are employed to solve the model scenarios numerically and to corroborate the results of the linear stability analysis. Finally, a case study is performed. The model is instantiated with parameters that represent two different cultivars of barley in a hypothetical environment characterized by spatially varying water availability and the sufficient conditions for successful invasion are verified for this hypothetical scenario.
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28

Janse, van Vuuren Adriaan. "Niche occupation in biological species competition /." Link to the online version, 2008. http://hdl.handle.net/10019/753.

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29

Morley, L. "Niche-adaptive evolution in Campylobacter jejuni." Thesis, Nottingham Trent University, 2014. http://irep.ntu.ac.uk/id/eprint/27913/.

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Campylobacter jejuni is the leading causative agent of human bacterial gastroenteritis. Human C. jejuni infection (campylobacteriosis) is frequently associated with poultry; through consumption of undercooked products, cross contamination from raw meats, or through direct contact with birds or their faecal matter, however it is established that poultry is not the sole cause of C. jejuni infection in humans. This research reveals new information on the MLST ST403 Clonal Complex, a previously identified C. jejuni lineage associated with the porcine host. ST403CC C. jejuni have also been linked with other mammalian hosts to a lesser degree, and have been implicated in human campylobacteriosis, however to date this clonal complex has not been linked to poultry. The original hypothesis of this research predicted that due to sharing a host niche commonly associated with C. coli, the porcine ST403CC may show evidence of increased recombination with C. coli, however this was not observed. Six ST403CC isolates of porcine origin were subjected to phenotype testing and whole genome sequencing; these isolates were capable of invasion in vitro, and were revealed both to have acquired seemingly lineage specific content, in the form of Restriction-Modification (R-M) system associated genes, and to have undergone degredation of certain loci. The ST403CC isolates also exhibited a distinct pattern of reduced genomic recombination compared to non-ST403CC C. jejuni, with evidence of lineage specific recombination events. Both generalist & specialist lineages have previously been revealed in C. jejuni. The research presented here identifies a new specialist lineage which is associated with mammalian hosts, and not found in poultry.
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30

Yguel, Benjamin. "Sortir de sa niche ancestralele cas du chêne sessile et pédonculé : conséquences pour les interactions biotiques : le cas du chêne sessile et pédonculé." Rennes 1, 2012. http://www.theses.fr/2012REN1S142.

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Le conservatisme phylogénétique de niche se définit par la conservation, au cours du temps, de la niche écologique et des traits écologiques associés. Des espèces phylogénétiquement proches auront alors tendances à occuper des niches similaires, incluant des conditions abiotiques mais aussi des interactions biotiques similaires. Ainsi, un individu isolé phylogénétiquement de ses voisins, pourrait être considéré comme présent dans une nouvelle niche. Dans cette thèse, nous nous sommes intéressés aux interactions trophiques des individus de plantes hôtes colonisant une nouvelle niche, représentée par un voisinage phylogénétiquement éloigné, à la différence des individus hôtes restant dans leur niche ancestrale. Nous avons étudié plus particulièrement le cas du chêne et de ses phytophages, de leurs ennemis naturels, et enfin, des ectomycorhizes du chêne. Nos résultats indiquent que l'isolement phylogénétique des chênes hôtes (i) diminue l'abondance des phytophages et leurs pressions sur le chêne, (ii) diminue la pression des ennemis spécialistes sur ces phytophages, (iii) augmente l'abondance et l'activité des ectomycorhizes du chêne. Plus généralement, nos résultats permettent de discuter dans quelles situations une sortie de niche sera favorisée et dans quelles situations, une sortie de niche sera contrariée. Ces résultats suggèrent que les chênes phylogénétiquement isolés, mais aussi leurs phytophages et leurs mycorhizes, subissent des pressions de sélection particulières qui pourraient être à l'origine d'une différentiation évolutive à long terme
Niche conservatism is defined as the conservation of the niche and its associated ecological traits over time. Thus, phylogenetically closely related species tend to occupy similar niches, including abiotic conditions but also biotic interactions. Hence, individuals surrounded by phylogenetically distantly related species could be considered as inhabitant of new niche. In this thesis we were interested in trophic interactions of host individuals inhabiting a new niche, represented by distantly related neighbours, as compared to hosts remaining in their ancestral niche. We studied oak hosts and their phytophages, the next trophic level, i. E. The oak phytophages and their natural enemies, and finally the ectomycorhizal fungi of oaks. Our results showed that phylogenetic isolation of oak hosts (i) decreases abundance and pressure of phytophages on oak hosts, (ii) decreases enemy pressure of specialized enemies on oak phytophages, (iii) increases ectomycorhizal fungi abundance and activity. Hence, our results indicate that phylogenetic isolation of oaks changes the intensity and the nature of biotic interactions all along the entire trophic chain based on oaks. Our results allow us to discuss the biotic forces that favor or impede the colonization of a new niche. Moreover, we suggest that phylogenetically isolated oaks, their phytophages and their ectomycorhizal mutualists undergo specific selective pressures that could trigger evolutionary differentiation in long term
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31

Monnet, Anne-Christine. "Apport des modèles de niche aux translocations d'espèces : cas du renforcement de populations d'Outarde houbara." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066655/document.

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Les modèles de niche écologique (ENM) sont largement utilisés pour prédire la distribution actuelle et future des espèces. Ils peuvent être des outils complémentaires pour évaluer la qualité de niche des potentielles aires de lâchers, un facteur clé pour le succès des translocations. Pourtant, les ENM sont encore rarement appliqués dans les translocations et on a encore peu de preuves de leur intérêt pour les translocations. Nous avons centré nos recherches sur des programmes bien établis de renforcement des populations de deux espèces d'Outarde houbara, l'espèce nord-africaine (Chlamydotis undulata) et l'espèce migratrice asiatique (C. macqueenii). Grâce à un suivi intensif de populations sauvages relictuelles et d'individus élevés en captivité et lâchés sur une large partie de leur aire de répartition, ces programmes fournissent un cadre d'étude idéal pour envisager des questions complexes sur la pertinence des ENM dans la translocation. Nous avons relié la survie individuelle, une composante essentielle de la dynamique des populations, à la qualité de niche, en réalisant notamment un lâcher expérimental de 180 individus le long du gradient de qualité de la niche. Nous avons ensuite testé si les outardes lâchées utilisent la même niche écologique que les sauvages pour valider l'utilisation ultérieure des projections des modèles. Enfin, nous discutons de l'implication des changements globaux pour les translocations d'Outarde houbara. Ces approches empiriques reliant la qualité de niche aux processus démographiques constituent un pas en avant pour une meilleure compréhension de la pertinence des ENM pour les translocations d'espèces dans un environnement changeant
Ecological niche models (ENM) are widely used to predict the current and future distribution of species. They could be used as complementary tools to assess the niche suitability of potential release areas, a key parameter for improving success in conservation translocation. Yet, ENM are still rarely applied and general evidence about the benefit of these models in translocation is still lacking. We focused our research on reinforcement programs of two species of Houbara Bustard, the sedentary North African species (Chlamydotis undulata undulata) and the migratory Asian species (C. macqueenii). Through the extensive monitoring of remnant wild populations and captive-born released individuals over a large proportion of their distribution range, these programs provide an ideal study framework to address complex questions regarding the relevancy of ENM in translocation conservation. First, we linked individual survival, a crucial component of population dynamics, to niche suitability. Then, we performed an experimental release and monitoring of 180 individuals along a gradient of habitat suitability as predicted by ENM to test the effect of release site suitability on survival of captive-born individuals. We then tested if released houbaras use the same ecological niche than wild houbaras, as a validation step to support the subsequent use of niche modelling. Finally, we discussed the implications of global change for ongoing translocation programs of Houbara Bustard. Empirical approaches linking habitat suitability with demographic processes provide a step towards a better understanding of the relevance of ENM for conservation translocations in changing environments
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32

Reis, Andressa da Silva. "Ecologia trófica e ecomorfologia da ictiofauna de igarapés maranhenses." Universidade Federal de São Carlos, 2011. https://repositorio.ufscar.br/handle/ufscar/2050.

