Thèses sur le sujet « Interactions entre espèces »
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Thomas, Anaïs. « Interactions entre espèces en plantations mélangées forestières et agroforestières ». Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0079.
Texte intégralPlantations of fast-growing species (e.g. poplars, willows, eucalyptus) are widely used for biomass supply. However, these plantations are often monospecific systems and are generally very resource demanding. This is particularly the case for plantations of species belonging to the Populus genus, which can be grown under intensive cultivation conditions, and which use large quantities of water and nitrogen to produce large volumes of biomass. In this context, mixed forest or agroforestry plantations appear as an interesting alternative to monocultures. Indeed, they can produce more by using more efficiently the resources necessary for the growth of the different components of the mixture by playing on the complementarity between the species. The introduction of nitrogen-fixing species in these mixtures can also be an additional asset to reduce the need for synthetic nitrogen inputs.In any plantation, forest or agroforestry, intraspecific interactions (individuals of the same species) or interspecific interactions (between individuals of two different species) can be negative, positive, or neutral. To date, the interactions between species that determine whether a given mixture will be more productive than the corresponding monocultures are still poorly understood and studies of their impact on resource-use efficiency are scarce. The overall objective of the PhD work was to evaluate the impact of several species mixtures, both forest and agroforestry, on tree growth performance through effects on functional (resource-use efficiencies), structural (crown architecture) and phenological (spring and fall bud and leaf phenology) determinants. The main hypothesis was that thanks to symbiotic nitrogen fixation and complementarity between species, trees in mixtures would be more productive and use resources more efficiently than in monoculture.This objective was pursued on an instrumented plantation on the La Bouzule site (54), installed in spring 2014, composed of mixtures of woody (poplars and alders) and herbaceous (legumes, graminoids) species, as well as their respective monocultures. The functioning of three types of mixtures including nitrogen-fixing species (poplars/alfalfa - clover succession; poplars/alders; alders/cereal - temporary grassland succession) was compared with monocultures of the two woody species. The originality of the work lies on the combination of the study of processes occurring at the organ and tree scales to describe the interaction processes between species and the overall performance of the different types of mixtures, compared to their respective monocultures.Species interactions in a plantation are not static but change as the stand develops. The nature of the interactions between poplars and legumes in the agroforestry plot evolved from a predominant competition at the beginning of the plantation to facilitation through soil nitrogen enrichment. The growth performances of the poplars were increased compared to the monoculture, associated with a higher water-use efficiency than in monoculture and a reduction of competition between the canopies allowing a better interception of light in agroforestry. In contrast, higher water-use efficiency of poplars associated with alder than in monoculture was not associated with better growth performances of both species compared to their respective monocultures. Overall, alder was only slightly affected by the mixtures
Ndome, Hameth. « Étude théorique des collisions réactives entre espèces diatomiques ». Marne-la-Vallée, 2007. http://www.theses.fr/2007MARN0375.
Texte intégralMonmeyran, Amaury. « Étude expérimentale d’un modèle de biofilm bactérien multi-espèces en vidéo-microscopie : cinétique de formation et interactions entre espèces ». Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS242.
Texte intégralDuring my PhD work, I characterized the development of a multi-species biofilm in milli-fluidic channels under constant flow of nutrient medium. I first developed the use of a new fluorescent reporter on a single-species Escherichia coli biofilm. I have shown the limitations of classical GFP type reporters on the system and introduced the inducible fluorescence protein FAST to overcome these limitations. With this new tool, I studied the formation of a multi-species biofilm, resulting from a natural biofilm adapted to the laboratory, consisting of Bacillus thuringiensis (Bt), Pseudomonas fluorescens (Pf), Kocuria salsicia (Ks) and Rhodocyclus sp. (R). I characterized the development of this adherent community by video-microscopy of transmitted light and fluorescence, by measuring in real time the kinetics of development of global biomass and fluorescent species within the community. I thus highlighted a succession of phases of growth and recession of the biofilm, then the establishment of stationary state after 30h of growth. I also found that Pf, numerically the dominant species of this community, operates after a few hours a change of niche probably giving him an important advantage. These results led me to formulate the hypothesis that the formation mechanism of this adherent community is largely governed by the equilibrium of O2 in the system. Finally, I have studied the different combinations that can be formed by members of the community in search of existing interactions between bacteria. I was able to show the existence of competitive interactions between Pf and Bt, the parasitism relation of Bt on Ks, as well as that of amensalism of Pf on Ks. We also determined that R develops in a neutral way towards the other species. Our results suggest that these interactions are mainly based on physical interactions and physicochemical regulation
Cougoul, Arnaud. « Analyse statistique de réseaux d'associations entre espèces microbiennes à partir de données métagénomiques ». Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC103.
