Dissertationen zum Thema „Interactions des 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.
Der volle Inhalt der QuellePlantations 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.
Der volle Inhalt der QuelleCazelles, Kévin. „Influence des interactions biotiques sur la répartition gégographique des espèces“. Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT122.
Der volle Inhalt der QuelleOne of the most pressing challenges currently in the field of biogeography is the successful integration of ecological interactions in species distribution models. Although the scientific literature points out the evidence of the controlling role interactions play on local community structure, relatively few studies have demonstrated its importance over large geographical gradients. Developing a concise, clear explanation for this issue remains a significant challenge that biogeographers need to answer. The main issue associated to the lack of a clear answer concerning the role of interactions at broad spatial scales is that most of scenarios of biodiversity changes assume that interactions can be ignored. When tested, if this hypothesis is proven false, then a re-consideration of species distribution models and their development must be undertaken to include relationships among species. I begin this thesis with a theoretical investigation on this topic, where classical theories have typically ignored ecological interactions. In the first chapter of the thesis I present the integration of interaction networks into a theoretical model of species distribution coming from one of the most important theory in biogeography: the theory of island biogeography. This work shows how together the biotic and abiotic factors can affect the expectations derived from the classical theory. Building upon the findings in the first chapter, in the second chapter, I show how interactions can affect co-occurrence (between species) data. Such data contains the presence or absence of several species for a similar set of sites dispersed along large latitudinal gradients. Using a probabilistic model, I obtain theoretical results linking co-occurrence data and the information included in ecological networks. I clearly demonstrate that interactions shape co-occurrence data. Furthermore, I show that the higher the number of links between two species, the more difficult it is to detect their indirect interaction. Similarly, if a species experiences many interactions, it is then challenging to detect any sign of interactions in co-occurrence data for this species.In the third chapter of the thesis, I assess five sets of co-occurrence data, which had descriptions of their interactions available. Using this data, I was able to confirm my hypotheses put forth in my second chapter, by showing that species co-occur differently from non-interacting one. These results also point out that the abundance of interaction must preclude their detection in co-occurrence data. However, when accounting for abiotic similarities among sites, signals of interactions are weakened. Therefore, my results suggest that using abiotic factors to infer co-occurrence probabilities capture a part of the link between species and further pinpoint the uncertainty associated to this part. As a result of these findings, the predictive power of classical species distribution models used to date is brought into question. My research findings bring new theoretical elements to the forefront when considering the influence of ecological interactions and how they shape species geographical distributions, while also introducing an original methodology for studying species co-occurrence: examining them in the light of ecological networks. Before concluding, my fourth and final chapter, I propose a promising new avenue to further investigate integrating species interactions in biogeography. Here, I introduce interactions in terms of energetic constraints, which will provide a sound basis for a metabolic theory of biogeography
Monmeyran, 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.
Der volle Inhalt der QuelleDuring 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.
Der volle Inhalt der QuelleHigh 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.
Der volle Inhalt der QuelleThe 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
Bourdier, Thomas. „Hétérogénéité des peuplements forestiers et production : interactions avec les traits fonctionnels des espèces“. Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAV050/document.
Der volle Inhalt der QuelleUnderstanding the link between diversity ecosystem functioning has been a major topic of ecology for the last decades. When studying the relationship between diversity and productivity in tree populations and communities, size heterogeneity has often been disregarded. Our study focuses on the effect of size heterogeneity on the production of pure and mixed forest stands as wells its interactions with species’ functional traits. By using national forest inventory data, we were able to demonstrate a negative effect of size heterogeneity in both pure and mixed stands. In the latter case, we showed a positive effect of species richness as well as a positive effect of a decrease of shade tolerance with tree size, i.e. when the less tolerant species are dominant in the overstorey. We propose potential mechanisms to explain our results and discuss the consequences of such findings at larger time scale for the stability and resilience of forest stands
Baillard, Vincent. „Modélisation de distribution de sensibilité des espèces pour la protection des communautés“. Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0065.
