To see the other types of publications on this topic, follow the link: Dispersal.
Dissertations / Theses on the topic 'Dispersal'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Dispersal.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Lou, Vega Salvador 1972. "Modelo matemático para o estudo do efeito Allee sobre a dispersão de plantas por agentes e em meios heterogêneos." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/306712.
Full textAbstract:
Orientador: Wilson Castro Ferreira JuniorTese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica
Made available in DSpace on 2018-08-22T04:48:33Z (GMT). No. of bitstreams: 1 LouVega_Salvador_D.pdf: 14692586 bytes, checksum: f745ca7fb3da3cfa09dfb8a8dd9f37bb (MD5) Previous issue date: 2013
Resumo: Apresentamos um modelo integro - recursivo para a dispersão de uma planta que acopla uma dinâmica de reprodução, com efeito, Allee e uma dinâmica de dispersão em um meio heterogêneo. Propomos um modelo de difusão e sedimentação para derivar núcleos de dispersão teóricos, que representem o padrão de dispersão de sementes gerado por pássaros frugívoros em um meio heterogêneo. O núcleo gerado através do modelo _e capaz de reproduzir o padrão espacial de agregação de sementes gerado pelos pássaros frugívoros sob condições naturais. Enquanto _a dinâmica de reprodução, consideramos um efeito Allee devido à limitação de pólen, que reduz a produção de sementes. Introduzimos o efeito Allee através de uma função de probabilidade que depende da densidade local de plantas. Analisa-se o comportamento da expansão da planta, e estima-se a velocidade média de expansão. O modelo mostra uma invasão através de pulsos, que atribuímos ao efeito Allee e ao comportamento de dispersão da planta
Abstract: We present an integro-difference model for a plant dispersal, which couples a reproductive dynamic with Allee effect and dispersal dynamic in a heterogeneous environment. We propose diffusion and settling model to derive theoretical dispersal kernels that represent the seed dispersal pattern generated by frugivores birds in a heterogeneous environment. The dispersal kernel derived through the model is able to reproduce the aggregate seed dispersal pattern generated by the frugivores birds under field conditions. As for the reproductive dynamic, we consider an Allee effect due to pollen limitation, which reduces seed production. We introduce the Allee effect through a probability function, which depends on the local plant density. The plant expansion behavior is analyzed, and the average expansion speed is estimated. The model shows a pulsed invasion, which we attribute to the Allee effect and the plant dispersal behavior
Doutorado
Matematica Aplicada
Doutor em Matemática Aplicada
2
Newell, Simon C. "Dispersal in carabids." Thesis, University of Plymouth, 1986. http://hdl.handle.net/10026.1/2725.
Full textAbstract:
The study consisted primarily of a number of surveys in brassica fields, using pitfall and gutter traps. At all sites a number of different species of carabids were marked and released. From the pitfall trapping it was found that different carabid species inhabitated different parts of the field, particularly in relation to the field boundaries. Two common species, Nebria brevicollis and Bembidion lampros, over-wintered in the hedgebanks, moving out into the fields in the spring. Two other common species, Pterostichus melanarius and Harpalus rufipes, were primarily associated with the field, but activity in the field boundaries continued later into the year. Marking concentrated on four species; P. cupreus, P. melanarius, H. rufipes and N. brevicollis. At all sites the recapture rate of rufipes was much lower than that of P. melanarius, though they are of similar size. Using this data, mean displacement/day was calculated for each species. To identify the causes for the differences in recapture rate between the species, two species were individually tracked at night, in the field. Positions every two minutes were recorded and the distance and turn between each point measured. The results showed that H. rufipes had a higher turn rate and moved less than melanarius. The data from tracking was incorporated into a computer simulation model which recreated the beetles' tracks, using the same time interval. Traps were added and the model used to simulate the recapture experiments in the field. Changes in dispersal patterns were used to create differences in the catch in different patches. It was found that changes in turning behaviour could not produce changes in density, because of behaviour at the boundaries. Delaying the change in behaviour produces differences in numbers, but orientation is the most likely mechanism. The relationship between step length, turn and catch was also evaluated.
3
Heinz, Simone K. "Dispersal in fragmented landscapes : from individual dispersal behaviour to metapopulation dynamics /." Leipzig-Halle : UFZ-Umweltforschungszentrum Leipzig-Halle, 2004. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015383379&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Full text
4
Ansong, Michael. "Unintentional Human Dispersal of Weed Seed." Thesis, Griffith University, 2016. http://hdl.handle.net/10072/365736.
Full textAbstract:
Seed dispersal is an important biological process as propagule pressure affects the success of plant invasions. The role and importance of humans in this process is increasingly recognised, particularly in relation to long distance seed dispersal. There is still comparatively limited research on unintentional human-mediated seed dispersal, including for seed dispersed from clothing, compared to other dispersal mechanisms such as wind or seed attached to fur. With more people travelling globally, including to remote locations, humans can unintentionally transport seeds over long distances. This can facilitate biological invasions in urban, rural and remote natural areas when it involves the dispersal of weed seed.
Weeds, which are often defined as plants growing in sites where they are not wanted, are a major problem in both natural and agricultural systems. They can reduce biodiversity in natural ecosystems and productivity in agricultural regions, and once established, they are expensive to control or eradicate. Therefore, limiting weed seed dispersal, including over long distances, is important in controlling their spread globally. This thesis examines aspects of unintentional human-mediated weed seed dispersal, using data mining, experimental, modelling and social methods.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text
5
Meister, Gerald Alan. "Dispersal of transposable elements." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0019/NQ46389.pdf.
Full text
6
Clarke, S. A. "Dispersal of Satyrid butterflies." Thesis, Oxford Brookes University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383645.
Full text
7
Paulson, Matthew David. "Seasonal dispersal of pests." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529837.
Full text
8
Bonadonna, Costanza. "Models of tephra dispersal." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367665.
Full text
9
Lou, Vega Salvador 1972. "Dispersão de longo alcance e efeito Allee em um processo invasivo." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/306718.
Full textAbstract:
Orientador: Wilson Castro Ferreira JuniorDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica
Made available in DSpace on 2018-08-12T08:00:18Z (GMT). No. of bitstreams: 1 LouVega_Salvador_M.pdf: 1338284 bytes, checksum: f247d3dc13a783da27d224a3d32df47b (MD5) Previous issue date: 2008
Resumo: Proponemos um modelo matemático para uma planta invasora, que acopla a dinâmica de reproduão com Efeito Allee e a dispersão de longa distância de uma planta invasora. Consideramos um efeito Allee devido à limitação de pólen, que reduz a produção de sementes. Introduzimos o efeito Allee através de uma função de probabilidade de encontro pólen-estigma que depende da densidade de plantas. Para a modelagem do processo de dispersão utilizamos equações íntegrorecursiva (IRE) tomando um núcleo de dispersão misto, que representa a dispesão local e a longa distância. Analisamos a dinâmica local do modelo determinando os pontos de equilíbrio e as suas estabilidades, para então analisar o processo de dispersão. Analisamos o modelo de dispersão por meio de simulação numérica, o que permitiu observar o deslocamento espacial da frente da invasão. Isto permitiu calcular a velocidade de expansão. Determinamos a inuência do efeito Allee, da capacidade reprodutiva e da dispersão de longa distância sobre a velocidade de expansão. Observamos que o efeito Allee torna velocidades aceleradas em velocidades constantes de expansão. A velocidade de expansão decresce com o aumento na intensidade do efeito Allee, mas aumenta com a capacidade reprodutiva. A dispersão de longa distância gera maiores velocidades de expansão, embora para fortes intensidades do efeito Allee o acréscimo na velocidade não é signifícativo em relação à velocidade gerada pela dispersão local. Os resultados mostram que apesar da dispersão contribuir ao aumento na velocidade de expansão, a dispersão também torna a população mais suscetável á extinção.