Texte intégralHigh throughput sequencing reveals a new ecology of microorganisms. They are everywhere and their functions are essential for their host ecosystems, organisms or environments. Metagenomics makes it possible to estimate the composition and abundance of microbial species from a set of samples of the same type of microbial communities. In the studies that seek to understand the diversity and structure of such communities, network approaches can identify statistical associations between microbes, assuming that these statistical associations reflect biological interactions. In this context, the subject of my thesis was to better understand the potential of network approaches in the detection of associations between OTUs within metagenomic data and to develop the necessary tools to improve the analysis of datasets. As a first step, I studied the practices and analysis tools that can be used to infer association networks within metagenomes. Given the properties of metagenomic data, I determined their effectiveness and their limits. This work allowed me to identify ways to improve the study of microbial associations. Based on the accumulated knowledge, I developed an association analysis package between OTUs (named MAGMA) to infer relevant associations within metagenomes. MAGMA takes into account the specificities of metagenomic data and offers the possibility to take into account the effect of a structuring factor on the distribution of OTUs before looking for associations between microbes. Through participations in different metagenomics projects, I confirmed the relevance of the tool developed and identified ways of improving the current biological issues
Auffray, Thomas. « Etude des interactions chimiques entre les espèces cultivées d'Elaeis et les insectes pollinisateurs ». Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT074.
Texte intégralThe African oil palm Elaeis guineensis Jacqu. (Arecales: Arecaceae) is a tropical plant of economic interest and the world's leading source of vegetable oil. Oil production depends on pollination by weevils of the genus Elaeidobius (Coleoptera: Curculionidae). These insects are involved in a specialized mutualist relationship with the host plant: they develop at the expense of the male inflorescences they detect through the odors emitted during the anthesis, while the female inflorescences are pollinated by mimicking the male odors. E. guineensis is affected by a lethal disease in South America that leads to the development of commercial varieties of interspecific hybrids, resulting from artificial crossing between E. guineensis and the South American oil palm Elaeis oleifera (Knuth) Cortés. However, the natural pollination of these hybrids is inadequate and require the intervention of a costly assisted pollination. This thesis hypothesizes that the chemical communication underlying the successful encountering between each oil palm species and their respective pollinators is deficient in hybrid palms.The main objective of this work was to study the functioning of the pollination system for both oil palm species to understand why natural pollination in hybrids is inefficient. The study was conducted in a commercial plantation in Ecuador, including the two species E. guineensis and E. oleifera present with their respective pollinating insects, the African weevil Elaeidobius kamerunicus Faust. and the South American weevil Grasidius hybridus O'Brien & Beserra (Coleoptera: Curculionidae), as well as interspecific hybrid palms. Using techniques of trapping and sampling of floral odors, our results showed the pollination system of both species of palm is based on the emission of a specific chemical signal and an olfactory deception, reinforced by a phenomenon of thermogenesis. The two insects are attracted in a small proportion to hybrid palms, which have an intermediate chemical composition compare to parent species. Physiological and behavioral tests permit the identification of the key volatile organic compounds responsible for pollinator attraction.This work should contribute to theoretical knowledge about the oil palm pollination system and the development of practical methods for pollinator management to reduce costs in assisted pollination
Martino, Aurelia. « Écologie trophique des poissons top-prédateurs - interactions entre espèces natives et introduites au sein d'écosystèmes dulçaquicoles ». Phd thesis, Université Paul Sabatier - Toulouse III, 2012. http://tel.archives-ouvertes.fr/tel-00763302.
Texte intégralMartino, Aurélia. « Écologie trophique des poissons top-prédateurs, interactions entre espèces natives et introduites au sein d'écosystèmes dulçaquicoles ». Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1773/.
Texte intégralThe impacts of exotic species on ecosystem functions are still poorly known. Top-predatory fish, which are at the top of the food-chain are relevant models to study the impacts on freshwater ecosystems. Introductions of exotic top-predator fish can induce changes in the functioning of freshwater communities, that could be inferred by stable isotope analyses in lentic and lotic food-webs, using trophic positions and diet compositions of top-predators. Moreover, the otolith chemical signatures can discriminate freshwater fish stocks and help to reconstruction of the introduced fish life history. Our results provide new information about trophic ecology of top-predator fish, and this knowledge will be useful to design regional conservation plans
Siou, Dorothée. « Développement épidémique de la fusariose des épis de blé et conséquences des intéractions entre espèces du complexe fusarien ». Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00849969.