Der volle Inhalt der QuelleHuman activities have numerous effects on ecosystems. They can for example result in spillage or leakage of contaminants in ecosystems as during spreading of pesticides in agricultural lands. Environmental risk assessment allows to characterize those effects to maintain them at a level considered acceptable. This assessment is usually based on monospecific bioassays, but concentration-response relationships thus described can then be included in Species Sensitivity Distributions (SSD). Those SSD, widely used in environmental risk assessment, then allows to define a concentration that only have an effect on a small fraction of the species found in an ecosystem (usually 5%, leading to hazardous concentrations for 5% of species). One of the most important problems of this kind of approaches is that it still lacks environmental relevance. Monospecific bioassays indeed providing the information to model SSD are usually realised in non realist conditions (organisms isolated and thus not subject to biotic interactions, experimental conditions far from environmental reality, obtention of a unique sensitivity value for a species whereas this sensibility can be variable from one population to another...). This lack of realism is compensated by the application of an assessment factor which divides the final value by a value that increases as the realised estimation is distant from environmental reality, thus giving lower values that are considered more protectives. The work presented here sought to integrate (i) the effect of intraspecific variability on SSD curves parameters, in particular on hazardous concentrations for 5% of species and (ii) the combined effect of an herbicide and interspecific competition on the vegetal communities that are grass stripes following several modeling approaches for each data processing step. Results show the importance of the integration of all this biological complexity in environmental risk assessment procedures as well as the risk of underestimation of assessment factors usually applied on results from SSD modeling
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.
Der volle Inhalt der QuelleMartino, 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/.
Der volle Inhalt der QuelleThe 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
Jorissen, Hendrikje. „Comprendre l’association algue coralline – corail : des espèces clés aux médiateurs chimiques et microbiens“. Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLP025.
Der volle Inhalt der QuelleCrustose coralline algae (CCA) are commonly associated with healthy reefs and play an important role in benthic systems by guiding settlement of many habitat forming or ecologically important organisms, including corals. However, the ability of CCA to induce coral settlement is not ubiquitous among CCA species. Corals exhibit settlement preferences for certain CCA species. These preferences demonstrate the capacity of coral larvae to discriminate among CCA species and raise the question of the mechanisms involved. Despite the enormous variety of CCA species on coral reefs, little is known about the diversity of their associated chemicals and microbes and the ecological role of these compartments, notably for coral recruitment. Chapter 2 of this thesis investigated the microbial and chemical composition of six CCA species, which occupy different ecological niches on the coral reefs of Moorea (French Polynesia), and how these two compartments (i.e., microbial and chemical) relate to successful settlement success of Acropora cytherea larvae. Results showed settlement was highest on the cryptic CCA species Titanoderma prototypum and that practically no larvae settled on exposed CCA species. While all CCA species had distinct metabolic fingerprints and contained high metabolic diversity, the metabolomic diversity and richness of T. prototypum were significantly higher than those of the other CCA species. T. prototypum also hosted a significantly higher bacterial diversity than the other CCA species, and contained a higher abundance of bacteria that potentially produce antibacterial compounds. The presence of these bacteria could inhibit coral pathogens, which in turn could enhance the survival of coral settlers. Thus, coral settlement is a complex process of biochemical communications between CCA, their associated microbial surface communities and coral larvae. Despite widespread acceptance that CCA positively influence coral recruitment success, there are no experimental data on the effects of CCA species on late post-settlement survival and growth of corals. Chapter 3 tested the impact of four CCA species from two habitats (exposed and subcryptic) on the survival and growth of Pocillopora recruits. CCA had a contrasting effect on the survival of coral recruits depending on habitat and recruit size. In subcryptic habitats, CCA can reduce the survival and/or growth of coral recruits via direct competitive overgrowth, while, in exposed habitats, they can enhance coral recruitment by alleviating competition with turf algae. Importantly, this study demonstrated that not all CCA species are beneficial to the survival and growth of coral recruits and that there is considerable variability in both the outcome and process of competition between CCA and corals. Chapter 4 and 5 focused on investigating whether two environmental stressors, ocean acidification (OA) and hypoxia, respectively, impact the coral-CCA association by disrupting larval settlement behavior and recruitment of two coral species (A. cytherea and A. pulchra) on an otherwise preferred and beneficial CCA species (T. prototypum). Larvae of both coral species avoided bottom exploration and settlement in low pH environments. They avoided bottom exploration in reduced oxygen environments and settled on T. prototypum fragments only in oxygen rich environments, with settlement rates increasing exponentially with oxygen concentrations. These results indicate that low oxygen and low pH areas can negatively influence coral settlement success and that oxygen and pH act as chemical cues for coral larval orientation and settlement. This thesis aids to better understand the role of CCA, micro-organisms and chemicals in the fine-scale dynamics of coral recruitment now and under future ocean conditions. It highlights that CCA-coral interactions are complex processes that are likely mediated by chemicals and microbes and these interactions can be affected by changing environments
Fayolle, Adeline. „Structure des communautés de plantes herbacées sur les Grands Causses : stratégies fonctionnelles des espèces et interactions interspecifiques“. Montpellier SupAgro, 2009. http://www.theses.fr/2009NSAM0013.