Abstract: We present a mathematical model which couples the reproductive dynamic with an Allee effect and a long distance diseprsal of an invasive plant. We consider an Allee effect due to pollen limitation, which reduces seed production. We introduce the Allee effect through a probability function that describes pollen-stigma encounters as function of the population density. To model the dispersal process we used integro-diference equations (IDE) and employed a mixed kernel which represents the local and long distance dispersal processes. We analyzed the local dynamic through the stability of their equilibrium points. For the spatial dynamic we used numerical simulations, that allowed us to observe the spatial displacement of the invasion front. This permitted us to compute the expansion speeds. We determined the inuence of the Allee effect, reproductive capacity and the long distance diseprsal on the invasion speeds. We observed than an Allee effect turns accelerating expansion speeds into constant speeds. Expansion speeds decreases with Allee effect intensity but increases with the reproductive capacity of the population. Long distance dispersal produces higher invasion speeds, but for strong intensities of the Allee effect, the increase is not significant in relation to the speeds generated by the local dispersal. Our results show that while dispersal contributes to expansion speeds, it also turns the population more susceptible to extinction.
Mestrado
Biomatematica
Mestre em Matemática Aplicada
10
Gwynne-Evans, David. "The dispersal paradox : can lowland granivorous mice also disperse the seeds they devour?" Bachelor's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/24830.
Full textAbstract:
The relationship between two rodent species and the Cape Reed (Willdenowia incurvata) were examined. Many studies have focussed on the role of rodents as predators of plant seeds. However, it seems that certain rodents may actually perform a crucial role in the dispersal of plants. Experiments to uncover the dispersal mechanism were carried out. Also examined is the role of the appendages present on the Restio seeds, possibly as energy-rich rewards for dispersal for the rodents. It was found that the Restio may be dependent on seed-dispersing rodents, although this mutualism is not so important in fragmented habitats.
11
KHALIQ, ALI ABDUL. "Gas Dispersal Simulation in ROS." Thesis, Örebro universitet, Akademin för naturvetenskap och teknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-20431.
Full textAbstract:
This work presents a 3-D gas dispersal simulation and olfactory detection system implemented in ROS. Gas dispersal simulation integrates OpenFOAMflow simulation and a filament-based gas propagation model to simulate gas dispersion for compressible flows with a realistic turbulence model. The olfactory detection system models the response of metal oxide gas sensor to the simulated gas. Olfaction related experiments in mobile robots can be highly complex and hazardous due to the involvement of flammable and toxic gases. Moreover, the results of mobile olfaction task depends on the characteristics of environment and on the characteristics of odor detection system. The precision of results of this task is usually effected due to the variability of interrelationships between these characteristics which can create complications to focus on task aspect. The motivation behind the development of this simulation package is to make environment and odor detection system controllable, where experiments can be repeated under identical conditions, bypassing the environmental hazards so that the research work can concentrate on task aspect. The simulation package is validated through the results obtained by various tests including constant concentrations in ideal conditions as well as changing concentration in turbulent environment. i
12
Owen, James Edward. "Protoplanetary disc evolution and dispersal." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/240630.
Full textAbstract:
In this thesis I have studied how discs around young stars evolve and disperse. In particular, I build models which combine viscous evolution with photoevaporation, as previous work suggests that photoevaporation can reproduce the observed disc evolution and dispersal time-scales. The main question this thesis attempts to address is: Can photoevaporation provide a dominant dispersal mechanism for the observed population of young stars? Photoevaporation arises from the heating that high energy (UV and X-ray) photons provide to the surface layers of a disc. Before I started this work, only photoevaporation from a pure EUV radiation field was described within a hydrodynamic framework. Therefore, I start by building a hydrodynamic solution to the pure X-ray photoevaporation problem, and then extend this solution to the entire high energy spectrum. This hydrodynamic model leads me to conclude that it is the X-ray radiation field that sets the mass-loss rates. These mass-loss rates scale linearly with X-ray luminosity, are independent of the underlying disc structure and explicitly independent of stellar mass. I build a radiation-hydrodynamic algorithm, based on previous work, to describe the process of X-ray heating in discs. I then use this algorithm to span the full range of observed parameter space, to fully solve the X-ray photoevaporation problem. I further extend the algorithm to roughly approximate the heating an FUV radiation field would have on the photoevaporative flow, as well as separately testing the effect an EUV radiation field will have. These numerical tests are in agreement with the hydrodynamic model derived. Specifically, it is the X-rays that are driving the photoevaporative flow from the inner disc. Armed with an accurate description of the photoevaporative mass-loss rates from young stars, I consider the evolution of a population of disc-bearing, young (
13
Maio, Gianluca Faculty of Science UNSW. "Asymmetrical dispersal in simulation analysis." Publisher:University of New South Wales, 2008. http://handle.unsw.edu.au/1959.4/43382.
Full textAbstract:
Asymmetrical dispersal is when dispersal rates differ in opposite directions. This is expected to be common in natural populations. This work aims to study the symmetrical and asymmetrical dispersal through the use of a simulation program, simuPOP. The main questions were (i) "what are the differences between asymmetrical and symmetrical dispersal in relation to genetic differentiation and equilibrium?" and (ii) "Is it possible to identify asymmetrical dispersal structure from observed patterns of genetic differentiation between populations, and variation within populations?". To address these questions, simulations were conducted with two and three subpopulations subject by three different dispersal rate contrasts and several spatial patterns of dispersal. Variables were estimated at drift-dispersal equilibrium included genetic differentiation between subpopulations (θ) and heterozygosity. With pairwise θ for three subpopulations it was possible to determine whether the metapopulations were subject to symmetrical or asymmetrical dispersal and sometimes to identify the structure of dispersal. Equilibrium heterozygosities did not aid diagnosis of asymmetrical dispersal patterns. I also checked the applicability of two predictions originally made for symmetrical dispersal: Wright's expectations for θ at equilibrium, and Whitlock's expectations fro time to half of equilibrium θ. In most cases these expectations were not applicable. Study of asymmetrical dispersal on living organisms is strongly encouraged.
14
Hodkinson, Dunmail John. "Plant dispersal : vectors and tradeoffs." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389924.
Full text
15
Lönnell, Niklas. "Dispersal of bryophytes across landscapes." Doctoral thesis, Stockholms universitet, Institutionen för ekologi, miljö och botanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-100064.
Full textAbstract:
Dispersal, especially long-distance dispersal, is an important component in many disciplines within biology. Many species are passively dispersed by wind, not least spore-dispersed organisms. In this thesis I investigated the dispersal capacity of bryophytes by studying the colonization patterns from local scales (100 m) to landscape scales (20 km). The dispersal distances were measured from a known source (up to 600 m away) or inferred from a connectivity measure (1–20 km). I introduced acidic clay to measure the colonization rates over one season of a pioneer moss, Discelium nudum (I–III). I also investigated which vascular plants and bryophytes that had colonized limed mires approximately 20–30 years after the first disturbance (IV). Discelium effectively colonized new disturbed substrates over one season. Most spores were deposited up to 50 meters from a source but the relationship between local colonization rates and connectivity increased with distance up to 20 km (I–III). Also calcicolous wetland bryophyte species were good colonizers over similar distances, while vascular plants in the same environment colonized less frequently. Common bryophytes that produce spores frequently were more effective colonizers, while no effect of spore size was detected (IV). A mechanistic model that take into account meteorological parameters to simulate the trajectories for spores of Discelium nudum fitted rather well to the observed colonization pattern, especially if spore release thresholds in wind variation and humidity were accounted for (III). This thesis conclude that bryophytes in open habitats can disperse effectively across landscapes given that the regional spore source is large enough (i.e. are common in the region and produce spores abundantly). For spore-dispersed organisms in open landscapes I suggest that it is often the colonization phase and not the transport that is the main bottle-neck for maintaining populations across landscapes.At the time of the doctoral defence the following papesr were unpublished and had a status as follows: Paper 2: Epubl ahead of print; Paper 3: Manuscript; Paper 4: Manuscript
16
Jardini, Michael Anthony. "Methodologies for Investigating Cultivar Dispersal." Thesis, The University of Arizona, 2014. http://hdl.handle.net/10150/555543.
Full textAbstract:
Cultivar dispersal is related to food choice by the scale of the event: food choice occurs at an individual level, while dispersal occurs at a societal level. Dispersal is investigated by using data from the FAO, specifically the FAOSTAT tool and the GAEZ database, and literature review. A number of methodologies are tested in order to determine the best method for investigating dispersal; methodologies include visal comparison, normalization and statistical analysis of production and consumption values, measures of crop suitability, and investigation of botanical origin. Quantitative analysis is found to be satisfying, while qualitative analyses are found to require more data and investigation. Cultivars are found to be either dispersed globally or localized, with few cultivars in between.