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The trophic ecology is one of the most important aspects to understand the role of a species in the community and in the ecosystem functioning. Studies regarding the feeding of fishes coupled to the ecomorphology of a species become important tools in understanding their ecological role and position in the environment. The present study aimed to analyze the types and amount of food consumed by eleven species of fishes collected in six streams of Alcântara, Maranhão state, and assess their possible interspecific interactions. The specimens were collected in the rainy season, in January, and in the dry season, in November 2008. The analysis of morphology of the fish species was performed by measuring 17 characteristics and calculating 16 ecomorphological attributes. Analysis of the contents of the digestive tract was performed quantitatively and qualitatively. In order to determine the feeding habits of each species the frequency of occurrence, volume and alimentary index of each food item consumed were calculated. The majority of individuals analyzed was collected in the streams Igarapé do Camarajó and Igarapé do Brito. The trophic structure of fish assemblages of these two streams was diversified in both, rainy and dry seasons. The habit of the benthivore species Micropoecilia cf. parae and Apistogramma cf. piauienses was corroborated by their morphology. In the rainy season, there was a higher niche overlap in the diet of insectivorous species in the stream Igarapé do Camarajó, but the morphology of these species showed distinct spatial occupation of the habitat, thus allowing their coexistence. In the dry season most species had food overlap due to the consumption of organic detritus in the Igarapé do Camarajó stream and due to the consumption of chironomid larvae in the Igarapé do Brito stream. Fishes of Camarajó and Brito streams were more likely to feeding specialization in the rainy season and increased diversification of the items consumed during the dry season, indicated, respectively, by larger and smaller niche breadth. The changes in the trophic structure, in the niche overlap and in the niche breadth of fish community in the six streams studied indicate that fluctuations on the hydrological cycle in these streams are an important factor in the throphic dynamics of these fish communities.
Um dos aspectos mais relevantes no entendimento do papel de uma espécie na comunidade à qual pertence e no funcionamento nos ecossistemas refere-se à sua ecologia trófica. Estudos sobre a alimentação de peixes atrelados à ecomorfologia das espécies são ferramentas importantes no entendimento do papel ecológico das espécies e de sua ocupação do meio. O presente estudo teve como objetivos estudar as características da alimentação e da ecomorfologia da ictiofauna amostrada em seis igarapés maranhenses e avaliar suas possíveis interações interespecíficas. Os exemplares analisados foram coletados na estação chuvosa, em janeiro, e na estação seca, em novembro, de 2008. Para análise da ecomorfologia destas espécies foram obtidas 17 medidas e com elas calculados 16 atributos ecomorfológicos. A análise do conteúdo do tubo digestório foi realizada quali e quantitativamente. Para a determinação do hábito alimentar de cada espécie foram calculados a frequência de ocorrência, o volume e o índice alimentar de cada item consumido. A maioria dos indivíduos analisados foi coletada nos igarapés do Camarajó e do Brito. A estrutura trófica da assembléia de peixes destes dois igarapés foi diversificada em ambas estações, chuvosa e seca. O hábito bentófago das espécies Micropoecilia cf. parae e Apistogramma cf. piauiensis foi corroborada por suas morfologias. Na estação chuvosa, observou-se maior sobreposição de nicho na dieta dos insetívoros no igarapé do Camarajó, porém, os atributos ecomofológicos destas espécies indicaram distinta ocupação de nicho espacial entre elas, permitindo, assim, a coexistência. Já na estação seca, no igarapé do Camarajó, a maioria das espécies teve sobreposição alimentar devido ao consumo de detritos orgânicos e no igarapé do Brito pelo consumo de quironomídeos. Os peixes dos igarapés do Camarajó e do Brito apresentaram maior tendência à especialização alimentar na estação chuvosa e maior diversificação dos itens consumidos na estação seca, ambas indicadas pela maior e menor amplitude de nicho, respectivamente. As mudanças na estrutura trófica, na sobreposição e no espectro alimentar da ictiofauna dos seis igarapés maranhenses estudados, indicam que as flutuações decorrentes do ciclo hidrológico constituem, nestes igarapés, um fator importante na dinâmica destas comunidades de peixes.
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33

Favalesso, Marília Melo. "Condições ecológicas e predição de áreas adequáveis para ocorrência de Lonomia obliqua Walker 1855 no Brasil." Universidade Estadual do Oeste do Paraná, 2018. http://tede.unioeste.br/handle/tede/3961.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Lonomia obliqua Walker 1855 (Saturniidae: Hemileucinae) is a species of moth of sanitary interest in Brazil. Their larvae are etiological agents of lonomism, a form of erucism caused by the contact of the human beings with the stinging structures of the species. The most worrying symptoms of lonomism are the systemic hemorrhagic conditions that can lead to several outcomes, including death. The first official notifications of accidents with the species date back to the end of the 80s, in the state of Rio Grande do Sul. Since then, several accidents have been documented in Brazil, mainly in the south and southeast regions of the country. With the increase in the number of victims, health authorities in the state of São Paulo, represented by the “Instituto Butantã”, developed an anti-lonomic serum, which is distributed by the Ministry of Health in places with a higher prevalence of accidents. Hypotheses have been raised on the relation between the growth of the cases of lonomismo and the human occupation; however, little is known about the spatial distribution and ecological aspects of the species to enable the testing of these hypotheses. In view of the above, the present study aimed to produce a map for the potential geographical distribution of L. obliqua in Brazil, based on the combination of different ENM (Ecological Niche Modeling) algorithms. A total of 38 occurrence points were distributed across the geographic area of Brazil and Misiones, Argentina, which were partitioned for calibration and evaluation of the distribution model. Eight continuous climatic variables and only 16 previously considered variables were selected. Different ENM methodologies were tested and compared to TSS (True Skill Statistic) index values. The final model-map was composed of a combination of four algorithms (Gower, Mahalanobis, Maxent and SVM), with pseudo-absences outside a bioclimatic envelope and a number of pseudo-absences equal to that of presences. This model map was binarized from the Low Presence Threshold (LPT) and cut only for Brazil. According to this model map, the areas predicted as suitable for L. obliqua would be restricted to latitudes ~12° and ~32°, and longitudes ~39° and ~57°. When evaluating new sites of occurrence of the specie in Rio Grande do Sul, it was possible to verify that all the municipalities were in areas predicted by the model-map. A characterization of the abiotic variables related to the niche of the specie was also carried out, being these extracted from the area predicted as adequate the presence of the specie in the model map. To help characterize these variables, we also extract categorical descriptors of climate, soil and vegetation (in %). The percentage of land use classes was also extracted in order to contribute to the hypothesis that condition the increase of accidents due to human occupation. In this question, we find a large part of the area predicted within classes of agricultural soils in Brazil, which leads us to ratify the current hypotheses. Thus, the loss of habitat of the species for the agricultural enterprises increases the human contact with the specie, which should increase the number of notifications of the lonomism, generating greater epidemiological concern and habitat conservation for this specie.
Lonomia obliqua Walker 1855 (Saturniidae: Hemileucinae) é uma espécie de mariposa de interesse sanitário no Brasil. Suas larvas são agentes etiológicos do lonomismo, uma forma de erucismo causado pelo contato dos seres humanos com as estruturas urticantes da espécie. Os sintomas mais preocupantes do lonomismo são os quadros hemorrágicos sistêmicos que podem conduzir a diversos desfechos, inclusive o óbito. As primeiras notificações oficiais de acidentes com a espécie datam do final da década de 80, no estado do Rio Grande do Sul. A partir de então, diversos acidentes têm sido documentados no Brasil, principalmente nas regiões sul e sudeste do país. Com o aumento do número de vítimas, autoridades sanitárias do estado de São Paulo, representadas pelo do Instituto Butantã, desenvolveram um soro antilonômico, o qual é distribuído pelo Ministério da Saúde em localidades com maior prevalência de acidentes. Hipóteses têm sido levantadas sobre a relação entre o crescimento dos casos de lonomismo e a ocupação humana; contudo, pouco se conhece sobre a distribuição espacial e aspectos ecológicos da espécie para possibilitar os testes destas hipóteses. Diante do exposto, o presente estudo objetivou produzir um mapa para a distribuição geográfica potencial de L. obliqua no Brasil, baseando-se na combinação de diferentes algoritmos ENM (Ecological Niche Modeling). Foram utilizados 38 pontos de ocorrência distribuídos pela área geográfica do Brasil e região de Misiones, na Argentina, os quais foram particionados para calibração e avaliação do modelo de distribuição. Foram selecionadas oito variáveis contínuas climáticas e de solo entre 16 previamente cogitadas. Diferentes metodologias ENM foram testadas e confrontados quanto a valores de índice TSS (True Skill Statistic). O mapa-modelo final foi composto por uma combinação de quatro algoritmos (Gower, Mahalanobis, Maxent e SVM), com amostragens de pseudo-ausências fora de um envelope bioclimático e número de pseudo-ausências igual ao de presenças. Esse mapa-modelo foi binarizado a partir do limiar LPT (Lowest Presence Threshold) e recortado somente para o Brasil. Segundo este mapa-modelo, as áreas preditas como adequáveis a L. obliqua estariam restritas as latitudes ~12º e ~32º, e as longitudes ~39º e ~57º. Também foi realizada uma caracterização das variáveis abióticas relacionadas ao nicho da espécie, sendo essas extraídas da área predita como adequada a presença da espécie no mapa-modelo. O percentual de classes de uso da terra também foi extraído, a fim de contribuir com as hipóteses que condicionam o aumento de acidentes em função da ocupação humana. Neste quesito, encontramos grande parte da área predita dentro de classes de solos agrícolas no Brasil, o que nos leva a ratificar as hipóteses atuais. Assim, a perda de habitat da espécie para os empreendimentos agrícolas aumenta o contato humano com a espécie, o que deve aumentar o número de notificações do lonomismo, gerando maior preocupação a nível epidemiológico e de conservação de habitat para essa espécie.
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34

MacLean, Adam L. "Modelling haematopoietic stem cells in their niche." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24927.

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Modelling haematopoietic stem cells (HSCs) mathematically allows us to probe their behaviour, test hypotheses and make predictions. HSCs are essential and elusive; despite many recent advances much remains unknown, including how the microenvironment (niche) influences HSC behaviour, and the nature of complex interactions between HSCs, the niche and disease. This thesis comprises three sections. In the first we present new methods for the analysis of ODE systems that allow us to characterise steady state properties such as the probability of a state being stable (over some parameter range). We apply these methods to models of stem cell dynamics that differ in the form of regulation (feedback) imposed on the system and study the steady states of these systems. Competition within the niche between HSCs and invading cancer cells disrupts the system. In the second section we model this using ODEs that describe the population dynamics of cellular species from an ecological perspective. From the analysis of two models differing in their treatment of the niche, using Bayesian inference, we find that maintaining a viable HSC population is necessary and almost sufficient in order to outcompete leukaemia and restore healthy haematopoiesis. In the third section we extend the analysis of interactions between HSCs, leukaemia and the niche: performing a comparison of three models that describe the dynamics of chronic myeloid leukaemia. We study heterogeneous data from a clinical trial of the disease. All models fit these data, but do so in different ways. One model is discarded due to its unrealistic predictions, suggesting that direct competition between species is important. Each of the remaining two models makes testable predictions, but validating these is at current experimental limits. In the future, the results presented will aid experimental design and provide a framework from which to identify new therapeutic targets for haematopoietic diseases.
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35

Wang, Alice Chun-Yin. "Amino acid metabolism in the inflammatory niche." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/28572.