Texte intégralFayaud, Benoit. « Déterminants de la croissance précoce et impact sur les interactions entre espèces dans les associations de cultures à base de légumineuses ». Phd thesis, Université d'Angers, 2012. http://tel.archives-ouvertes.fr/tel-00997180.
Texte intégralLiancourt, Pierre. « Stratégies fonctionnelles et interactions entre espèces dominantes le long de gradients de ressources hydrique et trophique au niveau des pelouses calcaires ». Université Joseph Fourier (Grenoble), 2005. http://www.theses.fr/2005GRE10064.
Texte intégralThe three grasses Bromus erectus, Brachypodium rupestre and Arrhenatherum elatius dominant xeric and nutrient poor, mesic and nutrient poor, and mesic and nutrient rich gras si and respectively. We hypothesized that three contrasting strategies may explain this pattern, depending on water and nutrient availability. Resource conservation strategy may be associated to nutrient poor communities whereas resource exploitation may be associated to nutrient rich community. On the other hand, the two dominant grasses of mesic communities Brachypodium rupestre and Arrhenatherum elatius may have a strong competitive ablhty but not Bromus erectus. This former species may rather dominate thanks to higher tolerance ability to abiotic constraint (i. E. Drought). Ln order to test these hypotheses, we manipulated water, nutrients and biotic interactions separately on the three grasses in a pots experiment and on the three dominant grasses and their communities on the field. Leaf traits and target response without any biotic interactions are consistent with our hypothesis as we confirmed the highest drought tolerance ability of Bromus erectus and the best conservative strategy ofboth B. Erectus and B. Rupestre. Competition experiment showed that there is a ranking in competitive response on the field, and this ranking is stable whatever the resource availability. B. Erectus was the most affected by competition, B. Rupestre was intermediate and A. Elatius was the least. Most importantly, the three asses showed. Contrasted competitive effect. The large conservative species B. Rupestre had a much higher competitive effect than the short conservative and drought tolerant B. Erectus, which may explain their dominance in mesic and xeric sites respectively. However, our results suggest that the competitive effect of B. Rupestre may involve primarily interference mechanisms and likely allelopathy, as compared to the resources competition processes of the exploitative A. Elatius
Zarzoso-Lacoste, Diane. « Vers une meilleure compréhension des interactions trophiques directes et indirectes entre prédateurs invasifs et espèces natives au sein des écosystèmes insulaires ». Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4330/document.
Texte intégralIntroduced predators, particularly cats (Felis silvestris catus) and rats (Rattus spp) are recognized as a major factor of rarefaction and extinction of island bird species. The impact of predation on bird populations is usually assessed through the morphological identification of bird remains in predator diet samples. A review conducted in this thesis highlighted the qualitative and quantitative biases related to the difficulty of detecting and identifying the consumed bird species in predator diet samples. Molecular methods allow the accurate detection and identification of targeted prey DNA in the diet of predators. A large part of the work entailed here has been to optimize the molecular protocol and particularly the key steps of the selection of.taxon-specific primer pairs and the extraction of prey DNA. A comparative study of the performances of both morphological and molecular methods highlighted the strength of the latter in the detection and identification of the bird species preyed by cats and rats on Niau island (French Polynesia). The study of the direct (predation) and indirect (competition for food) trophic interactions between three invasive predators (R. exulans, R. rattus and F. s. catus) and a critically endangered bird, the Tuamotu Kingfisher (Todiramphus gambieiri), demonstrated a very low impact of cats and rats on the population of Tuamotu Kingfisher through predation, but a high potential for food competition between this bird and the two species of rats, particularly for lizards (Scincidae) and some terrestrial arthropods. Finally, management perspectives regarding the conservation of Kingfisher Gambier are proposed and discussed
Dommanget, Fanny. « Interactions entre espèces invasives et communautés végétales des berges de cours d’eau : vers l’utilisation du génie écologique dans la lutte contre les Renouées asiatiques ». Thesis, Montpellier, SupAgro, 2014. http://www.theses.fr/2014NSAM0004/document.