Der volle Inhalt der QuelleGoetghebuer, Lise. „Les communautés bactériennes de rivières: étude de la dynamique des espèces au sein d’une communauté modèle“. Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/279062.
Der volle Inhalt der QuelleDoctorat en Sciences agronomiques et ingénierie biologique
info:eu-repo/semantics/nonPublished
Mulier, Chloé. „Vers une gestion in situ des diversités biologiques“. Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTD057/document.
Der volle Inhalt der QuelleBiological diversity constitutes one of the major pattern of ecosystem functioning, and a potential for adaptation and evolution of life in the context of climate change. As species are in many ways tightly interconnected, biodiversity loss can trigger large cascade effects and might lead to largely unpredictable consequences, reaching far beyond the visible reduction in the number or distribution of species. The high complexity of ecological organization is often a nightmare for decision-making, starting from accurately measuring biodiversity. This is however a necessary step to take if we want to prioritize action in biodiversity management, in order to preserve as much diversity as possible under limited resources. Though this thesis does not pretend to provide complete answers to those quite complex issues, it provides some reflection points for biodiversity management. It is composed of four chapters. The first chapter raises the issue of dealing with a mixed biodiversity, in which invasive species can be guests. It highlights the interconnections between the severity of the impacts of biological invasions and the contexts in which this invasion occurs. Considering invasion impacts as inherently ''ambivalent'' - i.e. good, bad or neutral for the system in which it arrives - we propose a typology to assess ambivalence in impact, based on the identification of potential sources of impact variability. For the second chapter, we focus on the measurement of biodiversity when accounting for species interactions, which we incorporates into the Noah's Arch problem developed by Weitzman (1998). We then derive a general model for ranking in situ conservation projects. We show firstly that, when accounting for ecological interactions, the problem defined by Weitzman is still an extreme solution, and secondly, that a ranking reversal is possible and completely defined by the interaction categories. In the third chapter, we use the in situ cost-benefit framework developed in Chapter 2 to compare the outcomes of two biodiversity indices, Weitzman's and Rao's. Those two indexes combine information about species survival probability, ecological interaction and distinctiveness in a different way to measure biodiversity; We analyze simple biodiversity protection plans for each index, and disentangle the role played by the different data requirement in the rankings, in a three species ecosystem. We show that such pieces of information will come as a trade-off when considered simultaneously in the measure, and that the introduction of ecological interactions among more than two species lead to more complex conclusions. Ecological interactions thus give important additional information to determine conservation objectives. Our last chapter is an adaptation of the previously defined optimization framework for the prioritization of invasive species management. It elaborates a myopic rule to determine which invasions must be controlled in priority, taking into account relative management costs and trophic cascades impacts. We discuss the gradient of the objective function composed of a diversity function W and a utility function U, to see whether we should retain several or only a few species for management under a budget constraint
Boiché, Anatole. „Conséquences de l'introduction de deux espèces végétales aquatiques exotiques (Elodea nuttallii et Elodea canadensis) sur les interactions plantes-macroinvertébrés“. Thesis, Metz, 2010. http://www.theses.fr/2010METZ009S.
Der volle Inhalt der QuelleWe used the exotic macrophytes Elodea nuttallii and Elodea canadensis originating from North-America and introduced in France during the nineteenth century (E. canadensis) and during the 1950s (E. nuttallii). Elodea nuttallii is currently actively spreading whereas E. canadensis is now integrating most of the hydrosystems in Europe. Our main objective was to study the consequences of the invasion of E. nuttallii on the macroinvertebrate communities. We first studied the role of macrophytes as habitat with E. nuttallii and the indigenous species Ranunculus peltatus and Callitriche platycarpa in Northern Vosges streams that differ in their trophic levels. Our main result was that the trophic level had a greater influence than the plant species in the repartition of the macroinvertebrates. The macroinvertebrate community hosted by E. nuttallii was intermediate between the communities hosted by R. peltatus and C. platycarpa. Plant structural complexity appears to play a role in the repartition of the macroinvertebrates. Among the macroinvertebrates associated with the macrophytes, the gammarids have a broad generalist diet. We first validated the use of Gammarus roeseli as herbivores to assess plant palatability. Then, we measured the seasonal variations of the palatability of E. canadensis and E. nuttallii and the different evolutionary strategies that the plants had developed to invade or to integrate the ecosystems. E. canadensis allocates increased resource to defence whereas E. nuttallii allocates its resources mainly to vegetative growth
Cherif, Rachid. „Etude de l’effet de la composition de la solution interstitielle des matériaux cimentaires sur les interactions multi-espèces lors des transferts de chlorures“. Thesis, La Rochelle, 2018. http://www.theses.fr/2018LAROS002/document.