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Stroma and parenchyma represent the supportive and functional components in every organ of the body, respectively. Beyond their ability to produce structural support and to differentiate into tissues of mesodermal origin, mesenchymal stromal cells (MSC) exhibit potent immunomodulatory properties. Such a function requires an activation step ('licensing signal') provided by the inflammatory microenvironment to which MSC are exposed. My results have attributed immunosuppressive effects of MSC to essential amino acid (EAA) deprivation. Amongst the EAA consuming enzymes examined, blocking nitric oxide synthase 2 (NOS2) and histidine decarboxylase (HDC) both resulted in impaired anti-proliferative activity of MSC, while NOS2 appeared to be a more prominent effector. My results have also demonstrated that TNF-α and IFN-γ differently account for NOS2 and HDC up-regulation, respectively. Furthermore, MyD88 and NF-κB were identified as upstream mediators for initiating NOS2 production. The role of TNF-α and NOS2 in MSC-mediated immunosuppression was assessed in vivo using a murine model of peritonitis. MSC treatment remarkably reduced the local inflammatory response during acute peritoneal inflammation. Nevertheless, both Nos2-/- and Tnfr1/r2-/- MSC delivered similar effects compared to WT MSC, indicating the presence of other complementary mechanisms in MSC-mediated immunosuppression in vivo. In addition to their immunomodulatory properties, MSC are fundamental in regulating self-renewal and differentiation of haematopoietic stem cells (HSC). MSC protect HSC from potential damage by maintaining their quiescence. My results have revealed that the ability of MSC to enhance the quiescence of HSC was associated with cell-cycle arrest induced by NOS2. As striking parallels exist between the normal and malignant stem cell niche, I investigated the ability of MSC to protect haematopoietic malignant cells from chemotherapy-induced apoptosis. MSC were observed to confer protection from etoposide-induced necrosis of EL4 cells, possibly due to their ability to suppress EL4 proliferation. Collectively, my results have demonstrated the role of MSC across the fields of immunomodulation, niche-supporting and anti-apoptotic effects.
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36

Bublys, Kasparas. "Diet variability in Eurasian perch (Perca fluviatilis) as a response to environmental variables along a latitudinal gradient." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-365794.

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Climate change is expected to have a profound impact on freshwater fish communities, especially at higher latitudes. In this study I investigated potential effects of climate change on the niche structure of Eurasian perch (Perca fluviatilis) by looking at their diet across a latitudinal gradient and at varying light climate. Dietary niche width of Eurasian perch did not differ significantly between boreal and temperate latitudes. Additionally, no significant difference in the prevalence of specialist individuals was found along the latitudinal gradient and water transparency levels. Habitat was the main factor that significantly affected niche width and level of specialization with both being significantly higher in the littoral habitat. Taken together my results suggest that climate change might indirectly affect niche patterns by altering fish densities through changes in productivity resulting in niche and specialization variation among habitats.
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37

Rettig, Adam V. "Associations between benthic fishes and habitat at multiple spatial scales in headwater streams of the Missouri Ozarks /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p1418059.

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Cruz, Leonardo Dominici. "Nicho trofico de Gracilinanus microtarsus (Didelphimorphia: Didelphidae) : variação intra-populacional e inter-individual." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/316227.

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Orientador: Sergio Furtado dos Reis
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: A teoria do nicho ocupa uma posição central na Ecologia, tendo um papel fundamental nos modelos de dinâmicas populacionais e de comunidades. Apesar disso, sua formalização tradicional é baseada nos princípios da aproximação do campo médio e da lei da ação das massas, os quais presumem que os indivíduos de uma espécie são ecologicamente equivalentes e suas interações são proporcionais às suas densidades. Esta abordagem tem se mostrado inadequada em descrever as dinâmicas do nicho trófico, visto que tanto fatores endógenos quanto exógenos contribuem de forma significativa para a variação do nicho populacional. Desse modo o presente estudo teve como objetivo investigar a dieta, a dinâmica do nicho trófico populacional do marsupial Gracilinanus microtarsus (Wagner, 1842) em uma área de cerradão em São Paulo, assim como investigar a influência da variação inter-individual neste fenômeno. A dieta de G. microtarsus foi composta de invertebrados e frutos, com a predominância de insetos. As amplitudes de nicho trófico de machos e fêmeas foram maiores na estação quente-úmida do que na fria-seca. Entre os sexos, a amplitude do nicho de machos e fêmeas aparentemente não diferiu na estação quente-úmida. Na estação fria-seca, fêmeas apresentaram nichos mais amplos do que os machos. No nível individual, os nichos tróficos de machos e fêmeas foram similarmente proporcionais ao nicho de sua população. No entanto, esta similaridade foi maior na estação fria-seca. Nem o tamanho amostral, nem o número de categorias alimentares detectadas nas fezes influenciaram estes resultados. Isto indica que, no geral, os indivíduos de G. microtarsus se comportam de forma oportunística, utilizando os recursos de acordo com sua disponibilidade no ambiente
Abstract: The niche theory occupies a central position in the Ecology, having a fundamental role in the population and community dynamic models. Despite this, its traditional formalization is based on the principles of the mean-field and on the law of mass action, which presume that the individuals of a species are ecologically equivalent and their interactions are proportional to their densities. This approach is inadequate in describing the dynamics of trophic niche, since many endogenous and exogenous factors contribute significantly to the variation of the population niche. This study aimed to investigate the diet, the dynamics of the population trophic niche of the gracile mouse opossum Gracilinanus microtarsus (Wagner, 1842) in a ¿cerradão¿ area of São Paulo state, as well as to investigate the influence of the inter-individual variation in this phenomenon. The diet of G. microtarsus was composed of invertebrates and fruits, with the predominance of insects. The trophic niche width of males and females was higher in the warm-wet season than in the cool-dry season. Between sexes, the niche width of males and females did not differ in the warm-wet season and in the cool-dry season. Females presented larger niche width than males. At the individual level, the niches of males and females were similarly proportional to their populations. However, in the cool-dry season, this similarity was higher. Neither amostral size nor number of food resource types detected in faeces influenced these results. This indicates that, in general, the individuals of G. microtarsus behave as opportunistic foragers, using the resources in according to with their availability in the environment
Mestrado
Mestre em Ecologia
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39

Tsujita, Maristela. "Participação do nicho endosteal na regulação da hemopoese de camundongos submetidos à desnutrição proteica." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/9/9136/tde-04052016-110647/.