Texte intégralTraditional methods for the management of Asian knotweeds (Fallopia spp.), among the worst invasive plants worldwide, are fastidious and expensive. Managers try to develop alternative technics such as bioengineering. Habitually used for riverbank protection against erosion, bioengineering also promotes the rapid recovery of plant communities. One issue for the control of Asian knotweeds is to improve such methods in order to restore competitive plant communities able to regulate the invasive populations. In this context, this work aims at better understanding the role of biotic interactions in the regulation of Asian knotweed populations. In this PhD project, we focused on Asian knotweed populations already established, trying to highlight factors that control their performance. Asian knotweeds are rare in mature and structured forests and are known as pioneer species in their native range. Our hypothesis is that competition and particularly competition for light, has a central role in the control of their performance. The objective of this work was to test this hypothesis through i) the evaluation of the role of light in the performance of Asian knotweeds (chapter 1), ii) the study of the role of competitive interactions (chapter 2) and iii) the investigation on the inhibitory effect of Asian knotweed on Salicaceae cuttings in different light conditions (chapter 3). The first chapter highlights, through field measurements, the importance of light quantity filtered by plant canopy relatively to other factors like disturbance and soil resources on aerial biomass production (part 1). Another experiment in semi-controlled conditions, where Asian knotweeds were grown under a light gradient, shows their phenotypic plasticity and puts forward different light thresholds considering biomass production, resource allocation or capacity to filter light.The second chapter focuses more specifically on biotic interactions like competition for light. The first part demonstrates, through the field evaluation of knotweed performance along environmental gradients, the major role of the functional structure of plant community. The second part studies more precisely the respective competitive effects between Salix viminalis (a good candidate for the control of Asian knotweeds) and Asian knotweed. Finally, the last chapter deals with allelopathic effect of Asian knotweed on cuttings of different Salicaceae species. A first analysis shows differential inhibitory effects between Salicaceae species (part 1). A second analysis repeats the first one in different light conditions and highlights resource trade-offs in Asian knotweed which favors light acquisition to secondary compound production. This PhD thesis, at the crossing point of invasion ecology, community ecology and functional ecology, is focused on the highly invasive Asian knotweeds. This work proposes new insights on their ecology allowing a better understanding of their invasive capacities in order to improve their management
Tremblay, Serge. « Impact du meunier noir (Catostomus commersoni lacepede) sur les populations d'ombles de fontaine (Salvelinus fontinalis Mitchill) : dynamique des interactions entre deux espèces taxinomiquement distantes ». Thèse, Université du Québec à Trois-Rivières, 1987. http://depot-e.uqtr.ca/5880/1/000567490.pdf.
Texte intégralHamani, Vincent. « Vers une meilleure compréhension des écosystèmes portuaires : interactions entre les organismes filtreurs et leur environnement ». Thesis, La Rochelle, 2022. http://www.theses.fr/2022LAROS013.
Texte intégralThe hyper-anthropization, particularly along our coasts, has profoundly modified the environment. New structures, such as harbors, emerging, forming “true” ecosystems. Among the multitude of species inhabiting the port, one group seems particularly interesting to study: the filter feeders (bivalves and tunicat). These organisms have a strong interaction with the port environment due to their behaviour. Indeed, by remaining anchored to the structures, they are constantly subjected to the environmental factors that characterize the port and their feeding behavior, the filtration, leads them to be in contact with a large quantity of water and therefore with the elements that are in it. The objective of this thesis is to study this particular socio-ecosystem that is the port environment through this key group: the filter feeders. Through a multidisciplinary approach, this work, has allowed :-to study and map the communities of filter feeders present in the marina of La Rochelle; showing the complexity of their community and the fact that they are impacted by anthropogenic and hydrosedimentary factors.-to analyze the effect of two common contaminants in the port environment, copper and zinc, on the metabolism of a model filter-feeder organism : the scallop (Mimachlamys varia); and to show that they impacted several metabolic pathways involved in numerous biological functions, such as osmoregulation, oxidative stress, energetic metabolism, reproduction and apoptosis.- to highlight the fact that filter feeders are involved in the composition of the mud by remobilizing the sediments present in the water column and by modifying their physico-chemical properties; and that is species dependent and is strongly modulated by environmental conditions such as the level of organic matter.- to develop several innovative sampling and analysis methods needed to understand this particular environment
Kaba, Oumar Barou. « Étude des mécanismes et microprocessus régissant les interactions entre les espèces minérales et les modulateurs de flottation en vue de la valorisation des minerais de phosphates complexes ». Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0038.