17
Byrne, David N., and David E. Bellamy. "Predicting Dispersal by Whitefly Parasitoids." College of Agriculture, University of Arizona (Tucson, AZ), 2000. http://hdl.handle.net/10150/220016.
Full textAbstract:
These experiments were designed to examine short-range dispersal by the small whitefly parasitoid Eretmocerus eremicus that takes place within the confines of a specifically defined habitat. We were specifically concerned with the impacts of sex and mating status on their dispersal. We hoped to construct predictive models concerning dispersal. In a vertical flight chamber we found that female flight duration was significantly longer (11 times) than that of males and that unmated parasitoids flew approximately three times longer than mated individuals. In field studies 87% of the 4,153 parasitoids captured were males. This occurred in spite of sex ratios being near 1:1 upon release. The difference in dispersal characteristics between males and females may be resource based. It is felt that certain requirements were met within our field plots for males that were not met for females. It is important for males to find mates and they may have done so inside release containers or in close proximity to release sites. While females have a similar requirement, they must also find whitefly hosts to parasitize. It can be assumed that each sex took active steps to accomplish different goals. Males were searching the immediate area of the release sites where mates were plentiful, while females were leaving the 33 ft. radius plots in search of whitefly hosts. We were able to verify models for male dispersal (75% of males were predicted to disperse within 13.5 ft.). Our models predicted that 50% of females would be found within 82 ft. This information will useful when describing movement by E. eremicus and other small insects. It should prove useful when defining release techniques for parasitoids being used as biological control agents.
18
Bigsby, Kevin M. "Anthropogenic Drivers of Gypsy Moth Dispersal." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-03202009-173827/.
Full textAbstract:
Gypsy moth (Lymantria dispar: Linnaeus) is a polyphagous non-native forest pest first introduced to Medford, Massachusetts in 1869. It has since spread as far south as North Carolina and as far west as Wisconsin. Gypsy moth is responsible for defoliating approximately 100,000 hectares of forest annually, resulting in mortality in a small percentage of trees, averting behavior by recreators, and creating a nuisance to the general public. Limiting the spread of gypsy moth is beneficial because it delays the onset of costs and losses associated with quarantine, tree defoliation and mortality, and nuisance. Gypsy moth is believed to disperse naturally up to 2.5 km/yr (e.g. early instar ballooning) but has been observed to disperse much greater distances. The scientific consensus is that this longer distance dispersal occurs through anthropogenic vectors (e.g. egg masses being transported on firewood). Despite the resources that United States Department of Agriculture and state agencies dedicate to eliminating and managing new infestations resulting from long distance dispersal, there has been limited empirical research on the relationship between the dispersal of gypsy moth and the movement of people and their goods. This thesis develops a conceptual framework of the anthropogenic factors that could affect dispersal, measures these factors with secondary data at the county level from a variety of sources, and estimates the presence or absence of gypsy moth using logistic regression models. The dependent variable is drawn from trap catch records archived by the United States Department of Agriculture Forest Service program, Slow-the-Spread, in areas distal to the 1 moth/trap line between 1999 and 2007. Through step-wise logistic regression estimating sub-models that include variables representing each broad anthropogenic factor, a final empirical model is specified. The variables of the model are estimated independently for each year from 1999 to 2007, resulting in a mean Pseudo R square of 0.568. Consistently significant ( ) anthropogenic variables are the number of households using wood for heating fuel and mean household income. These findings are discussed with regard to invasion theory and quarantine policy. One key implication is the continual importance of regulating and raising awareness about the risk of moving firewood from infested to uninfested zones.
19
Clark, Craig Andrew. "Numerical simulations of maize pollen dispersal." [Ames, Iowa : Iowa State University], 2007.
Find full text
20
Mashanova, Alla. "Measuring and modelling individual dispersal behaviour." Thesis, Royal Holloway, University of London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521750.
Full text
21
Rosotti, Giovanni. "Proto-planetary disc evolution and dispersal." Diss., Ludwig-Maximilians-Universität München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:19-182903.
Full text
22
Alemadi, Shireen. "DISPERSAL BEHAVIOR OF MOSQUITOFISH (GAMBUSIA HOLBROOKI)." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2910.
Full textAbstract:
Mosquitofish (Gambusia holbrooki) are native to the southeastern United States but invasive elsewhere, and are dominant predators in many ecosystems that they inhabit. Information on dispersal behavior will help better understand and predict mosquitofish metapopulation dynamics and invasions. I experimentally tested dispersal behavior of individual mosquitofish under a range of laboratory conditions relevant to field situations. Preliminary experiments showed that gender, lighting conditions, hunger and acclimation time did not significantly affect net dispersal rate. Power analysis based on this preliminary experiment determined that 6 replicate fish were sufficient for each subsequent experiment; I used 24 fish, and each fish was tested one time. Three factors that potentially could affect net swimming rate were tested: habitat of origin (permanent vs. temporary waters), water depth (3-24 mm), and the interaction between water depth and leaf litter type (upland and wetland). Fish from a temporary pond dispersed significantly faster than fish from a permanent pond, and fish dispersed significantly faster in deeper water than in shallower water. However, leaf litter significantly inhibited fish dispersal at all depths tested. Based on these experiments, G. holbrooki disperse more readily through relatively open and deeper (several centimeters) pathways between habitats such as roadside ditches, drainage canals and trails in flooded conditions. My results are useful for understanding mosquitofish dispersal behavior based on the abiotic and biotic factors examined in this experiment. I predict that mosquitofish can spread from a point of introduction at about 800 m per day, given and unobstructed path of only > 6 mm depth.M.S.
Department of Biology
Arts and Sciences
Biology
23
Fowler, Michael S. "Interactions between density dependence and dispersal." Thesis, University of Glasgow, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248291.
Full text
24
Simmons, Adam David. "Changes in dispersal during range expansion." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396933.
Full text
25
Williams, Roger Haydn. "Dispersal of the mycoparasite Coniothyrium minitans." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242306.
Full text
26
Hobson, L. "Dispersal and reproductive competition in mammals." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3005820/.
Full text
27
Kim, Stacy L. "Larval dispersal between hydrothermal vent habitats." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/40566.
Full text
28
Shaw, Emma McCarroll. "Agricultural spiders : distribution, dispersal and behaviour." Thesis, Manchester Metropolitan University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405982.
Full text
29
Noble, Laine. "Evolution of Dispersal in Patchy Habitats." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1448878039.
Full text
30
Jones, Hayley B. C. "Quantifying dispersal in British noctuid moths." Thesis, University of York, 2014. http://etheses.whiterose.ac.uk/8597/.
Full textAbstract:
Dispersal is an important process in the ecology and evolution of organisms, affecting species’ population dynamics, gene flow, and range size. Around two thirds of common and widespread British macro-moths have declined in abundance over the last 40 years, and dispersal ability may be important in determining whether or not species persist in this changing environment. However, knowledge of dispersal ability in macro-moths is lacking because dispersal is difficult to measure directly in nocturnal flying insects. This thesis investigated the dispersal abilities of British noctuid moths to examine how dispersal ability is related to adult flight morphology and species’ population trends. Noctuid moths are an important taxon to study because of their role in many ecosystem processes (e.g. as pollinators, pests and prey), hence their focus in this study. I developed a novel tethered flight mill technique to quantify the dispersal ability of a range of British noctuid moths (size range 12 – 27 mm forewing length). I demonstrated that this technique provided measures of flight performance in the lab (measures of flight speed and distance flown overnight) that reflected species’ dispersal abilities reported in the wild. I revealed that adult forewing length was a good predictor of inter-specific differences in flight performance among 32 noctuid moth species. I also found high levels of intra-specific variation in flight performance, and both adult flight morphology and resource-related variables (amount of food consumed by individuals prior to flight, mass loss by adults during flight) contributed to this variation. Analysis of Rothamsted Insect Survey data and National Moth Recording Scheme data of changes in moth abundance and distribution patterns in the UK over the past 4 decades provided some evidence that dispersal ability (measures of adult forewing length) contributed to species’ population trends. The analysis indicated that species with intermediate dispersal ability may be declining more than those of either high or low dispersal ability. I conclude that the new tethered flight technique demonstrated in this thesis provides opportunities for multi-species and cross-taxon comparisons of dispersal ability. The utility of wing length as a proxy for dispersal ability may facilitate the inclusion of dispersal information into analyses for a wide range of insects. Dispersal has some effect on moth distribution and abundance changes but other factors such as habitat availability and responses to changing climate are likely to play a role.