Der volle Inhalt der QuelleThe durability of the reinforced concrete structures is closely related to the composition of their materials and, particularly to their properties. This durability is characterized by indicators among which we quote the diffusion coefficient of chlorides. These ionic species penetrate through the concrete and interact with the other species present in the interstitial solution (contained in concrete pores) as well as the cementitious matrix components. In the literature, there is a lake of data describing simultaneously these ionic interactions, especially their consideration in the study or modeling the ionic transport phenomena. This work focuses on the study of multispecies interactions that occur during the chloride transfer. To this purpose, the evolution of pore solutions chemistry of hardened cement pastes manufactured with different mineral additions is investigated. This solution is extracted, before and after migration test, using a specific press and analyzed by ionic chromatography. Furthermore, the microstructure evolution of these cement pastes is characterized by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). This allows highlighting the modification caused by chloride penetration. Secondly, for the modeling of chloride transport in cement based materials, a multispecies transport model is developed. In this context, several mono and multispecies transport models, under an electrical field or not, in transitory or steady state were developed previously. The aim of this numerical study is to extend these models in order to consider the ions present in the interstitial solution and their multispecies interactions leading to the precipitation of new chloride compound and the dissolution of some hydrates. The mathematical formulation of the phenomena studied was established from the principle of mass conservation and the thermodynamic equations. Initial and boundary conditions were adopted to take into account both the chemical composition of sea water and that of pore solution. Results highlight the effect of these phenomena on the pore solution chemistry and the chloride transport
Barat, Myriam. „Interactions plante-insecte, spécialisation et invasion biologique : écologie évolutive des ajoncs (genre Ulex) et de leurs charançons spécifiques (genre Exapion) en Bretagne“. Rennes 1, 2007. http://www.theses.fr/2007REN1S011.
Der volle Inhalt der QuelleThree gorse species co-exist in Brittany (France), all of them being parasitised by seed-eating weevils. One of them, Ulex europaeus is an invasive plant. I contributed to a long-term study of Ulex europaeus. We have shown that the parasite pressure has a major impact for the plant, which can explain the areas invaded; where specific grazers are absent, it can have an increased competitive advantage. I have enlarged this study to two other gorse species that occur in Brittany: U. Gallii and U. Minor. These species flower in the autumn, and are also parasitised by weevils. I have identified these weevils by using morphological and molecular characters as Exapion lemovicinum. The life cycles and the cold hardiness of these weevils are intimately linked to the phenology of their host plant. The ecological specialisation of the weevils is therefore probably the origin of their differentiation, which could have taken place by temporal isolation by means of a process of sympatric speciation
Fernandez-Conradi, Pilar. „Diversité des arbres et résistance des forêts aux invasions biologiques : application au chataignier et son complexe de bioagresseurs exotiques, chancre (Cryphonectria parasitica) et cynips (Dryocosmus Kuriphilus)“. Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0940/document.