Texte intégralBecause of the depletion of high grade phosphate deposits, usually associated with silicate gangue minerals, which are easy to treat by grinding/classification and/or by flotation, the industry has to rely more on carbonate gangue phosphate ores which are more abundant but more difficult to beneficiate by flotation. Most of the minerals contained in these phosphate ores are semi soluble, which results in a similar chemistry of their surface and a poor separation by flotation between the phosphate minerals such as apatite (calcium phosphate) and the gangue minerals such as calcite (calcium carbonate). The reverse flotation method in acid medium has been found to produce a better contrast of separation between calcite and apatite. This method relies on the addition of an acid such as phosphoric acid which acts as a selective depressant of apatite. However, the mechanisms governing this mineral separation and in particular the reactions occurring at the surface of these minerals are not very well understood. The objective of this thesis is to study the reactivity of calcite and apatite in aqueous solution as a function of phosphoric acid concentration and reaction time. For this, several analytical techniques (Raman, infrared and X-ray photoelectron spectroscopies, and X-ray diffraction and scanning electron microscopy) are used to measure the nature of the species adsorbed or formed at the surface of calcite and apatite. In particular, with Raman spectroscopy it was possible to measure directly in-situ the changes occurring in solution and at the mineral surface in the presence of phosphoric acid, which should eliminate any possible artefact caused by the drying of the samples when using the other analytical techniques. The first major result was on the reactivity of the two minerals measured after 15 min of contact with an acid solution reveals the phenomenon of passivation of the surface deduced from the variation of the consumption of the protons with the concentration of acid. Indeed, all the in-situ and ex-situ analytical techniques used in this study have shown the presence of calcium phosphate (brushite) on calcite and of calcium carbonate on apatite after contact with phosphoric acid, and with a concentration which increases with acid concentration. Moreover, the acid concentration for the onset of detection of calcium phosphate on calcite and for the start of passivation (decrease in acid consumption) coincides, which implies that the presence of calcium phosphate is responsible for the passivation. For apatite, although the acid concentration for the onset of detection of calcium carbonate on apatite and for the start of passivation coincides, calcium carbonate was removed at higher phosphoric acid concentrations. However, kinetic in-situ studies using Raman spectroscopy performed at several phosphoric acid concentrations and at a fixed pH of 4.5 all confirmed the presence of calcium carbonate on apatite but also revealed that a new phase of calcium phosphate was also present after only 2 min of contact with phosphoric acid and its concentration increased with contact time. Surprisingly, the presence of calcium phosphate and its growth on apatite were transient, lasting 5-6 min before quickly vanishing and then reappearing again for several cycles. These cycles of calcium phosphate growth and disappearance on apatite may be the result of precipitation of calcium phosphate followed by their removal in the chemical and / or mechanical conditions. Similar kinetic in-situ studies of calcite using Raman spectroscopy under the same conditions as with apatite confirmed the presence of calcium phosphate (brushite) on calcite but only after 4 minutes of contact with phosphoric acid, indicating a slower kinetic of calcium phosphate formation than on apatite [...]
Flacher, Floriane. « Influence des interactions entre espèces végétales sur les relations plantes-pollinisateurs : cas de la compétition induite par la présence d'espèces anémophiles sur l'attractivité aux pollinisateurs d'espèces entomophiles ». Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066017/document.
Texte intégralAttractiveness traits of insect-pollinated plants to pollinators (i.e. flowers and associated rewards) can be sensitive to variations of resources (e.g. nitrogen, phosphorous). As competition between plants can modify resource availability, we studied its effect on insect-pollinated plants and their floral traits involved in attractiveness to pollinators, especially in presence of wind-pollinated plants. We showed that the presence of a competitive wind-pollinated species could reduce total flower production, floral display size and total sucrose allocated to nectar of insect-pollinated species. Especially, the stronger the competitor, the stronger is the effect on floral traits. The study of wild pollinators’ visits on an insect-pollinated plant in competition with a wind-pollinated plant revealed a decrease in the number of visits associated to the decrease of floral display size and total flower production. Therefore, even though they do not interact directly with pollinators, wind-pollinated plant species can modulate plant-pollinator interactions through competitive interactions. This thesis raises new perspectives for the study of plant-pollinator networks, which are generally focused on insect-pollinated plants, by opening them up to the whole plant community
Jaubert, Jean. « Etudes de quelques interactions entre espèces et facteurs de l'environnement (lumière, température et oxygène dissous) mesures in situ en milieu récifal : conception et réalisation d'instruments de mesure et protocoles expérimentaux ». Nice, 1987. http://www.theses.fr/1987NICE4110.