31
Naylor, Richard A. "Ecology and dispersal of the bedbug." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/2244/.
Full textAbstract:
The global bedbug resurgence has left the scientific community racing to fill large gaps in our understanding of the biology and ecology of this forgotten pest. Studying the ecology of a species so closely associated with humans has inherent difficulties, necessitating the development of laboratory arenas that replicate natural infestations. The arena developed herein provides bedbugs with the opportunity to exhibit natural foraging, hiding and dispersal behaviours on a scale that reflects their natural environment. Using this arena I test hypotheses relating to; 1) how bedbugs use harbourage space, and 2) the factors affect their dispersal. My research revealed that harbourages in the vicinity of the host are used first and peripheral harbourages only form as the infestation develops. The preferential use of harbourages adjacent to the host is explained by the finding that feeding frequency was negatively correlated with distance from the host. However, despite this advantage of residing in close proximity to the host, bedbugs form discontinuous harbourages, leaving regions of unoccupied space. This suggests that there are factor(s) that limit harbourage density. Female dispersal was unaffected by males presence, suggesting that sexual harassment does not drive dispersal in the bedbug. However, variation in the distribution of the sexes across harbourages suggests that females may be able to avoid males through harbourage selection. Increased harbourage availability significantly delayed the onset of dispersal, suggesting that competition for harbourages near the host is a factor driving dispersal from the natal infestation. Given that a host is an almost unlimited food source and that the cost of dispersing is likely to be high, it is not immediately apparent why bedbugs choose to actively disperse. However, theoretical models show that where relatedness is high, dispersal always occurs to reduce competition. The high cost of dispersal may therefore be offset by kin selection.
32
Banha, Filipe Miguel Santos. "Human dispersal of freshwater invasive fauna." Doctoral thesis, Universidade de Évora, 2016. http://hdl.handle.net/10174/18152.
Full textAbstract:
The main goal of this thesis was to improve the knowledge on the mechanisms involved on Human dispersal of freshwater invasive fauna, contributing for the management of these problematic species. Several vectors were investigated, both accidental and intentional, from a freshwater invaders list that included some of the worse species. It was found that the red swamp crayfish and the signal crayfish presented desiccation survival capacities compatible with long-distance human-mediated dispersal. Off-road vehicles constituted a viable accidental vector for invasive macroinvertebrates, like the red swamp crayfish and the bladder snail. Live bait capture using dip nets and crayfish trapping constitute viable vectors for invasive freshwater macrofauna dispersal. The former is more related with accidental transport of small invasive organisms, and the latter is mostly related with intentional transport of invasive fish species. The importance of the angling web forums as a useful tool to help detection of non-native fish species was demonstrated with the first record of European Perch, a non-native fish in continental Portugal. Freshwater anglers from Portugal and Spain presented preference for invasive fish species, similar mobility, low incidence of live bait use and similar perception of biological freshwater invasions processes and impacts. Differences among countries were found for angler's activity patterns throughout the year and motivations for introductions. Zebra mussel larvae desiccation survival is compatible with long-distance overland dispersal. Its transport by natural vectors, like ducks, or human vectors like fishing tackle, such as waders and keep nets is viable. Yet, when comparing both types of vectors, fishing tackle presented a higher propensity to spread zebra mussel larvae than ducks; Dispersão de fauna invasiva dulçaquícola pelo Homem
Resumo:
O principal objetivo desta tese foi melhorar o conhecimento dos mecanismos envolvidos na dispersão de fauna dulçaquícola invasiva pelo homem, contribuindo assim para a gestão destas espécies problemáticas. Investigaram-se vários vetores, quer acidentais quer intencionais de uma lista de invasores dulçaquícolas que incluem algumas das piores espécies. Verificou-se que o lagostim vermelho e o lagostim sinal possuem uma capacidade de sobrevivência à dessecação compatível com a sua dispersão a longa distância pelo Homem. Os veículos todo-o-terreno constituem um vetor viável para macroinvertebrados invasivos como o lagostim vermelho e o caracol aquático. A captura de isco vivo com recurso a camaroeiro e o uso de armadilhas para a captura de lagostim constituem vetores viáveis de dispersão para a macrofauna dulçaquícola, sendo que o primeiro está relacionado com o transporte acidental de pequenos organismos invasores e o segundo com transporte intencional de peixes invasores. Através do primeiro registo em Portugal Continental de Perca-europeia, uma espécie não-nativa, demostrou-se a importância de fóruns on-line de pesca desportiva como uma ferramenta útil para a deteção de peixes não-nativos. Os pescadores dulçaquícolas de Portugal e Espanha apresentam preferência por espécies de peixes invasores, similar mobilidade, baixa incidência no uso de isco vivo e similar perceção dos processos e impactos das invasões biológicas dulçaquícolas. Detetaram-se diferenças entre países nos padrões de atividade dos pescadores durante o ano e na motivação para as introduções. A sobrevivência à dessecação de larvas de mexilhão-zebra é compatível com o seu transporte a longas distâncias fora de água, sendo viável o seu transporte quer por vetores naturais, como patos, quer humanos como equipamento de pesca, como botas altas e redes de retenção. No entanto, quando se comparam ambos os tipos de vetores, o equipamento de pesca apresenta maior propensão que os patos para dispersar larvas de mexilhão-zebra.
33
Alzoubi, Maref Yousef. "A dispersal model for structured populations." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/289042.
Full textAbstract:
We study a model for a structured population with a two-phase life cycle. Growth and reproduction occur during the first phase. The first phase is followed by a dispersal phase in which individuals are allowed to move throughout a habitat. We study the extinction and survival of the population from the bifurcation point of view. We prove the existence of positive equilibria and analyze their asymptotic stability near the extinction equilibria, relating it to the direction of bifurcation. Finally we investigate the spectrum of the branch of positive solutions.
34
Bunney, Katherine. "Seed dispersal in South African trees: with a focus on the megafaunal fruit and their dispersal agents." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/9191.
Full textAbstract:
Includes bibliographical referencesSeed dispersal is a key process. It is important in plant population biology because it influences the fate of seeds and the probability of recruitment, in plant biogeography since dispersal mode can influence the distribution range and rate of response to environmental change and habitat fragmentation, and in animal ecology since fruits can be an important dietary item (Wang and Smith, 2002). The majority of trees in the tropics (70 – 90%) and a large proportion of trees in temperate regions (up to 60%) rely on vertebrates for their dispersal (Howe and Smallwood, 1982; Fleming et al., 1987, Willson, 1990). Vertebrate dispersers range in size from 5g mistletoe birds (Dicaeidae) to 7,500,000g elephants (Elephantidae). The range and distribution of frugivore sizes is not uniform across ecosystems or geographical regions (Mack, 1993). These differences, one might suspect would be mirrored in the range and distribution of fruit size. This is not the case; in South America where the largest frugivorous mammal is the tapir (300kg; Hansen and Galetti, 2009), there is a subset of fruit that are conspicuously large. The paradoxical existence of such large fruit in the lowlands of Costa Rica was first noted by Janzen. In collaboration with Pleistocene faunal expert Paul Martin they conjectured that these fruit were ecological anachronisms that had evolved in the presence of large terrestrial vertebrates (>1000kg - megafauna) but had remained long after their demise (Janzen and Martin, 1982).
35
Will, Heidrun. "Modelling seed dispersal by animals development and application of a mechanistic simulation model for zoochorous seed dispersal." Berlin mbv, Mensch-und-Buch-Verl, 2008. http://d-nb.info/992966426/04.
Full text
36
Silva, Vanessa Mariano da. "O papel da limitação de sementes e da limitação no estabelecimento no recrutamento de plantas do cerrado." Universidade Federal de São Carlos, 2015. https://repositorio.ufscar.br/handle/ufscar/8368.