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O nicho endosteal da medula óssea abriga as células-tronco hemopoéticas (CTH) em quiescência/autorrenovação. As CTH podem ser classificadas em dois grupos: células que reconstituem a hemopoese em longo prazo (LT-CTH) e curto prazo (CT-CTH). Investigamos, neste trabalho, os efeitos da desnutrição proteica (DP) no tecido ósseo e a participação do nicho endosteal na sinalização osteoblasto-CTH. Para tanto, utilizamos camundongos submetidos à DP induzida pelo consumo de ração hipoproteica. Os animais desnutridos apresentaram pancitopenia e diminuição nas concentrações de proteínas séricas e albumina. Quantificamos as CTH por citometria de fluxo e verificamos que os desnutridos apresentaram menor porcentagem de LT-CTH, CT-CTH e de progenitores multipotentes (PMP). Avaliamos a expressão das proteínas CD44, CXCR4, Tie-2 e Notch-1 nas LT-CTH. Observamos diminuição da expressão da proteína CD44 nos desnutridos. Isolamos as células LT-CTH por cell sorting e avaliamos a expressão gênica de CD44, CXCR4 e NOTCH-1. Verificamos que os desnutridos apresentaram menor expressão de CD44. Em relação ao ciclo celular, verificamos maior quantidade de LT-CTH nas fases G0/G1. Caracterizamos as alterações do tecido ósseo femoral, in vivo. Observamos diminuição da densidade mineral óssea e da densidade medular nos desnutridos. A desnutrição acarretou diminuição da área média das seções transversais, do perímetro do periósteo e do endósteo na cortical do fêmur dos animais. E na região trabecular, verificou-se diminuição da razão entre volume ósseo e volume da amostra e do número de trabéculas, aumento da distância entre as trabéculas e prevalência de trabéculas ósseas em formato cilíndrico. Avaliamos a expressão de colágeno, osteonectina (ON) e osteocalcina (OC) por imuno-histoquímica, e de osteopontina (OPN) por imunofluorescência no fêmur e verificamos diminuição da marcação para OPN, colágeno tipo I, OC e ON nos desnutridos. Evidenciamos, pela técnica do Picrosírius, desorganização na distribuição das fibras colágenas e presença de fibras tipo III nos fêmures dos desnutridos, além de maior número de osteoclastos evidenciados pela reação da fosfatase ácida tartarato resistente. Os osteoblastos da região femoral foram isolados por depleção imunomagnética, imunofenotipados por citometria de fluxo e cultivados em meio de indução osteogênica. Observamos menor positividade para fosfatase alcalina e vermelho de alizarina nas culturas dos osteoblastos dos desnutridos. Avaliamos, por Western Blotting, a expressão de colágeno tipo I, OPN, osterix, Runx2, RANKL e osteoprotegerina (OPG), e, por PCR em tempo real, a expressão de COL1A2, SP7, CXCL12, ANGPT1, SPP1, JAG2 e CDH2 nos osteoblastos isolados. Verificamos que a desnutrição acarretou diminuição da expressão proteica de osterix e OPG e menor expressão gênica de ANGPT1. Avaliamos a proliferação das células LSK (Lin-Sca1+c-Kit+) utilizando ensaio de CFSE (carboxifluoresceína succinimidil ester). Foi realizada cocultura de células LSK e osteoblastos (MC3T3-E1) na presença e ausência de anti-CD44. Após uma semana, verificamos menor proliferação das LSK dos desnutridos. O bloqueio de CD44 das LSK do grupo controle diminuiu a proliferação destas em três gerações. Entretanto, nos desnutridos, esse bloqueio não afetou a proliferação. Concluímos que a DP promoveu alterações no tecido ósseo e nas CTH. Entretanto, não podemos afirmar que as alterações observadas no sistema hemopoético foram decorrentes de alterações exclusivas do nicho endosteal.
The bone marrow endosteal niche hosts hematopoietic stem cells (HSC) in quiescence/self-renewal. HSC can be classified into two groups: cells capable of renewing indefinitely (LT-HSC) or repopulating in the short term (ST-HSC). In this work, we investigated the effects of protein malnutrition (PM) on bone tissue and the involvement of the endosteal niche in osteoblast-CTH signaling. Therefore, we used mice subjected to PM induced by the consumption of hypoproteic feed. Malnourished animals presented pancytopenia and decreased concentration of serum protein and albumin. We quantified the HSC by flow cytometry and found that the malnourished ones had lower percentage of LT-HSC, ST-HSC and multipotent progenitors (MPP). We assessed the expression of the CD44, CXCR4, Tie-2 and Notch-1 proteins in LT-HSC. We observed decreased expression of CD44 protein with the malnourished ones. We isolated the LT-HSC cells by means of cell sorting and assessed the gene expression of CD44, CXCR4 and NOTCH-1. We found that malnutrition had lower expression of CD44. Regarding the cell cycle, we see greater amount of LT-HSC in the G0 and G1 phases. We characterized the changes of the femoral bone tissue in vivo. We observed a decrease in the bone mineral density and medullar density in malnourished animals. As for malnourished animals, the femoral cortical region showed a significant decrease in tissue area, periosteal and endosteal perimeter. The femoral trabecular region of malnourished animals showed decreased bone volume/tissue volume ratio, decreased trabecular number, increased trabecular separation and prevalence of rod-like trabeculae. We investigated the expression of collagen, osteonectin (ON) and osteocalcin (OC) by means of immunohistochemistry and the expression of osteopontin (OPN) by immunofluorescence and we found that malnourished animals showed decreased labeling for OPN, type I collagen, OC and ON in the cortical region of the femur. Picrosirius staining was used to analyze disorganization of collagen fibers and presence of type III fibers in the femurs of the malnourished. Cortical and trabecular regions of malnourished animals presented a higher number of osteoclasts as shown by tartrate-resistant acid phosphatase reaction. Moreover, osteoblasts were isolated from the femoral region by immunomagnetic depletion and immunophenotyped by flow cytometry and cultured in osteogenic induction medium. Results proved less positive for alkaline phosphatase and alizarin red in the cultures of osteoblasts of malnourished animals. We assessed, by means of Western blotting, type I collagen expression, OPN, osterix, Runx2, RANKL and osteoprotegerin (OPG) and, by real time PCR, the expression of COL1A2, SP7, CXCL12, ANGPT1, SPP1, JAG2 and CDH2 with the isolated osteoblasts. We found that malnutrition led to osterix and OPG decreased protein expression and lower ANGPT1 gene expression. We evaluated LSK cell (Lin-Sca1+c-Kit+) proliferation by CFSE (carboxyfluorescein succinimidyl ester). LSK cells and osteoblasts (MC3T3-E1) cocultures were performed in the presence and absence of anti-CD44. After a week, we found lower proliferation of LSK in the malnourished. The LSK CD44 blocking in the control group decreased the proliferation of these three generations. However, as for the malnourished, such blockage did not affect proliferation. We concluded that the PM has promoted changes in bone tissue and the CTH. However, we can\'t claim that the alterations observed in hematopoietic system were due to endosteal niche-only changes.
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40

Alegria, João Pedro Duarte Nunes do Amaral. "Projeto aplicado de expansão de negócio de comercialização de biomassa." Master's thesis, Instituto Superior de Economia e Gestão, 2016. http://hdl.handle.net/10400.5/12405.

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Mestrado em Contabilidade, Fiscalidade e Finanças Empresariais
O presente projeto propõe a expansão de negócio da empresa Clean Forest, que se dedica sobretudo à comercialização de biomassa florestal, no sentido de a tornar mais competitiva tendo em conta o mercado onde opera. Para esse efeito prevê-se a introdução de um novo produto através de uma estratégia de diferenciação. Para a implementação da referida estratégia, será necessário uma série de alterações na atual estrutura da empresa, nomeadamente na sua imagem, nos mecanismos de comunicação com clientes, nos processos de produção, equipamentos e também modificações estruturais. Com efeito, para tal, o investimento a realizar é de cerca de 2.000.000 euros, sendo mais significativo o custo relacionado com a aquisição de novos equipamentos. O rigor e o detalhe técnico que presidiu à elaboração do presente projeto assente em investigação e na colaboração de diversos elementos, permite afirmar que se trata de um projeto de investimento viável. Todas as conclusões são suportadas por exercícios de resultados económico-financeiros, mesmo equacionando os cenários mais pessimistas.
This project proposes the expansion of Clean Forest, a company dedicated primarily to the sale of forest biomass. The main purpose is to transform Clean Forest into a competitive unit that deals with niche markets. To achieve this purpose, one of the main measures to be undertaken will be the introduction of a new product through a differentiation strategy. To implement the strategy, a series of changes in the current structure of the company will be required, particularly in its image, in the mechanisms of communication with customers, production processes, equipment and structural changes. For such changes, around 2.000.000 euros will be the minimum to invest, being more significant the cost related to the acquisition of new equipment. The accuracy and the technical detail that characterize the project based on research and collaboration of various elements, show that it is an acceptable one. Therefore, the credibility and viability are effective. All findings are supported by economic and financial results, even when equated the most pessimistic scenarios.
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41

Paula, Camilla de Souza. "Parti??o de recursos entre duas esp?cies simp?tricas de Gracilinanus (Didelphimorphia: Didelphidae) em uma ?rea de mata ciliar sav?nica: rela??o com o uso de ambiente e a dieta." UFVJM, 2017. http://acervo.ufvjm.edu.br/jspui/handle/1/1738.

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Na Capa, Folha de Rosto e Ficha Catalogr?fica constam o t?tulo: "Parti??o de recursos entre duas esp?cies simp?tricas de Gracilinanus (Didelphimorphia: Didelphidae): rela??o com o uso do espa?o e ecologia alimentar".
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Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM)
Diversas esp?cies de pequenos mam?feros Neotropicais ocorrem em simpatria ao longo de suas ?reas de distribui??o e ? relevante compreender os mecanismos que favorecem a coexist?ncia das esp?cies e que controlam a estrutura da comunidade ecol?gica. O objetivo do presente estudo foi analisar os poss?veis mecanismos de particionamento de recursos entre as esp?cies simp?tricas Gracilinanus agilise G. microtarsus, avaliando o nicho alimentar e o nicho espacial.O estudo foi realizado no per?odo de maio de 2016 a janeiro de 2017 em uma ?rea de mata ciliar sav?nica, no Parque Estadual do Rio Preto, Minas Gerais. Analisamos a dieta das duas esp?cies atrav?s da frequ?ncia de ocorr?ncia dos itens alimentares presentes nas fezes, al?m disso, estudamos o uso do espa?o realizado pelas esp?cies e a rela??o com a heterogeneidade e complexidade ambiental. Analisamos a dieta das duas esp?cies atrav?s da frequ?ncia de ocorr?ncia dos itens alimentares presentes nas fezes. As esp?cies apresentaram uma alta sobreposi??o de nicho no consumo de itens alimentares (CH=0,96), com algumas diferen?as na frequ?ncia de ocorr?ncia dos itens consumidos. Apesar dos itens mais frequentes nas amostras fazer parte da categoria dos invertebrados (Hymenoptera, Isoptera e Coleoptera), a propor??o que esses itens apareceram nas amostras foi diferente para as duas esp?cies, al?m disso, a variedade de itens alimentares tamb?m diferiu entre as esp?cies, onde observamos a presen?a de flores nas amostras de G. agilis, e uma maior variedade de frutos nas amostras de G. microtarsus. Atrav?s das abund?ncias relativas das esp?cies por estrato observamos que ambas utilizam preferencialmente o subbosque, al?m disso, observamos uma segrega??o espacial entre as esp?cies simp?tricas de Gracilinanus, com G. agilis aparentemente ocorrendo mais na borda da mata e, sua cong?nere G. microtarsus, mais no interior da mata. Apesar da alta sobreposi??o de nicho alimentar observada, os resultados indicam que a coexist?ncia das esp?cies simp?tricas estudadas pode estar associada a dois mecanismos: a flexibiliza??o no uso dos itens alimentares e particionamento no uso do espa?o.
Disserta??o (Mestrado) ? Programa de P?s-gradua??o em Biologia Animal, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017.
Several species of small Neotropical mammals occur in sympatry throughout their distribution areas and it is relevant to understand the mechanisms that favor the coexistence of the species and that control the structure of the ecological community. The objective of the present study was to analyze the possible mechanisms of partitioning of resources between the sympatric species Gracilinanus agilis and G. microtarsus, evaluating the food niche and the spatial niche. The study was carried out from May 2016 to January 2017 in an area of savanna ciliary forest, in the State Park of Rio Preto, Minas Gerais. We analyzed the diet of the two species through the frequency of occurrence of the food items present in their feces; in addition, we studied the use of the space realized by the species and the relation with the heterogeneity and environmental complexity. The species presented a high niche overlap in the consumption of food items (CH = 0.96), with some differences in the frequency of occurrence of the consumed items. Although the most frequent items in the samples belonged to the category of invertebrates (Hymenoptera, Isoptera and Coleoptera), the proportion that these items appeared in the samples was different for both species. The variety of food items also differed between the species, where the presence of flowers where more observed in the samples of G. agilis, and a greater variety of fruits was observed in the samples of G. microtarsus. The relative abundances of the species per stratum show that both species preferentially use the sub-forest, in addition, we observed a spatial segregation between the sympatric species of Gracilinanus, with G. agilis apparently occurring more at the edge of the forest, and its congener G. microtarsus further into the woods. Despite the high food niche overlap observed, the results indicate that the coexistence of the sympatric species studied may be associated to two mechanisms: flexibility in the use of food items and partitioning in the use of space.
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42