Texte intégralFraga-Beddiar, Arifa. « Interactions entre les symbiotes mycorhiziens et les symbiotes fixateurs d'azote chez l'aulne glutineux (alnus glutinosa L. Gaertin) ». Nancy 1, 1987. http://www.theses.fr/1987NAN10335.
Texte intégralBlanchard, Fabian. « Effets de l'exploitation par pêche sur la dynamique de diversité des peuplements de poissons démersaux : analyse comparée du rôle des interactions entre espèces dans le golfe de Gascogne et dans le golfe du Lion ». Brest, 2000. http://www.theses.fr/2000BRES2027.
Texte intégralLiarsou, Alexandra. « Contribution de l'archéologie à la réflexion sur le partage entre nature et culture et mise en perspective des stratégies de gestion de la "biodiversité" : analyse de quelques interactions de l'espèce humaine avec d'autres espèces animales sur la très longue durée ». Paris 1, 2012. http://www.theses.fr/2012PA010516.
Texte intégralAubree, Flora. « Adaptation dans un monde en mouvement - adaptation des communautés et relations biodiversité-fonctionnement des écosystèmes, hétérogénéité spatiale et évolution de la tolérance au stress, migration pulsée et adaptation locale ». Electronic Thesis or Diss., Université Côte d'Azur, 2021. http://www.theses.fr/2021COAZ6023.
Texte intégralThe world is changing at an unprecedented rate in many interconnected aspects, and ecosystems are primarily concerned. The current shift in environmental conditions is accompanied by an increase in the temporal variability of environmental processes, which is also driven by anthropogenic activities. This work is part of the effort to understand how variability in key environmental processes impacts ecosystem composition and ecological and evolutionary functioning at different scales. The focus is made in particular on the interplay between such variability and the process of adaptation, which is a key aspect of ecosystem dynamics. Adaptation is integral to the functioning of ecosystems, yet it is still relatively little considered. In this thesis, three biological scales are considered – the scale of the community, the scale of the species, and the scale of populations. A theoretical modeling approach is used to introduce some aspects of variability and investigate how ecological and evolutionary dynamics are impacted.At the community scale, the impact that changes in the species co-adaptation level may have on some biodiversity-ecosystem functioning (BEF) relationships (diversity-productivity, diversity-stability and diversity-response to invasion relationships) is questioned. Random and co-adapted communities are compared using adaptive dynamics methods. Results show that species co-adaptation impacts most BEF relationships, sometimes inverting the slope of the relationship. At the species scale, the evolution of stress tolerance under a tolerance-fecundity trade-off model is explored using adaptive dynamics as well. The evolutionary outcomes are determined under different trade-offs and different stress distributions. The most critical parameters in determining the evolutionary outcomes (ESS trait value, branching) are highlighted, and they evidence that stress level heterogeneity is more critical than average stress level. At the population scale, gene flow between sub-populations of the same species is an important determinant of evolutionary dynamics. The impact that temporally variable migration patterns have on gene flow and local adaptation is questioned using both mathematical analyses and stochastic simulations of a mainland-island model. In this model, migration occurs as recurrent “pulses”. This migration pulsedness is found to not only decrease, but also increase, the effective migration rate, depending on the type of selection. Overall, migration pulsedness favors the fixation of deleterious alleles and increases maladaptation. Results also suggest that pulsed migration may leave a detectable signature across genomes. To conclude, these results are put into perspective, and elements are proposed for possible tests of the predictions with observational data. Some practical consequences they may have for ecosystem management and biological conservation are also discussed
Germain, Karine. « Les infections à lentivirus chez la chèvre et le mouton : étude des interactions entre sous-type viral et espèce animale ». Poitiers, 2007. http://www.theses.fr/2007POIT2267.