Full textAbstract:
Submitted by Maria de Lourdes Mariano (lmariano@ufscar.br) on 2017-01-12T17:18:37Z
No. of bitstreams: 1
SILVA_Vanessa Mariano_2015.pdf: 1028554 bytes, checksum: b983689081dffe8a634db905adc7c152 (MD5)Approved for entry into archive by Maria de Lourdes Mariano (lmariano@ufscar.br) on 2017-01-12T17:19:59Z (GMT) No. of bitstreams: 1 SILVA_Vanessa Mariano_2015.pdf: 1028554 bytes, checksum: b983689081dffe8a634db905adc7c152 (MD5)
Approved for entry into archive by Maria de Lourdes Mariano (lmariano@ufscar.br) on 2017-01-12T17:20:07Z (GMT) No. of bitstreams: 1 SILVA_Vanessa Mariano_2015.pdf: 1028554 bytes, checksum: b983689081dffe8a634db905adc7c152 (MD5)
Made available in DSpace on 2017-01-12T17:20:15Z (GMT). No. of bitstreams: 1 SILVA_Vanessa Mariano_2015.pdf: 1028554 bytes, checksum: b983689081dffe8a634db905adc7c152 (MD5) Previous issue date: 2015-12-18
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Plant recruitment can be constrained by seed and establishment limitation and these processes can affect community species composition and diversity. In Neotropical savannas the relative importance of these processes for plant regeneration are unclear because of the scarcity of studies. The aim of this study was to evaluate the importance of seed and establishment limitation to plant recruitment on cerrado savanna in Itirapina, southeast Brazil (22°12´S, 47°52´W). We spread 49 seed traps in a 0.64-ha plot and monitored seed rain monthly for a year, and also conducted seed addition experiments. Seed production presented a peak in rainy season, with zoochoric and anemochoric species producing seeds mainly in rainy and dry season respectively. Our study indicates a strong influence of seed limitation on recruitment, with most seed rain species presenting seed limitation values higher than 65%. Only 23% of woody species in the plot had at least one seed trapped. Seed and source limitation was negative related to adult abundance, indicating that the increase of seed sources enhances the number of suitable sites reached by seeds. There was no relation between seed, source and dispersal limitation and plant life form, dispersal syndrome and seed mass. Seed addition was unable to increase seedling regeneration in the four species tested, which presented high values of establishment limitation. Our study shows that Neotropical savanna plants recruitment is restricted by seed and establishment limitation and highlights the role of seed production and dispersal to colonization of new sites.
O recrutamento de plantas pode ser restringido pelas limitações de sementes e no estabelecimento, os quais afetam a composição e diversidade de uma comunidade. Em savanas neotropicais a importância relativa desses processos ainda não é clara em decorrência da falta de estudos. O objetivo desse estudo foi avaliar a importância das limitações de sementes e no estabelecimento para o recrutamento de uma comunidade de cerrado no sudeste do Brasil. Foram posicionados 49 coletores de sementes em uma parcela de 0,64 ha e a chuva de sementes foi monitorada mensalmente durante um ano. Além disso, foram realizados experimentos de adição de sementes. A produção de sementes apresentou um pico durante a estação chuvosa, sendo que as espécies zoocóricas produziram principalmente durante a estação chuvosa e as anomocóricas, durante a estação seca. Houve uma influência significativa da limitação de sementes no recrutamento, sendo que a maioria das espécies presentes na chuva de sementes apresentou valores dessa limitação maiores que 65%. Apenas 23% das espécies arbustivo-arbóreas presentes na parcela tiveram, pelo menos, uma semente coletada. As limitações de sementes e na fonte apresentaram uma relação negativa com o número de adultos, indicando que o aumento de fontes de sementes eleva o número de locais atingidos por sementes. Não houve relação entre limitações de sementes, na fonte e na dispersão com forma de vida, síndrome de dispersão e peso da semente. A adição de sementes não aumentou a regeneração de plântulas das quatro espécies testadas, as quais apresentaram valores elevados de limitação no estabelecimento. O presente estudo indica que o recrutamento de plantas de savanas neotropicais é restringido pelas limitações de sementes e no estabelecimento e ressalta a importância da produção e dispersão de sementes para a colonização de novos locais.
37
Lapenta, Marina Janzantti. "Frugivoria, Dispersão Primária e Secundária de Sementes Consumidas por Micos-Leões-Dourados (Leontopithecus rosalia) na Reserva Biológica União, RJ." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/41/41134/tde-20072007-144301/.
Full textAbstract:
Os animais frugívoros podem influenciar padrões de distribuição espacial de plantas jovens e adultas, mas parte do recrutamento de uma população vegetal é perdida pela predação de sementes, sendo esta a principal força ecológica e evolutiva que afeta as comunidades vegetais. A maioria das sementes dispersadas por primatas na floresta é morta por predadores de sementes ou movida por dispersores secundários, alterando a sombra de sementes original. Pouco se sabe sobre as interações complexas entre a dispersão e predação de sementes, visto que poucos trabalhos foram realizados sobre a relação entre a dispersão de sementes por frugívoros, e a distribuição das plântulas das espécies consumidas. Para que Planos de Conservação possam ser desenvolvidos, as relações entre a fauna de frugívoros e a vegetação, e a estrutura das Florestas Tropicais devem ser bem entendidas. Na Reserva Biológica União dois grupos de micos-leões-dourados foram acompanhados mensalmente durante três dias cada um, de abril de 2003 a março de 2004 do momento em que deixaram o local de dormida, até o fim de suas atividades no final do dia. Outros grupos foram acompanhados esporadicamente entre agosto de 2004 e janeiro de 2005. Todas as árvores visitadas foram marcadas e amostras dos frutos foram coletadas para identificação e experimentos de germinação. As sementes retiradas dos frutos foram colocadas para germinar em comparação com sementes provenientes das fezes dos micos, ou sementes cuspidas por estes. As sementes foram acompanhadas na mata, quanto à germinação, desaparecimento ou dispersão secundária, predação, mortalidade, sobrevivência e estabelecimento de plântulas. Além disso, foi feito o acompanhamento fenológico de 791 árvores de espécies consumidas pelos micos-leões, de julho de 2003 a junho de 2004. Durante o período de estudo os grupos se alimentaram de 88 espécies de frutos de pelo menos 18 famílias, engolindo as sementes de 43 espécies e cuspindo as sementes de 45 espécies. Cento e sete experimentos foram realizados com 1711 sementes de 38 espécies de frutos (28 espécies de sementes engolidas e dez espécies de sementes cuspidas). No período de estudo mais de 50% das sementes (> 3 mm) dos experimentos desapareceram e cerca de 15% morreram antes de germinar. Vinte e duas espécies tiveram sementes germinando na mata e desenvolveram plântulas, mas no final do estudo apenas 15 dessas espécies ainda apresentavam plântulas sobreviventes. Para melhor se estabelecer se os predadores ou dispersores secundários das sementes depositadas pelos micos-leões-dourados são vertebrados ou invertebrados foram montados experimentos com gaiolas de exclusão de sementes. Outros aspectos quantitativos e qualitativos da dispersão de sementes foram analisados, incluindo a caracterização das deposições, tempo de passagem das sementes pelo trato digestório dos micos, distância e habitat de dispersão e outros. O mico-leão-dourado (Leontopithecus rosalia) é uma espécie frugívora e endêmica da Mata Atlântica, e o presente estudo é o primeiro a acompanhar a sobrevivência e crescimento de plântulas provenientes das fezes desse primata, detalhando a sua importância como dispersor de sementes. Estudos sobre o destino das sementes defecadas são fundamentais para a conservação do mico-leão e do seu habitat, a Mata Atlântica de baixada costeira do estado do Rio de Janeiro, um dos ecossistemas mais ameaçados do planeta.The frugivores may influence spatial patterns of adults and juvenile plants, and a great portion of the potential recruitment of plant populations is lost to seed predators. The majority of seeds dispersed by primates on forest is killed by seed predators or moved by secondary dispersers. Little is known about the complex interaction between seed dispersal and post-dispersal seed-predation, and few researches were done on the relation between seed dispersal by animals and seedling distribution of exploited plant species. The golden-lion-tamarin (Leontopithecus rosalia) is a frugivorous endemic species of Atlantic Forest. This research will be the first to consider the survivor and establishment of seedlings from golden-lion-tamarins feces, studying the importance of this primate as seed disperser, ensuring the preservation of the Atlantic Forest, one of the most threatened ecosystems in the world. Two groups of golden lion tamarins were monthly studied in the União Biological Reserve three days each one, from April 2003 to March 2004 since left sleeping site until finished their activities at the end of the day. Other groups were sporadically monitored from August 2004 to January 2005. All visited trees were marked and samples of fruits were collected for identification and germination experiments. Seeds from fruits and from tamarins feces or spitted out were put to germinate. The seeds were studies to verify the germination, disappearance or secondary dispersion, predation, mortality and survival and establishment of the seedlings. Beside that, 791 trees from eaten species were studied from July 2003 to June 2004 to collect phenological data. During study period the groups ate 88 fruit species from at least 16 families, ingesting seeds of 43 species and spitting seeds from 45 species. A Hundred and seven experiments were conducted with 1711 seeds of 38 fruit species (28 species of ingested species and 10 species of spitted seeds). During study period more than 50% of seeds (> 3 mm) disappeared from experiments, and about 15% died before germinating. Twenty two species had seeds germinating on forest and until seedling stage, but at the end of the study only 15 of these species still had seedling surviving. To determine if the seed predators or secondary dispersers of seeds deposited by tamarins are vertebrate or invertebrate, experiments with seed exclosure cage were established. Others qualitatively and quantitatively aspects of seed dispersal were considered, including feces deposition, time of gut passage, distance and habitat of seed deposition and others. The golden lion tamarin (Leontopithecus rosalia) is a frugivore and endemic species of Atlantic Forest and this study is the first to attend the survival and establishment of seedlings from tamarins feces, and the tamarins importance as a seed disperser. Studies on seed fate are important to the conservation of golden lion tamarins and his habitat, the lowland Atlantic Forest of the state of Rio de Janeiro, one of the most endangered ecosystems in the world.