Andrade, Paula Cristina Barros. "Parti??o de recursos entre carn?voros simp?tricos (Didelphimorphia e Carn?vora) em um arroio de Mata Atl?ntica no sul do Brasil." UFVJM, 2017. http://acervo.ufvjm.edu.br/jspui/handle/1/1740.

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Funda??o de Amparo ? Pesquisa do estado de Minas Gerais (FAPEMIG)
Investigar as rela??es ecol?gicas entre esp?cies simp?tricas e suas intera??es com o habitat, s?o importantes para a compreens?o dos mecanismos que controlam a estrutura da comunidade ecol?gica. Entretanto, informa??es a respeito dos mecanismos que permitam a coexist?ncia entre mam?feros simp?tricos s?o ainda escassas. Descrevemos no presente estudo, os padr?es de dieta dos carn?voros simp?tricos Chironectes minimus e Lontra longicaudis, analisamos os poss?veis mecanismos de particionamento de recursos entre essas esp?cies, a partir das dimens?es de nicho alimentar, temporal e espacial e discutimos o potencial para intera??es interespec?ficas, como a competi??o e preda??o. Os h?bitos alimentares dos carn?voros foram estudados a partir das an?lises de amostras de fezes coletadas entre novembro de 2008 e fevereiro de 2012, em fragmentos de Mata Atl?ntica no arroio Morungava, localizado no munic?pio de Gravata?, Rio Grande do Sul, Brasil. Foram coletadas 85 amostras de C. minimus e 21 amostras de Lontra longicaudis, distribu?das entre 23 latrinas encontradas ao longo das margens direita e esquerda do arroio. A cu?ca d??gua e a lontra neotropical apresentaram h?bitos alimentares especialistas, por?m, com dietas distintas, especialmente com rela??o as preferencias alimentares e ? frequ?ncia dos itens consumidos, o que provavelmente se reflete no baixo ?ndice de sobreposi??o de nicho tr?fico entre as esp?cies. Chironectes minimus apresentou uma dieta primordialmente carnivora, no entanto, bastante diversificada, consumindo principalmente crust?ceos dec?podos (100%), insetos (69%) e peixes (40%), enquanto L. longicaudis apresentou uma dieta baseada principalmente no consumo de peixes (95%), seguidos por insetos (71%), e anf?bios anuros (67%). Observamos um padr?o de segrega??o espacial e temporal entre a cu?ca d??gua e a lontra neotropical na ?rea de estudo, embora, evid?ncias demonstrem que essas esp?cies coexistem em algum momento, tanto no espa?o quanto no tempo, j? que, registramos a preda??o da cu?ca d??gua pela lontra neotropical. Este ? o primeiro estudo de particionamento de recursos entre C. minimus e L. longicaudis, fornecendo informa??es importantes sobre os h?bitos alimentares destes mam?feros semiaqu?ticos e sobre os mecanismos ecol?gicos respons?veis pela estrutura desta guilda de carn?voros na Mata Atl?ntica.
Disserta??o (Mestrado) ? Programa de P?s-gradua??o em Biologia Animal, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017.
Investigate the ecological relationships between sympatric species and their interactions with the habitat are important for understanding the mechanisms that control the structure of ecological communities. However, informations regarding the mechanisms that allow the coexistence among sympatric mammals are still scarce. Here we described the feeding habits of two sympatric carnivores, Chironectes minimus and Lontra longicaudis, analyzed the resource partitioning mechanisms investigating different niche dimensions such as feeding, spatial and temporal niches, and also discussed the potential for interspecific interactions, such as intrespecific competition and predation. The feeding habits were studied from the analysis of fecal samples collected between November 2008 and February 2012, in fragments of Atlantic Forest in the Morungava stream, located in the city of Gravata?, Rio Grande do Sul, Brazil. 85 samples of C. minimus and 21 samples of Lontra longicaudis distributed among 23 latrines found along the right and left banks of the stream were collected, Water opossum and Neotropical otter presented specialized food habits, however, with different diets, especially regarding food preferences and frequency of consumed items, which is probably reflected by the slight trophic niche overlap between species. Chironectes minimus presented a primordial carnivorous diet, however, very diversified, consuming decapod crustaceans (100%), insects (69%) and fishes (40%), while L. longicaudis presented a diet based mainly on fish consumption 95%), followed by insects (71%), and anuran amphibians (67%). We observed a spatial and temporal segregation pattern among the water opossum and the Neotropical otter in the study site, although, evidences show that these species coexist at some time, both in space and time, since we recorded the predation of the water opossum by the Neotropical otter. This is the first study of resource partitioning among C. minimus and L. longicaudis, providing significant information about the feeding habits of these semi-aquatic mammals and about the ecological mechanisms responsible for the structure of this carnivorous guild in Atlantic Forest.
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43

Albuquerque, André Cardoso. "Germinação e estabelecimento inicial de espécies congêneres de ambiente seco." reponame:Repositório Institucional da UFC, 2015. http://www.repositorio.ufc.br/handle/riufc/17128.

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ALBUQUERQUE, André Cardoso. Germinação e estabelecimento inicial de espécies congêneres de ambiente seco. 2015. 34 f. Dissertação (Mestrado em ecologia e recursos naturais)- Universidade Federal do Ceará, Fortaleza-CE, 2015.
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In severe abiotic conditions, environmental filter selects phylogenetically related species. This trend promotes the problem of competitive exclusion, differentiation the regeneration niche for coexistence mechanism. There are studies of germination requirements and initial establishment of herbaceous species that indicate interspecific differences related to specialization pulse or interpulse, contributing to the coexistence in plant communities of arid and semi-arid environments. But there is a lack of studies seeking evidence for woody species. Seeking to fill the gap investigate differences in seed characteristics, germination and early development in two species of Mimosa. We found biometrics and water content in the seeds; germination under different temperatures; germination under different degrees of water stress; imbibition curve and initial development in lighting and irrigation treatments. Mimosa casealpiniifolia Benth. presented interpulse features on germination and early development, because of the higher seed size (larger amount of reserves); higher water content in the seed; Conservative soaking in water absorption curve; resistance to more intense water stress and better initial growth in water treatment interpulse than wrist. Mimosa tenuiflora Benth. showed characteristics of expertise to the wrists on germination and early development: small amount of reserves; low moisture content; rapid and greater water absorption in the imbibition curve; less resistance to water stress and better initial growth in pulse than interpulse. We conclude that the congeners studied tree species differ in the characteristics of seeds and germination; and have different initial responses and the development of treatments and interpulse pulse, so that indicates a performance difference in different moments of the water system; which can be related to the coexistence of these species.
Em condições abióticas severas, o filtro ambiental seleciona espécies filogeneticamente aparentadas. Essa tendência promove o problema de exclusão competitiva, sendo a diferenciação no nicho de regeneração um mecanismo para a coexistência. Existem estudos dos requerimentos de germinação e estabelecimento inicial de espécies herbáceas que indicam diferenças interespecíficas relacionadas à especialização a pulso ou interpulsos, contribuindo para a coexistência em comunidades vegetais de ambientes áridos e semiáridos. Porém existe uma falta de estudos buscando evidências para espécies lenhosas. Buscando preencher essa lacuna, investigamos diferenças em características de sementes, germinação e desenvolvimento inicial em duas espécies de Mimosa. Verificamos biometria e conteúdo de água nas sementes; germinação sob diferentes temperaturas; germinação sob diferentes graus de estresse hídrico; curva de embebição e desenvolvimento inicial sob tratamentos de luminosidade e irrigação. Mimosa casealpiniifolia Benth. apresentou características de interpulso na germinação e no desenvolvimento inicial, devido ao maior tamanho das sementes (maior quantidade de reservas); maior teor de água na semente; absorção conservadora de água na curva de embebição; resistência a estresse hídrico mais intenso e crescimento inicial melhor em tratamento hídrico de interpulso do que pulso. Mimosa tenuiflora Benth. apresentou características de especialização aos pulsos na germinação e no desenvolvimento inicial: pequena quantidade de reservas; baixo teor de umidade; rápida e maior absorção de água na curva de embebição; menor resistência ao estresse hídrico e crescimento inicial melhor em pulso do que interpulso. Concluímos que as espécies arbóreas congêneres estudadas divergem nas características das sementes e germinação; e apresentam respostas de desenvolvimento inicial distinta quanto aos tratamentos de pulso e interpulso, de forma que indica uma diferenciação de desempenho em diferentes momentos deste regime hídrico; que pode estar relacionada com a coexistência dessas espécies.
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44

Guo, Zhiqiang. "Séparation de niche entre deux espèces invasives de gobies." Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1842/.