Texte intégralThe small ruminant lentiviruses (SRLV) display a high genetic diversity and are currently classified into several groups, and an increasing number of subtypes. While a high prevalence of SRLV infection has been reported in sheep and goats from France, the prevalent SRLV strains circulating in this country are still poorly known. In this study, a large-scale screening method (HMA) based on the sequences of gag and env genes has been developed for monitoring the genetic evolution of SRLV. Molecular epidemiological surveys in sheep and goats flocks from southern of France revealed a high prevalence of subtypes B1 and B2. Interspecies transmission of both subtypes was reported in mixed flocks, as well as co-infection and recombination. However, subtypes B1 and B2 were found with different frequencies in sheep and goats, suggesting a differential adaptation of SRLV subtypes in these hosts. The biological properties of two field SRLV isolates belonging to subtypes B1 and B2 were compared in vitro using different cell types, and in vivo in sheep and goats experimentally infected by intratracheal inoculation. These strains share similar phenotype but exhibit different replicative properties in macrophages and synovial membrane cells. The subtype B1 virus has been shown to be particularly prone to infect goats, compared to sheep. While the subtype B2 virus infects sheep and goats with the same efficiency, viral expression is more frequently detected in sheep than in goats. These results confirm those obtained from field investigations showing specific interaction between SRLV subtypes and their natural hosts
Fontaine, Alain. « Interaction entre une onde acoustique et un fluide : application à la thermoacoustique et à la séparation des constituants d'un mélange binaire par onde ultrasonore ». Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1949/.
Texte intégralIn the present work, we study the interaction between an acoustic wave and a compressible and incompressible fluid. In the first part, we present the numerical study of a thermoacoustic refrigerator and more particularly the influence of the gas state equation on the thermoacoustic effect. Thermoacoustic heat pumping is a complex phenomenon which leads to a hydrodynamic heat flux in the thermal boundary layer near a porous medium, due to acoustic waves. The second part deals with the influence of acoustic streaming on species separation of a binary mixture in a shallow cavity cell subjected to temperature gradient and under microgravity. The unicellular flow inducted by the streaming may lead to significant species separation. Analytical results are corroborated by direct numerical simulations. Then, a linear stability analysis of the unicellular flow is performed
Kong, Heng. « Variations spatio-temporelles de la structure taxonomique et la compétition alimentaire des poissons du lac Tonlé Sap, Cambodge ». Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30122/document.
Texte intégralThe Tonle Sap Lake (TSL), Cambodia, is a flood-pulse system. It is the largest natural lake in South- East Asia and constitutes one of the largest fisheries over the world, supporting the livelihood 2.5 million peoples. Seasonal change in annual hydrological cycle appears to have influence on fish community structure, both spatial and temporal variation, particularly on feeding behavior of TSL's fishes. Nonetheless, the Mekong River Basin is changing rapidly due to accelerating water infrastructure development (hydropower, irrigation, flood control, and water supply) and climate change, bringing considerable modifications to the annual flood-pulse of the TSL. Such modifications are expected to have strong impacts on fish biodiversity, abundance, reduced habitat and food availability within the lake. To invest how TSL's fish community structure responds to the seasonal change, how they shift their diet across hydrological cycles and feeding competing for food resource: First, we aim to characterize the spatio-temporal variations of fish taxonomic composition and to highlights the underlying determinants of these variations. For this purpose, we estimated beta diversity as the total variance of the site-by-species community matrix and partitioned it into Local Contribution to Beta Diversity (LCBD) and Species Contribution to Beta Diversity (SCBD). We then performed multiple linear regressions to determine whether species richness, species abundances and water level explained the temporal variation in the contribution of site and species to beta diversity. Our results indicate strong temporal variation of beta diversity due to differential contributions of sites and species to the spatial variation of fish taxonomic composition. We further found that the direction, the shape and the relative effect of species richness, abundances and water level on temporal variation in LCBD and SCBD values greatly varied among sites, thus suggesting spatial variation in the processes leading to temporal variation in community composition. Overall, our results suggest that fish taxonomic composition is not homogeneously distributed over space and time and is likely to be impacted in the future if the flood-pulse dynamic of the system is altered by human activities. Second, we aim to investigate the temporal pattern of the most occurrence and abundance species and how their co-occurrence pattern across hydrological cycles. We found that occurrence and abundance patterns were temporally varied at all water level seasons. Strong temporal variation in species occurrence was occurred with visiting species such as Labiobarbus leptocheilus and Poropuntius deauratus while water level starts to fill into the TSL. We further observed that the abundance of 17 species was strongly varied while other 22 species (mainly TSL's residential species) were stable within the year. Positive species co-occurrence pattern was generally higher than negative species co-occurrence at all water level seasons. Highest positive co-occurrence patterns were found during the period of decrease and low water level seasons while fishes are migrating from flooded areas, competing for resource and habitats during low water season. Study on temporal distribution and species co-occurrence of fish and how community responds to the seasonal change in hydrological cycles provides critical information for fisheries management and conservation in the Tonle Sap Lake (TSL) as well as maintaining fish biodiversity in the Mekong system. Third, the implications of seasonality on food web structure have been notoriously understudied in empirical ecology, particularly in TSL's system. The current study, we focus on seasonal changes in one key attribute of a food web, vertical trophic position of consumers
Zidat, Timothée. « Communication chimique chez un mammifère social et monogame : rôle dans la sélection sexuelle et les relations entre groupes ? » Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1072.