38
Hawes, Nicola Ann. "Nearshore Dispersal and Reproductive Viability of Intertidal Fucoid Algae : how effective is drift in local to regional dispersal?" Thesis, University of Canterbury. School of Biological Sciences, 2008. http://hdl.handle.net/10092/2103.
Full textAbstract:
The ecological importance of drifting will depend on the abundance of drifting algae and whether it is reproductively viable. However, the ability of adult plants to successfully disperse long-distances by drifting is largely unknown, particularly for fucoids. The abundance, species composition, and reproductive status of drifting algae was examined by transect surveys around Kaikoura and Banks Peninsula. Abundance and species composition varied between sites, but all drifting algae that were in reproductive season, and had reproductive structures intact, were reproductively active. The reproductive longevity and viability of drifting and beach-cast Hormosira banksii, Durvillaea antarctica and Cytophora torulosa was compared with attached populations. Drifting algae remained reproductively viable, and fecundity did not differ from that of attached algae. Viable propagules were released from drifting algae for the duration of the experiments (H. banksii 57 days, D. antarctica 62 days, and C. torulosa 43 days). In contrast, beach-cast algae ceased to release propagules after 14 days. Dispersal by drifting relies on offshore transport after detachment. To determine the influence of wind and tidal currents on the nearshore transport of drifting algae, tagged H. banksii, D. antarctica, C. torulosa and GPS-tracked drifters were released from shore. Drifters generally moved in the direction of the prevailing wind, but some influence of tidal direction and bathymetry was detected. Offshore winds and outgoing tides were favourable for the offshore transport of surface drifting algae. Following dispersal and arrival at new locations, the distance between gametes may be important in determining the fertilisation success of dioecious species. Experiments testing the fertilisation success of H. banksii and D. antarctica, over increasing distances, showed that fertilisation success decreased with increasing distance between male and female gametes. Despite this, eggs were fertilised when male and female gametes were up to 2m apart, and sperm remained viable for 2 hours.
39
Bartumeus, i. Ferré Frederic. "Lévy Processes in Animal Movement and Dispersal." Doctoral thesis, Universitat de Barcelona, 2005. http://hdl.handle.net/10803/1424.
Full textAbstract:
ENGLISH ABSTRACT:The general aim of this thesis was to develop a theoretical framework in order to study large-scale animal movements and/or dispersal processes as random search strategies. The framework was based on statistical physics methods and concepts related to a class of stochastic processes based on the Lévy-stable distribution (the so-called Lévy processes). In particular, we modeled animal movement and dispersal processes by means of a new class of random walks based on the Lévy-stable distribution (the so-called Lévy flights). Lévy flight models introduce two relevant long-term statistical properties: super-diffusion and scale invariance. Both phenomena have been observed in large-scale animal movement and dispersal data, and impinge directly into organisms' encounter probabilities at both individual (e.g., search strategies) and population (e.g., colonization of new habitats) organizational levels. The approach is novel not only because of the methodology used (based on the statistical physics related to Lévy processes), but also because it is founded on statistical principles usually understated in animal ecology. To achieve this general objective we carried out three main studies, which define the main parts of the thesis.
First, we quantified the variations in encounter rates due to the statistical properties provided by Lévy walking particles in spatially explicit systems. We carried out a series of numerical simulations in spatially explicit systems (1D, 2D, and 3D) where randomly moving particles (Lévy random walkers) must find each other. The simulations were meant to represent different encounter scenarios and different encounter dynamics: destructive and non-destructive. We showed that in certain scenarios encounter rate variation was shaped by the nature of the statistical properties of movement rather than by physical aspects of the particles (organisms) such as size or velocity. In particular, super-diffusion and scale invariance were relevant at low resource densities and/or when the search processes involve low spatial dimensionality. We also showed how the movement trajectories of the searching particles could be optimized depending on the type of encounter dynamics (destructive or not), and the mobility of the target particles (i.e., both velocity and super-diffusive properties).
Second, we studied how and why Lévy flight properties (i.e., scale invariance, and super-diffusion) should be sustained by specific animal movement mechanisms. We showed an organism capable to adjust its search statistics as a function of resource concentration. As resource decreased the marine heteroflagellate Oxhyrris marina changed from a Brownian to a Lévy search statistics. Changes in the helical component of the animal movement were also tracked and interpreted. The biological mechanism allowing the main statistical change was also identified: the transient arrests of the longitudinal flagellum provided scale invariant intermittence to the movement. Assuming random walk models as a necessary tool to understand how animals face environmental uncertainty, we also analyzed the statistical differences between Lévy walks and another type of random walk models commonly used to fit animal movement data, the correlated random walks. This analysis allowed us to understand better why we should expect Lévy flight statistical properties to be behaviorally adaptive in living organisms.
Third, we establish a link between the individual and the population level of organization by modeling "population dispersal strategies" as Lévy processes. A Lévy-dispersal kernel is the one based on a Lévy-stable distribution. We modeled (meta) population dispersal strategies by means of Lévy-dispersal kernels. In particular, we studied how different Lévy flight dispersal strategies are optimized depending on the underlying landscape architecture (e.g., spatial correlation, fragmentation, etc.). Finally, as a first step towards the introduction of Lévy-dispersal kernels in the context of metapopulation theory, we developed a model (both numerical and analytic) to study the role of dispersal range in the persistence and dynamics of metapopulations living in fragmented habitats.
EN CATALÀ:
L'objectiu principal d'aquesta tesi va ser desenvolupar un marc teòric basat en mètodes i conceptes de física estadística per tal d'estudiar el moviment animal i els fenòmens de dispersió. A escales espacio-temporals grans, el moviment dels animals i els fenòmens de dispersió poden ésser entesos com a processos de cerca a l'atzar. Concretament, nosaltres hem modelat el moviment animal i els processos de dispersió en base a una classe de passeigs a l'atzar coneguts com a vols de Lévy que es fonamenten en la distribució estable de Lévy. Els vols de Lévy s'inclouen en una classe més àmplia de processos estocàstics tots ells basats en la distribució estable de Lévy i que reben el nom genèric de processos de Lévy. Els vols de Lévy introdueixen en el món dels passeigs a l'atzar dues propietats estadístiques rellevants: la super-difusió i la invariànça d'escala. Tots dos fenòmens han estat descrits en relació al moviment dels animals a gran escala i/o en relació a certs processos de dispersió. Tots dos fenòmens tenen implicacions directes sobre les probabilitats d'encontre tant a nivell individual (processos de cerca de recursos) com a nivell poblacional (processos de colonització d'habitats fragmentats). L'aproximació al problema del moviment animal i la dispersió proposada en aquesta tesi, no només és novedosa en el sentit estrictament metodològic (i.e., aplicació de la física estadística i dels processos de Lévy al moviment animal), sinó també perquè es basa en una sèrie de principis estadístics que fins ara no han estat considerats en l'estudi del moviment animal.