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Comprendre la coexistence d'espèces et le maintien de la biodiversité est depuis longtemps un point central en écologie des communautés. La notion de niche, ou théorie des niches, a été largement développée depuis l'explication par Darwin de l'impressionnante diversité de la vie sur Terre. Celle-ci est considérée comme un mécanisme majeur permettant la coexistence d'espèces compétitrice au sein des communautés écologiques. La différenciation en niches spécifiques implique des différences spatiales, trophiques, temporelles et/ou une combinaison de celles-ci. Dans cette étude, la sélection d'habitat, les traits d'histoire de vie, la composition alimentaire et les comportements alimentaires de deux espèces invasives de gobiidés, très abondantes et écologiquement similaires (Rhinogobius cliffordpopei et Rhinogobius giurinus), sont comparées afin de tester si la séparation de niches est un mécanisme qui peut potentiellement permettre leur coexistence stable dans le lac Erhai (un lac superficiel d'eau douce du plateau de Yunnan-Guizhou en Chine). Les résultats montrent qu'il y a séparation des niches de ces deux espèces le long d'un axe d'habitat, d'un axe alimentaire (pour l'habitat littoral et pour les adultes et sub-adultes), et d'un axe temporel (en termes de cycles de ponte). Spécifiquement, R. Giurinus occupe principalement les habitats profonds (PH) alors que R. Cliffordpopei occupe principalement l'habitat littoral (LH). Des analyses corrélatives ont montré que l'abondance de R. Giurinus est positivement associée avec la profondeur de l'eau et les substrats composés de sables limoneux et grossiers, tandis que la distribution de R. Cliffordpopei est corrélée aux fortes densités en macrozooplankton, les fortes abondances en autres espèces de poissons, les fortes concentrations en oxygène dissout et les fortes densités en macrophytes submergées. Concernant le partage en ressources alimentaires, les deux espèces ont montré de clairs changements au niveau de leur diète ontogénique ainsi que dans les patrons de partage des aliments qui sont significativement différents selon le stade de leur histoire de vie et les habitats. Pour les deux espèces, les juvéniles consomment principalement du macrozooplancton (cladocères et copépodes), alors que les sub-adultes et les adultes consomment principalement des larves de Chironomidae et de Tubificidae. En LH, les sub-adultes et adultes des deux espèces présentent des différences significatives dans leur régime alimentaire alors que les juvéniles ont des régimes similaires. Cependant, en PH et SH, nous n'avons trouvé aucune preuve de partage des ressources alimentaires, quelque soit le stade de vie (juvéniles, sub-adultes et adultes). R. Cliffordpopei et R. Giurinus présentent un partage de leur niche temporel. En effet, les deux espèces ont des débuts de période de reproduction ainsi que des pics de reproduction à des moments différents. R. Cliffordpopei se reproduit de Février à Juin avec un pic de ponte entre Mars et Avril alors que l'activité de reproduction de R. Giurinus se fait entre Avril et Août avec un pic de ponte pendant les mois de Mai et Juin. Ces différences ont conduit à un partage temporel des cohortes de taille similaire entre les deux espèces, en particulier pour les larves de petite taille et les juvéniles, qui sont presque exclusivement zooplanctivores et qui exploitent les mêmes ressources alimentaires dans le lac. Cependant, l'activité nycthémérale (activité de locomotion) et le rythme d'alimentation varient légèrement entre les deux espèces, i. E. Les deux espèces présentent deux pics d'activités (6:00 - 10:00 et 18:00 - 22:00) et deux principales périodes d'alimentation (6:00 - 10:00 et 18:00 - 22:00) sur un laps de temps de 24h pour les quatre saisons. De plus, notre étude apporte une compréhension complète de la sélection d'habitat et des traits d'histoire de vie (i. E. Patron de croissance, biologie de la reproduction et dynamique de population) de ces deux espèces invasives de gobies. Ces résultats biologiques sont essentiels pour la mise en place de programmes économiquement et écologiquement efficaces de contrôle pour les deux espèces de ravageurs. De nouveau programmes de gestion sont fortement recommandés en vue de ces résultats. Par conséquent, dans cette étude, plusieurs programmes de restauration spécifiques et innovants sont proposés pour améliorer les stratégies actuelles de gestion dans une perspective de réduction des coûts et une meilleure efficacité
Understanding species coexistence and maintenance of biodiversity in nature has long been a central issue in community ecology. The niche or niche-based theory has been developed since Darwin's explanation of an amazing diversity of life on the Earth and considered as a major theory explaining the coexistence among competing species within ecological communities. Niche differentiation basically involves spatial, trophic, temporal and/or a combination of them. In the present study, habitat selections, life-history characteristics, diet compositions and feeding behaviors of two highly abundant and ecologically similar invasive goby species (Rhinogobius cliffordpopei and Rhinogobius giurinus) are compared to test whether niche separation is a potential mechanism allow ing the stable coexistence of them in Lake Erhai (a shallow freshwater lake in the Yunnan-Guizhou Plateau of China). The results demonstrated that these two species showed niche separation along habitat axis, food axis (in littoral habitat for sub-adults and adults), and temporal axis in terms of spawning cycles. Specifically, R. Giurinus mostly occupied profundal habitat (PH) while R. Cliffordpopei mainly used littoral habitat (LH). Correlation analyses revealed that the abundance of R. Giurinus was positively associated with deep water, silt and coarse sand substrata, whereas the distribution of R. Cliffordpopei was positively associated with high densities of macrozooplanktons and high abundances of other fish species, high concentration of dissolved oxygen and high densities of submerged macrophytes. For food resources partitioning, they showed a clear ontogenetic diet shifts and significantly different food partitioning patterns at different life-history stages and habitats. For both species, macrozooplanktons (Cladocera and Copepoda) were the main food for juveniles while sub-adults and adults primarily consumed Chironomidae larvae and Tubificidae. In LH, sub-adults and adults of the two species significantly differed in their diet compositions while juveniles showed similar diets. In PH and SH, however, there was no evidence for food partitioning between species at all the three life-history stages. R. Cliffordpopei and R. Giurinus showed temporal niche partitioning as they exhibited different onsets of spawning and peaks of spawning seasons, and thus different growth and population dynamics, though both of them are short-lived species with a life span of about one year. R. Cliffordpopei spawned from February to June with a spawning peak occurring in March and April. Spawning activity of R. Giurinus occurred from April to August with a peak activity during May and June. These differences resulted in a temporal partitioning for similar-sized cohorts, especially for small-sized larvae and juveniles, which were almost exclusively zooplanktivorous and exploited the same food resources in the lake. Moreover, their different spawning cycles led to different peak seasons for the highest population density of the two species. However, the diel activity (locomotory activity) and feeding rhythm varied slightly between them, i. E. Both species showed two peaks of activity (6:00 - 10:00 and 18:00 - 22:00) and two main feeding periods (6:00 - 10:00 and 18:00 - 22:00) in the four seasons. Moreover, our study provides a full understanding of habitat selection and life-history characteristics (i. E. Growth pattern, reproduction biology and population dynamic) of the two invasive gobies. These findings are crucial biological aspects for an economically and ecologically effective control programs to the two abundant pest species. The further management programs are highly recommended to give a careful consideration of these findings. Therefore, several specific remediation is suggested to improve the current management strategies from the perspective of cost-efficiency
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45

Purcell, Ceara K. Q. "How do Ecological Niches Evolve during Late Ordovician Environmental Change? A Test using Laurentian Brachiopods." Ohio University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1616426713257168.

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46

Pinto, Pedro Atã Ribeiro. "Niche builders: towards art as meta-semiotic engineering." Universidade Federal de Juiz de Fora, 2016. https://repositorio.ufjf.br/jspui/handle/ufjf/2232.

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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Este trabalho sugere uma estrutura teórica para uma Estética Cognitiva pragmaticamente orientada, baseada na Filosofia de Processos e Semiótica Cognitiva de Charles S. Peirce. Esta abordagem pouco explorada é capaz de fornecer novos métodos e premissas para a investigação da relação complexa entre obras de arte, significado, ambiente e artefatos, paradigmas artísticos, e criatividade. Nós oferecemos: (i) uma noção de criatividade artística relacionada as dinâmicas de construção de nicho cognitivo; (ii) um modelo da relação entre significado, criatividade, artefatos e nichos cognitivos; (iii) um modelo de construção de nicho cognitivo através de semiose icônica. As contribuições desta dissertação à Semiótica Cognitiva e Filosofia da Arte incluem, principalmente: a aproximação interdisciplinar entre conceitos e ferramentas teóricas oriundas da Filosofia de Processos, Semiótica, Solução Situada de Problemas, e Biologia Evolutiva; o fornecimento de uma série de análise de exemplos incluindo dança, literatura, música e tarefas de solução de problemas; a sugestação de uma estrutura conceitual para abordar fenômenos estéticos cognitivos.
This work suggests a framework for a pragmatist oriented Cognitive Aesthetics based on Peirce's Process Philosophy of Signs and Cognitive Semiotics. This little explored approach is capable of providing new methods and premises for investigating the complex relationship between artworks, meaning, environment, artistic paradigms, and creativity. We provide: (i) a notion of artistic creativity as related to cognitive niche construction dynamics; (ii) a model of the relationship between meaning, creativity, artifacts and cognitive niches; (iii) a model of cognitive niche construction through iconic semiosis. The contributions of this thesis to Cognitive Semiotics and Philosophy of Art include, mainly: the interdisciplinary approximation between concepts and theoretical tools from Process Philosophy, Semiotics, Situated Problem Solving and Evolutionary Biology; the provision of a series of example analysis in dance, literature, music and in problem solving tasks; the suggestion of a conceptual framework to approach cognitive aesthetic phenomena.
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47

Cuminetti, Vincent. "Etude de l'activité hématopoïétique du tissu adipeux chez la souris et l'homme." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30154/document.