Texte intégralChemical communication (or olfaction) is the most common form of communication in the animal kingdom and plays an essential role in mediating social and reproductive behaviour. During my Ph.D. thesis, I study the role of chemical communication in a social species, the Alpine marmot (Marmota marmota). I was first interested in the role of olfaction in sexual selection context. The Alpine marmot is a cooperative breeder and only the dominant pair access to the reproduction, generating an intense intra-sexual competition for access to reproduction. By analysing anal gland secretions of 154 individuals with gas chromatography and mass spectrometry, I found that anal gland secretions could inform on sexual maturity, social status and sex. This information may be involved in intra-sexual competition in this species. Furthermore, although being a socially monogamous species, extra-pair paternity occurs in the Alpine marmot. Females choose males with an optimal genetic compatibility (relatedness and genotype to the Major Histocompatibility Complex). By analysing anal gland secretions of 63 sexually mature marmots, I found a significant concordance between chemical distance and relatedness, allowing females to assess the genetic compatibility of the potential partners. Finally, the Alpine marmot as being a territorial species, I was interested in the role of olfaction in relations between groups. For this, I tested the "dear enemy" hypothesis and I highlighted that any stranger to the social group is considered as an enemy of the group. To conclude, chemical communication plays an essential role in social and reproductive interactions in social species
Grossiord, Charlotte. « Impact of tree species diversity on water and carbon relations in European forests ». Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0155/document.
Texte intégralBiodiversity is known to support and boost a wide range of forest ecosystem functions and services like productivity and resistance against insect pests and diseases. However, whether tree species diversity also promotes water and carbon acquisition and use in forest ecosystems is still unclear. Furthermore, in the current context of global warming, information on how tree species diversity can influence the response of forest ecosystems to extreme climatic events such as drought are urgently needed. In this framework, the objective of my PhD thesis was to determine how tree species diversity influences important functions of the water and carbon cycle including transpiration, carbon isotope composition and water extraction depth at the tree- and ecosystem-Scale under contrasting soil water conditions. My work was conducted within the FunDivEUROPE project in a network of permanent forest stands and tree plantations across a North-South gradient in Europecovering a wide range of climatic conditions. I found considerable variability among species or forest types in the response of transpiration and carbon isotope composition at the tree- and ecosystem-Scale across Europe. Species diversity did not affect the water and carbon relations of tree species and forest ecosystems under non-Limiting soil water conditions. However, a strong effect of species diversity was observed under drought conditions in some forest types. Based on these data, I discuss the potential mechanisms of species interactions that may explain the observed patterns. I also point out that the influence of species diversity is highly context-Dependent, and changes with local environmental and climatic conditions. In terms of forest management applications, I suggest that, at least in some regions, controlling for tree species diversity along with stand density and total basal area could be recommended to help forests adapt to drier conditions
Pérot, Thomas. « Quel est le niveau de détail pertinent pour modéliser la croissance d'une forêt mélangée ? Comparaison d'une famille de modèles et application aux peuplements mélangés chêne sessile - pin sylvestre ». Phd thesis, AgroParisTech, 2009. http://tel.archives-ouvertes.fr/tel-00432573.
Texte intégralSainte-Marie, Guillaume. « Interactions entre le peuplier faux-tremble et l'épinette noire en forêt boréale de l'ouest du Québec ». Mémoire, 2009. http://www.archipel.uqam.ca/2613/1/M11228.pdf.
Texte intégralMaezo, María José. « Interaction entre deux espèces envahissantes : l'écrevisse à taches rouges et le myriophylle à épis ». Mémoire, 2008. http://www.archipel.uqam.ca/1687/1/M10628.pdf.
Texte intégralMarselli, Geoffrey. « Réponses des espèces de poissons à des facteurs de stress environnementaux dans la région des Grands Lacs de l'Ontario ». Thèse, 2020. http://depot-e.uqtr.ca/id/eprint/9734/1/eprint9734.pdf.
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