Les principals conclusions que es poden extreure del treball realitzat són: 1) les propietats estadístiques lligades als processos de tipus Lévy (i.e., super-difusió i invariànça d'escala) incrementen les taxes d'encontre en situacions de cerca a l'atzar, 2) existeixen organismes capaços de provocar l'emergència d'aquestes propietats estadístiques en una situació de cerca a l'atzar, 3) a nivell poblacional, fenòmens de dispersió de tipus Lévy incrementen la taxa de colonització en hàbitats molt fragmentats, i 4) la dispersió de llarg abast facilita l'existència de metapoblacions en hàbitats fragmentats.
40
Ryan, Daniel P. "Fitness Dependent Dispersal in Intraguild Predation Communities." Scholarly Repository, 2011. http://scholarlyrepository.miami.edu/oa_dissertations/608.
Full textAbstract:
A model of a three species intraguild predation community is proposed. The model is realized as a system of cross-diffusion equations which allow the intraguild prey species to adjust its motility based on local resource and intraguild predator densities. Solutions to the cross-diffusion system are shown to exist globally in time and the existence of a global attractor is proved. Abstract permanence theory is used to study conditions for coexistence in the ecological community. The case where the intraguild prey disperses randomly is compared to the case where the intraguild prey disperses conditionally on local ecological fitness and it is shown that the ability of the intraguild prey to persist in the ecological community is enhanced if the intraguild prey utilizes a movement strategy of avoiding areas with negative fitness. A finite element scheme is used to numerically simulate solutions to the system and confirm the analytical results.
41
Fogelqvist, Johan. "Genetic structure and dispersal in plant populations." Doctoral thesis, Uppsala universitet, Institutionen för evolution, genomik och systematik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9211.
Full textAbstract:
This thesis focuses on the spatial structure and methods to identify spatial structure in plants. Methods that investigate genetic structure can mainly be divided into equilibrium methods that reveal summed dispersal over many generations, and cluster methods, that reveal more recent dispersal events. Depending on the spatial level, local or global, suitable methods are different. The thesis consists of four papers. The first explores the spatial genetic structure in two epiphytic bryophytes that have different dispersal strategies (Orthotrichum speciosum and O. obtusifolium) using three different approaches based on pairwise kinship coefficients assessed from AFLP data. The spatial kinship structure was detected with both autocorrelation analysis and generalized additive models, but linear regression failed to detect any structure in O. speciosum. In the second paper the spatial genetic structure in marginal populations of the forest tree Quercus robur is investigated at both local and regional scales. At the local scale, dispersal kernels as estimated using maximum likelihood parentage methods showed to be comparable to results acquired in central located populations. At the regional scale the degree of isolation at the margin of the distribution is shown. The third paper compares a number of sibship clustering methods. It was found that the performances of the sibship reconstruction algorithms are strongly dependent on fulfilling the assumptions of the model and that using an overly simple model produced very unreliable results. The amount of information included in the model affected the results; models including all the available information outperformed the models using only a subset of the information. In the last paper we show that the number of clusters as estimated by the software Structurama depends on sample size. At high number of subpopulations, the estimated number of clusters tends to be grossly underestimated when the number of sampled individuals per subpopulation is low.
42
Astini, Juan Pablo. "Managing maize pollen dispersal and out-crossing." [Ames, Iowa : Iowa State University], 2007.
Find full text
43
Uzcategui, Cuello Nathalie Yumari. "Evolution and dispersal of mosquito-borne flaviviruses." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288520.
Full text
44
Bolland, Jonathan David. "Factors affecting the dispersal of coarse fish." Thesis, University of Hull, 2008. http://hydra.hull.ac.uk/resources/hull:1366.
Full textAbstract:
Globally, freshwater fisheries are faced with numerous impacts that compromise fish populations. A knowledge and understanding of riverine fish movements are crucial for effective management and conservation of populations. However, there is a paucity of information about the spatial behaviour and ecology of wild and stocked cyprinids in floodplain rivers, especially under the influence of elevated flows. This study examined the factors affecting the lateral and longitudinal dispersal of juvenile and adult (wild and stocked) coarse fish in three lowland river catchments, namely the River Trent, the Yorkshire Ouse and the River Roding.A literature review was carried out to review the influence of floods on riverine ecosystem function and structure, and fish assemblage patterns. In unmodified lowland rivers, floods are characterized by lateral expansion onto floodplains resulting in high levels of habitat heterogeneity, essential for fish refuge, spawning, nursery and feeding. However, anthropogenic alterations to the flow regime and floodplain connectivity have had considerable detrimental impacts on fish populations. The main conclusion of the review was the need to restore and rehabilitate lowland rivers in an attempt to recover natural features or functionality. The effects of flood timing and magnitude were examined by sampling 0+ fish populations before, during and after floods in the Yorkshire Ouse, a constrained lowland river. Large numbers of eurytopic 0+ fishes were stranded on isolated floodplains when artificial levees ‘over-topped’ in summer (August). By contrast, backwaters provided refuge for high densities of 0+ eurytopic and rheophilic fishes. During floods, small fish were displaced or had lower survival. The results highlight the influence of flood timing on 0+ fish populations, the use of refuge areas and their importance of lowland river rehabilitation.In the River Trent, 0+ fish populations were sampled in the margins of the main river channel and in ten man-made floodplain waterbodies to evaluate the importance of variable connectivity between these habitats for rehabilitating the riverine-floodplain ecosystem. Fish assemblages compared favourably with studies on unmodified river reaches, i.e. succession of lotic-to-lentic habitat corresponded to a sequence of rheophilic-to-eurytopic-to-limnophilic fish species. Consequently it was concluded that the connection of man-made floodplain waterbodies to the river should incorporate variable, not just high, levels of hydrological connectivity into holistic riverine ecosystem management plans.Dual-Frequency Identification Sonar (DIDSON) was used to determine the influence of elevated flow on the lateral movements of adult fish between the Yorkshire Ouse and a marina (refuge habitat). Fish activity in the entrance was predominantly during daylight hours. Increased river flow resulted in significantly reduced fish movements, both towards and away from the marina, and fish presence in the entrance, except for larger fish (more than 30 cm) during the night. This study emphasised the importance of artificial floodplain waterbodies for adult cyprinid fish during winter months.The influence of environmental variation (flow and temperature) on movements of wild and stocked adult cyprinids is poorly understood, partially because of experimental difficulties. A laboratory study on PIT tagging individual juvenile cyprinids, identified that the method would be suitable for such investigations. In the River Roding, a combination of PIT and radio telemetry was used to compare habitat use, longitudinal movement (timing and direction), site fidelity and survival between wild populations and hatchery-reared fish. Wild cyprinids had high levels of ‘site fidelity’ but highly mobile individuals were present within the population, with movements positively correlated with temperature and flow. During elevated winter flows, wild fish occupied areas of reduced flow to reduce energy expenditure, but some fish performed exploratory movements. Movements of stocked fish were more frequent and longer than for wild fish, particularly just after release, possibly for exploratory purposes. Subsequently, movements of stocked fish were minimal, did not correlate with flow or temperature and the final distributions were more widely dispersed than found in wild fish. Importantly from a stocking perspective, stocked cyprinids had the behavioural and physiological ability to cope with elevated flows. However, differences in movements and habitat use between wild and stocked chub probably had consequences on survival.
45
O'Connor, Sarah-Jane. "Quantifying seed dispersal of matai (Prumnopitys taxifolia)." Thesis, University of Canterbury. Biological Sciences, 2012. http://hdl.handle.net/10092/7836.