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Le tissu adipeux (TA) contient un grand nombre de leucocytes qui jouent un rôle fondamental dans la régulation de l'activité métabolique du TA. Chez l'individu sain, les leucocytes du TA ont un profil majoritairement anti-inflammatoire (macrophages M2, polynucléaires éosinophiles, lymphocytes T CD4 Th2 et T régulateurs). Chez le sujet obèse, on observe une modification des populations immunitaires vers un phénotype majoritairement pro-inflammatoire (macrophages M1, polynucléaires neutrophiles, lymphocytes T CD8 et T CD4 Th1). Cet état inflammatoire participe au développement du syndrome métabolique. Chez l'adulte, les leucocytes circulants sont principalement produits dans la moelle osseuse (MO) par des cellules souches hématopoïétiques (CSH). Notre équipe a montré qu'une partie des leucocytes du TA sont produits in situ grâce à la présence de CSH tissulaires spécifiques, dont l'activité hématopoïétique diffère selon le dépôt adipeux. Ce résultat suggère que les CSH du TA pourraient être contrôlées par leur niche, comme c'est le cas dans la MO. Considérant le rôle prépondérant des leucocytes dans la physiopathologie du TA et le rôle des CSH dans ce tissu, les objectifs de cette thèse ont été les suivants : 1) Caractériser le rôle de l'hématopoïèse du TA dans le développement des maladies métaboliques. 2) Caractériser d'un point de vue cellulaire et moléculaire la niche des CSH du TA et la régulation de leur activité par cet environnement. 3) Mettre en évidence et caractériser l'activité hématopoïétique du TA chez l'homme. Concernant le premier objectif, nos résultats montrent que dans un modèle de diabète induit par un régime riche en gras, les CSH du TA produisent des macrophages pro- inflammatoires ayant un rôle direct dans le développement des altérations de l'homéostasie glucidique. La greffe de CSH du TA issues d'une souris diabétique dans une souris maintenue sous régime standard induit le transfert de la pathologie. Inversement, la greffe de CSH de TA d'une souris saine dans une souris diabétique améliore le phénotype métabolique. Concernant le second objectif, nous montrons que les CSH du TA se localisent préférentiellement dans le cœur du TA sous-cutané, région principalement composée d'adipocytes beiges, alors que la périphérie, constituée d'adipocytes blancs uniloculaires héberge moins de CSH. L'activation ou l'inhibition des adipocytes beiges diminue la quantité de CSH au cœur du tissu, montrant qu'un déséquilibre du métabolisme des adipocytes beiges a un impact sur les CSH, suggérant que ces adipocytes pourraient alors faire partie d'une niche hématopoïétique. Les approches in vitro ne nous ont pas permis d'aller plus loin dans la caractérisation des acteurs cellulaires et/ou moléculaires de cette niche. Concernant le troisième objectif, nous montrons pour la première fois la présence de CSH dans le TA chez l'homme. La fonctionnalité de ces CSH a été testée in vitro et in vivo. En culture en milieu semi-solide, les CSH de TA humain sont capables de donner des clones myéloïdes, comme chez la souris. In vivo, chez des souris immuno-déficientes reconstituées avec des CSH de TA humain, on retrouve des cellules immunitaires humaines dans le tissu adipeux, ce qui démontre leur capacité à reconstituer une partie du système immunitaire de ce tissu. En conclusion, ce travail de thèse a permis de montrer que l'activité hématopoïétique du TA joue un rôle crucial dans le maintien de la balance énergétique. Les CSH du TA résideraient préférentiellement dans une niche localisée au cœur du tissu, composée d'adipocytes beiges. La caractérisation des signaux moléculaires présents dans les différentes zones du TA permettra de proposer de nouvelles hypothèses sur la régulation de l'activité des CSH du TA. Chez l'homme, notre travail a permis de mettre en évidence une hématopoïèse tissulaire endogène au tissu adipeux, renforçant ainsi l'importance physiopathologique de nos précédents résultats obtenus chez la souris
The adipose tissue (AT) contains a lot of leukocytes that play a fundamental role in the regulation of AT metabolic activity. In a physiological situation, AT-leukocytes mostly display an anti-inflammatory profile (M2 macrophages, eosinophils, CD4 Th2 T cells and regulatory T cells). Obesity induces a shift in AT immune cells towards a pro-inflammatory phenotype (M1 macrophages, neutrophils, CD8 and CD4 Th1 T cells). This inflammatory state contributes to the development of the metabolic syndrome. In adults, circulating leukocytes are mostly produced in the bone marrow (BM) by hematopoietic stem cells (HSC). A few years ago, we have shown AT harbors a specific resident HSC population that can renew innate immune cells and especially macrophages in the AT, via in situ differentiation. This endogenous hematopoietic activity differs according to the localization of the fat pad, suggesting that like BM-HSC, AT HSC might be controlled by their environment. Considering the important role of leukocytes in the AT physiopathology and the role of resident HSC in this tissue, the objectives of this work were the followings: 1) To characterize the role of the AT hematopoiesis in the onset of metabolic diseases. 2) To characterize the AT HSC niche from a cellular and a molecular point of view, and the regulation of their activity by this environment. 3) To demonstrate the presence of an endogenous AT-hematopoiesis in humans. First, by using transplantation of sorted AT-HSC and gain and loss of function studies we showed that some of the inflammatory AT-macrophages inducing metabolic disease originate from resident AT-HSC. Transplantation of AT-HSC sorted from high fat diet-fed (HFD) mice is sufficient to induce AT-macrophage accumulation, and to transfer metabolic disease in control mice. Conversely, the transplantation of control AT-HSC improves both AT-inflammation and glucose homeostasis in HFD mice. Second, we showed that AT-HSC are preferentially localized in the core of sub-cutaneous AT that contains beige adipocytes, instead of the periphery that mostly harbors unilocular white adipocytes. Activation or inhibition of beige adipocytes induces a loss of this preferential localization, suggesting that modifications of the subcutaneous AT core region metabolism impact HSC behavior. This suggests that beige adipocytes might be a part of a hematopoietic niche in the AT. However, we were unable to characterize the cellular and/or molecular constituants of this niche. Finally, we showed for the first time that as in mice, human AT contains resident HSC. In methylcellulose semi-solid medium, human AT-HSC are able to produce myeloid clones. In vivo, after transplantation of human AT-HSC in immunodeficient mice, human immune cells are observed in the AT. These results show that human AT exhibit a functional endogenous hematopoietic activity. Altogether, we show in this study that the AT hematopoietic activity plays a crucial role in the control of energy balance. Although AT HSC are localized preferentially at the vicinity of beige adipocytes, molecular signals controlling this population remain to be characterized. Finally, we demonstrate for the first time an endogenous hematopoiesis in human AT, highlighting the physiopathological importance of our previous results obtained in mice
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48

Michel, Marcus. "Stem cell regulation in the Drosophila testicular niche." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-121226.

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All multicellular organisms constantly need to replace aged or damaged cells. This vital task of tissue homeostasis is fulfilled by stem cells. The balance between self-renewal and differentiation of the stem cell is crucial for this task and tightly regulated by a signaling microenvironment termed the niche. A widely used model for studying stem cell niche biology is the Drosophila testis, where two stem cell populations, the germline stem cells (GSCs) and the somatic cyst stem cells (CySCs), reside in a niche located at the apical tip. A lot is known about the signals regulating GSC maintenance in the testicular niche. It is, however, unknown how the spatial regulation of these signals defines the range of the niche. Here I show, that Bone Morphogenetic Protein (BMP) signaling is specifically activated at the interface of niche and stem cells. This local activation is achieved by coupling the transport of adhesion and signaling molecules in the niche cells and directing their transport to contact sites of niche and stem cells. Localized niche signaling at junctions underlies the so called stem-cell-niche synapse hypothesis proposed for the mammalian hematopoietic stem cell niche. I have shown that disrupting the localized transport causes premature differentiation and stem cell loss. BMP signaling between niche and GSCs therefore provides the first description of a stem-cell-niche synapse and will yield valuable insights into mammalian stem cell biology. The CySCs reside in the niche of the testis together with the GSCs. To understand how the niche maintains both stem cell types in a concerted way, it is essential to know the pathways regulating both stem cell types. Here I show that Hedgehog (Hh) signaling is a key stem cell factor of CySCs, while only indirectly affecting GSCs. Loss of Hh signaling in CySCs results in premature differentiation and consequent loss of the cells. Overactivation of the pathway leads to an increased proliferation and an expansion of the cyst stem cell compartment. As Hh signaling is also a regulator of the somatic cells in the mammalian testis and the Drosophila ovary this may reflect a higher degree of homology between these systems than previously expected.
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49

Fletcher, David. "Biological invasion risk assessment, considering adaptation at multiple scales : the case of topmouth gudgeon Pseudorasbora parva." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTG029/document.

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Afin de quantifier les risques d’invasion chez le goujon Asiatique Pseudorasbora parva, un petit cyprinidae d’eau douce, j’ai tout d’abord testé une approche corrélative de modélisation de la niche climatique dans laquelle j’ai intégré un proxy relatif à la probabilité d’introduction. Cette approche s’appuie sur des assomptions relatives à l’adaptation des organismes aux conditions environnementales locales ou régionales. J’ai ensuite comparé la niche climatique mesurée de deux lignées génétiques majeures à la fois dans les aires natives et envahies. Puis dans un second temps, par une approche expérimentale j’ai comparé la réponse aux variations de température, des traits d’histoire de vie de populations vivant dans des zones climatiques contrastées. Finalement, je me suis intéressé à la dispersion des goujons Asiatiques afin de mieux comprendre si les populations situées sur les fronts d’invasions avaient des capacités de colonisation plus importante. J’ai donc quantifié et comparé le long d’un gradient d’invasion, le potentiel de dispersion des individus ainsi que des traits pouvant y être liés (activité et morphologie). L’étude des risques d’invasions a montré que de nombreuses zones – au delà des zones déjà envahies - étaient climatiquement favorables au goujon Asiatique. C’était le cas en particulier pour certaines zones comme l’Australie, l’Amérique du Sud et du Nord, indiquant que l’invasion de cette espèce pourrait encore s’étendre. Après avoir pris en compte les probabilités d’introduction, cette étude a montré que l’Amérique du Nord était la zone la plus à risques. Par contre, la niche climatique entre les différentes lignées dans les zones géographiques envahies est très similaire, ce qui laisse à penser qu’il n’y a pas de patrons d’adaptation locale chez cette espèce. Pour autant, la niche climatique observée dans la zone envahie est très différente de celle observée dans la zone native, ce qui suggère un shift climatique important au cours de l’invasion. Les réponses thermiques des traits d’histoire de vie du goujon Asiatique testés expérimentalement n’ont pas varié significativement entre les populations originaires de conditions climatiques continentales et maritime-tempérées. Par exemple, l’effort reproductif global des femelles n’a pas varié entre les températures testées (15-25°C) mais la stratégie temporelle de reproduction a beaucoup varié. L’effort reproductif était plus cours et plus intense à forte température, alors qu’il était plus étalé et avec des pics reproductifs moins forts à faible température. Pour ailleurs, il semble qu’il existe un gradient morphologique fort entre les populations situées à différentes distances du front d’invasion ce qui suggère une forte plasticité morphologique mais qui ne serait pas liée à la capacité de dispersion de ces populations. En effet, cette dernière ne variant pas significativement le long du gradient d’invasion. La capacité de dispersion serait principalement liée à la taille du corps de goujon Asiatique, les individus les plus grands ayant une probabilité plus élevée de disperser.Bien que les prédictions générales du modèle de niche puissent être affectées par de potentielles adaptations à l’échelle de la population ou de la lignée évolutive, les résultats suggèrent qu’une certaine incertitude liée à ces prédictions persiste puisque la distribution native ne prédisait que très mal la distribution actuelle dans les zones envahies. Par ailleurs, mes travaux expérimentaux à plus fine échelle suggèrent que cette espèce est extrêmement adaptable et tolère une large gamme environnementale, ce qui pourrait expliquer son caractère invasif. Les connaissances produites au cours de cette thèse constituent donc des ressources extrêmement pertinentes pour développer des stratégies de gestion visant à contrôler les invasions futures du goujon Asiatique
In this thesis I set out to quantify the risk of invasion from the invasive freshwater fish, Pseudorasbora parva, at a global extent, using traditional correlative ecological niche modelling approaches with the integration of surrogate data representing introduction likelihood (Chapter I). These correlative approaches rely upon key assumptions relating to the presence or absence of local or regional adaptations, and so I subsequently tested for evidence of such adaptations in genetic lineages and in individual populations. This was achieved through analyzing climatic niche differentiation of key genetic lineages in the native and invasive ranges (Chapter II) and by conducting lab experiments comparing thermal responses of important life history traits in populations from contrasting climates (Chapter III). The initial risk assessment did not account for a key factor in invasions; namely, natural dispersal. Natural dispersal has been observed to be subject to selection in vanguard populations of invasive species, and adaptation of dispersal traits can infer additional invasive vigor, allowing the species to spread across the landscape quicker. For this reason, I quantified dispersal, activity and morphological differences, often associated with differential dispersal ability, in populations along a distance-gradient from an invasion front, in order to identify if P. parva is capable of such adaptations.The initial risk mapping study showed that large areas, beyond the current distribution of the species, are climatically suitable. These areas are mainly in North and South America, Australia and New Zealand, and constitute significant scope for spread and impact of this species. When introduction likelihood was included, N. America appears most at risk. I found no evidence to suggest that native genetic lineages represented local adaptations to their respective native climates - there was little or no differentiation of the lineages’ climatic niches in the invasive range. It was also apparent, from the niche comparisons, that the climatic niche in the invaded range constituted a significant shift, compared to the native range. The thermal responses of P. parva life history traits did not differ significantly between populations from a strongly seasonal continental climate and a mild temperate maritime climate. The overall reproductive output of females did not vary according to breeding season temperature, however, temporal reproductive strategy showed a strong response, with lower temperatures inducing a protracted breeding season and higher temperatures inducing rapid and intense reproductive output. The dispersal and morphology-related study identified a strong gradient of morphological change, corresponding with distance from invasion front. This demonstrates a high degree of plasticity in P. parva’s morphology in an invasion context, however this was not linked to either dispersal or activity levels, neither of which was significantly linked to distance from invasion front. Dispersal was best explained by body size, with larger fish more likely to disperse further.Whilst I found no evidence to suggest that the model predictions (Chapter I) were hampered by differentiation at either lineage or population levels, the findings of Chapter II do highlight the uncertainties surrounding the degree of conservatism in such predictions, mainly owing to the fact that past, native, distribution did not accurately predict the current invaded distribution. The results of Chapters II-IV show broad tolerances and great plasticity in P. parva, which likely underpin this species success as a pan-continental invader. The knowledge produced in this thesis provides a useful new resource for the development of management strategies for P. parva and could be usefully enhanced by the additional of analogous studies on native populations, which could help elucidate the source of the observed plasticity
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50

He, Liang. "Multiple Functions of Cables1 in Hematopoiesis." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS312.

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Abstract:
Cables1 est impliqué dans la régulation du cycle cellulaire et la survie. Par QPCR et western blot, Cables1 est fortement exprimé dans les cellules souches hématopoïétiques (CSH), les progéniteurs, les cellules de la niche médullaire et les mégakaryocytes. En utilisant un modèle de souris Cables1-/-, nous avons démontré que Cables1 est un régulateur clé de la maintenance homéostatique des CSH àl’état basal et sous stress hématopoïétique. Chez les souris jeunes dépourvues de Cables1, les progéniteurs hématopoïétiques sont hyperprolifératifs et ont un avantage compétitif de repeuplement. La surexpression lentivirale et la déplétion par shRNA de la protéine Cables1 ont respectivement entraîné une régulation positive et négative de p21, indiquant que l'effet de Cables1 sur la prolifération des progéniteurs est partiellement médiée par la régulation de p21. Avec l’âge, les souris déficientes en Cables1 présentent des anomalies du nombre de globules blancs accompagnées d'une réduction significative du compartiment CSH associée à une mobilisation accrue des progéniteurs. De plus, les souris Cables1-/-présentent une sensibilité accrue à un agent myélotoxique à l’irradiation due à des défauts dumicroenvironnement médullaire. Dans les mégacaryocytes, la diminution de Cables1 par shRNA entraîne un défaut de prolifération et unediminution du pourcentage de MK matures. De plus, un défaut de la capacité de formation de proplaquette a été observé après la diminution de Cables1. Ces effets peuvent s’expliquer par une apoptose accrue. En conclusion, Cables1 régule à la fois les progéniteurs et la mégacaryopoïèse. Cables1 donc est essentiel pour l'homéostasie des CSH et le contrôle du stress des CSH. La manipulation del’expression de Cables1 pourrait représenter une opportunité pour optimiser les schémas de chimiothérapie
Cables1 has been described to be involved in cell cycle regulation and survival. Using QPCR and western blot, we demonstrate for the first time that Cables1 in highly expressed in hematopoietic stem cells, in niche cells and megakaryocytes. Using the Cables1-/- mouse model, we demonstrate that Cables1 is a key regulator of homeostatic HSC maintenance and under hematopoietic stress. Young mice lacking Cables1 showed hyper proliferation within the hematopoietic progenitor and stem cell (HSPC) compartment. Loss ofCables1 conferred increased competitive repopulating capacity to the HSPCs. Lentiviral mediated overexpression and shRNA mediated depletion of Cables1 protein resulted in p21 up and down regulation, respectively, indicating that the effect of Cables1 on HSPC proliferation is partially mediated through regulating p21. By 1,5 to 2 years of age, Cables1 deficient mice displayed anomalies in whiteblood cell counts accompanied by a significant a reduction in the HSC compartment coupled with increased mobilization of HPC. In addition, Cables1-/- mice displayed increased sensitivity to myelotoxic agent and irradiation. These defects are related to abnormal microenvironment. We also investigated Cables1 function during megakaryopoiesis. Down regulation of Cables1 in CD41+CD42- megakaryocytic progenitors resulted in proliferative defect and decreased percentage of mature MKs, which were accompanied by p21(cyclin dependent kinase inhibitor) and Bax (an apoptosis related gene) up-regulation. Moreover, defect of proplatelet forming capacity was observed after Cables1 knockdown, which can also be explained by elevated apoptosis induced by Bax protein. In conclusion, Cables1 regulate both HSPCs and the process of megakaryopoiesis. It represents a opportunities to optimize chemotherapy schemes
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