Full textAbstract:
In New Zealand’s highly modified environment, it is unclear how ecological services function
within modified habitats and with an altered suite of mutualists and predators. I used matai
(Prumnopitys taxifolia) to investigate the status of dispersal including the range of native and
introduced species involved, and to test the feasibility of using microsatellites (repetitive regions
of DNA) to identify maternal origin of seeds and therefore measure dispersal. I isolated
ten microsatellite loci, five of which were polymorphic. Across 20 adult matai on Banks Peninsula,
none shared a multi-locus genotype across these five loci; this suggests that these loci will
be sufficiently variable to allow the individual identification required for parentage analysis. Although
logistic problems prevented full testing of the system, preliminary results suggest that
these microsatellites will allow identification of the maternal parent of seeds genotyped from
their seed coat. Seed traps and ground plots throughout forest fragments on the Port Hills found
varying levels of insect (0–19%) and rodent (0–1.5%) pre-dispersal predation over two years;
despite this, 19–55% of seeds caught beneath female matai trees had been consumed and excreted
by a bird. The majority of seeds (98%) were caught within 55 m of the nearest female
matai tree, with a maximum distance of 130 m, indicating dispersal was occurring within these
sites. Through observations on fruiting trees, I found four bird species regularly visited and fed
on matai fruits; native kereru (Hemiphaga novaeseelandiae) and bellbird (Anthornis melanura),
and exotic blackbird (Turdus merula) and song thrush (T. philomelos). As expected, kereru performed
the majority of feeding visits (50%), but surprisingly the two introduced species combined
contributed 22% of the feeding visits. I argue that the prevailing methods for measuring
avian frugivory systematically under-estimate the contribution made by introduced birds. This
finding is important as Turdus species are abundant and widespread in New Zealand. Finally,
I examined whether feral pigs (Sus scrofa) disperse seeds of matai. Both captive and wild pigs
consumed matai seeds and excreted a proportion of these intact; germination rates of these
seeds (57–68%) were comparable to hand-cleaned seeds (64%). This is the first demonstration
of feral pigs dispersing the seeds of a New Zealand native plant. Large mammals such as pigs
may provide long distance dispersal of fleshy-fruited species, which will be particularly important
in today’s highly fragmented forests. Further dispersal research should consider the effects
of these introduced avian and mammalian dispersers if we are to understand how ecological
services are functioning amidst our modified environments.
46
Krug, Rainer Michael. "Modelling seed dispersal in restoration and invasions." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/1155.
Full textAbstract:
Thesis (PhD (Conservation Ecology and Entomology))--Stellenbosch University, 2008.Dispersal plays an essential role in determining the distribution of populations of species, especially species expanding their ranges. Two disciplines are concerned with gaining understanding of spread of species, namely restoration ecology and invasion biology. Con- ceptual understanding of dispersal, its mechanisms and its management is essential to both disciplines. Nevertheless, the disciplines have quite opposite objectives: in restoration ecol- ogy, spread of indigenous species into transformed landscapes is promoted, while invasion biology aims to prevent the (further) spread of alien species into pristine or restored habi- tats. Despite these two opposite objectives of facilitating spread and preventing spread of their respective target species, these disciplines have essentially the same requirements in terms of information needed for restoration. In this thesis, I will present two modelling studies—one looking at the impact of two different seed-feeding alien control agents on the spread of Hakea sericea, the other investigating the recolonisation by Dicerothamnus rhinocerotis of an old field dominated by Cynodon dactylon. Based on these studies, I will draw conclusions for the management in each case. In a second step, I will compare these two seemingly-different studies and draw conclusions on how these two disciplines can learn from each other, and how conclusions drawn and management recommendations developed for the one discipline can be translated for the other. The invasion biology study concluded that seed-feeding biocontrol agents do have a considerable impact on the velocity of the spread of the target species. In addition, management recommendations included the possibility of substituting seed-feeding biocontrol agents with an increased fire frequency where the negative impact on natural vegetation, on the site invaded by the target species, is acceptable. The restoration study concluded that the main impact on the velocity of spread, and the speed of the return of the shrub species onto the old fields, is the availability of micro-sites. A sensitivity analysis showed the even a slight change from 1% to 2% increases the velocity and pattern of spread dramatically. The other parameters playing an important role are the mean rate of establishment and the time span between
47
Adeniran, Oluwafisayo Hazeezat. "Determinants of grasshopper dispersal : an experimental approach." Thesis, Swansea University, 2014. https://cronfa.swan.ac.uk/Record/cronfa43157.
Full textAbstract:
Understanding and predicting animal movements is of crucial importance for the conservation and management of natural resources. Grasshoppers are ecological indicator species used to monitor the spatio- temporal changes, to help reduce further loss of biodiversity on open grasslands. However, their current decline on European landscapes as a consequence of intense agricultural practices has elicited the need to understand all aspects of their ecology especially their movement on these highly fragmented landscapes. With the use of a mesocosm, a mark and re-sight study was conducted in the Poitou Charentes Region of Western France, to investigate the movement dynamics of three widespread species in that area. With emphasis placed on the determinants of their rate and scale of movement in addition to the influence of individual behavioural trait variations on dispersal plasticity. Net square displacement and mean squared displacement was used to quantify rate and pattern of movement. Two sub populations were identified and classified as settled and yet to settle sub- population. Poisson regression analysis and generalized linear models were used to test significance of interactions between grasshopper species and microhabitat constituents. Average distance travelled by re-sighted individuals ranged from 3.50metres to 18.66 metres. However the variation in average distance estimated for each of the species, arose from species specific interactions with micro habitat conditions especially vegetation functional class found within the quadrat. Inter specific differences due to the possession of morphological correlates with dispersal; large body size and wing development, explained variation in magnitude of dispersal especially between C.dorsatus and P.giornae. However the rate of displacement exhibited by E.elegantulus suggest that possession of these traits in relation to proximity to food resources influences dispersal kernel. The study was conducted during grasshopper breeding season when sex specific reproductive traits were likely to be more apparent. As a result of this, average distance travelled by male individuals exceeded that of females, but then these differences were not statistically significant.
48
Arzt, Alexandra E. "Dispersal: a multidisciplinary investigation of plant life." VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/3957.
Full textAbstract:
Using plants as a basis for exploring the interstices between the human and nonhuman, this thesis investigates ideas of awareness, intelligence, deep time, animism, and the fluctuating human perception of the agency of Nature. It outlines environmental art practices since the 1950s involving vegetal life. In addition, the paper provides a critical analysis of plant perception of Jakob von Uexküll’s work and theories of vital materialism and “critical plant studies” while noting recent studies in plant neurobiology. In my work, plants become active participants via their movement, seeding, and smell. This study takes the form of imitation, purposeful symbiosis, anthropomorphism, and touch and uses an interdisciplinary practice involving various experiments, video, and plant life. In suggesting a new possible understanding of plants, the work argues for a new ecological ethos in a time when global warming weighs heavily on world policy and consciousness.
49
Maxwell, Christopher Luke. "The dispersal of the Hamilton Palace collection." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5197/.
Full textAbstract:
By the penultimate decade of the nineteenth century, the Dukes of Hamilton, premier peers of Scotland, had amassed a superb collection of fine and decorative art. This outstanding collection was dispersed in two series of sales in 1882 and 1919, and the family’s principal seat, Hamilton Palace, ten miles south of Glasgow, was demolished in the 1920s and ′30s. Many of the most significant items are now in the great museums, galleries and libraries of the world or in important private collections. This study will begin by identifying the causes of the 12th Duke of Hamilton’s financial difficulties and the chain of events leading to the dispersal of the collection, with a comparative analysis on the backgrounds of the earlier enforced sales of Fonthill Abbey (1822), Wanstead House (1822), Strawberry Hill (1842), and Stowe (1848). It will continue with a thorough investigation of selected principal beneficiaries, what they acquired and why. These will include Christopher Beckett Denison; various members of the Rothschild family; William Dodge James; the 5th Earl of Rosebery; Sir Michael Shaw-Stewart; and the 5th Earl of Carysfort. A survey of the records of certain national museums and galleries will establish the involvement of the museum sector in the dispersal of the collection, with a review of these institutions’ acquisitions. Finally, this study will consider the extent to which North American collectors benefited from the sales through the international art trade between 1880 and 1930, culminating in an account of the purchase of the Hamilton Palace interiors by the New York dealers, French & Co., and their subsequent acquisition by the newspaper magnate and collector William Randolph Hearst. This research will add a new perspective to the understanding of the break-up of this renowned collection, and of the loss to Scotland’s material culture and heritage. It will contribute to current scholarship on nineteenth-century house sales and increase current knowledge of the socio-economic causes and effects of such events. The question of who benefited from the Hamilton Palace sales will be a new and original area of research within History of Collecting studies, contributing to a fuller appreciation of British collecting between 1880 and 1930 and of the international art trade and market from 1880 to the present day.
50
Jones, Mary Beatrix. "Likelihood inference for parametric models of dispersal /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/8934.
Full text