Der volle Inhalt der QuellePlants are the playground of a large diversity of biotic interactions between related and unrelated organisms exploiting them as common resources. The aim of this thesis was to understand how plant-insect interactions vary with fungal infection of their host plant and plant diversity. I first performed a meta-analysis to provide a theoretical background for plant-mediated effects of fungal infection on herbivorous insects. Overall, I found a negative plant-mediated effect of fungi on both insect preference and performance. However, this effect varied according to fungus lifestyle, insect feeding guild and spatial location of the interactions (local vs distant). Then I experimentally tested plant-fungus-insect tripartite interactions in the particular case of exotic bio-aggressors of the European chestnut (Castanea sativa): the Asian chestnut Gall Wasp (ACGW, Dryocosmus kuriphilus), and the fungal pathogen Cryphonectria parasitica, the causal agent of chestnut blight. I performed an observational study, in natural chestnut forest stands in Italy, where I tested how ACGW infestation rates vary with the tree species composition. I also investigated the mechanisms underlying plant diversity effects on the invasive pest, with a particular focus on its natural enemies such as insect parasitoids and endophytic fungi. ACGW infestation rates was lower in oak and ash chestnut mixtures compared to monocultures or pine-chestnut mixtures. Plot composition also influenced ACGW parasitoid community composition but not their abundances, diversity or richness. Endophytic communities of galls, described by using next generation sequencing methods, did not vary with plot composition. However, they strongly differed from surrounding leaf tissues. We thus provided evidence that plant diversity and fungal pathogens are key drivers of plant-insect interactions. Understanding how plants interact with associated insects and fungi, and mechanisms underlying plant diversity effect on these interactions, will improve our knowledge on diversity-ecosystem functioning relationships and will have practical applications for the management of native and exotic forest pests
Fayaud, 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.
Der volle Inhalt der QuelleBaraud, Isabelle. „Interactions sociales et modalités sensorielles (vocale et visuelle) impliquées, chez deux espèces de mangabés (Cercocebus torquatus torquatus et Lophocebus albigena albigena)“. Rennes 1, 2007. http://www.theses.fr/2007REN1S138.
Der volle Inhalt der QuelleResearches on the process of communication permit to understand social relations' dynamics. In this work, we focalised on vocal and visual communication signals, in two species of mangabeys. The determination of the informative value of a communication signal was approached by different ways: 1/ a sequential analysis of the signals emitted during dyadic interactions, 2/ an analysis of the structure of the signal, associated with an analysis of the emission context, 3/ an analysis of the relative positions of the individuals in the different visual fields, and 4/ a manipulation of the emission context. The differences between the species could be due to the different characteristics of their habitats in the field, which could constrain them to use preferentially one signal rather than another from another sensorial modality
Liancourt, 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.
Der volle Inhalt der QuelleThe 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.
Der volle Inhalt der QuelleIntroduced 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
VIGOUROUX, CECILE. „Microdynamique des solutions : influence des espèces paramagnétiques sur la relaxation en RMN“. Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10068.
Der volle Inhalt der QuelleSiou, 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.
Der volle Inhalt der QuellePortier, Perrine. „Sélection d'écotypes bactériens pathogènes et non-pathogènes par la plante en relation avec la différenciation en espèces génomiques chez Agrobacterium spp“. Phd thesis, Université Claude Bernard - Lyon I, 2004. http://tel.archives-ouvertes.fr/tel-00350502.
Der volle Inhalt der QuelleDommanget, 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.
Der volle Inhalt der QuelleTraditional 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.
Der volle Inhalt der QuelleBacle, Pauline. „Organisation et dynamique d'espèces chargées au voisinage de surfaces solides par modélisation de l'échelle atomique à l'échelle micrométrique“. Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066233/document.
Der volle Inhalt der QuelleThe presence of solid surfaces can modify the organization and the dynamics of charged species in solution with potential applications from the transport of polluants to formation of the firt biopolymers. We study charged systems with increasing complexity in the vicinity of a clay surface by numerical methods. The level of description should be adapted according to the relevant properties while limiting calculation times. Modeling the transport of ions in a clay sample requires to describe its complex structure but also the interactions between the mobile particles considered as punctual and the solid walls. We propose a mesoscopic model composed of a two-media system in which the displacement of the ions obtained by Brownian dynamics is conditioned by the localization of the diffusing species whith the diffusion coefficients being extracted from atomic simulations of molecular dynamics. For non-punctual species such as polyelectrolytes, the system can be simplified by constructing a coarse-grained model that allows to gain access to time scales adapted to diffusion phenomenon thanks to Langevin dynamics simulations. Two cases are considered, with an explicit or non-explicit description of the counter-ions, and the parameters are calibrated on atomic simulations. However, for complex charged molecules such as nucleotides, an atomic description is necessary to take into account the specific interactions emerging from the local structure of the molecule. Then, metadynamics simulations give quantities related to "rare" phenomena such as the adsorption of molecules on the surface of clay
Pales, Espinosa Emmanuelle. „Rôle potentiel des nutriments, des métaux et des huîtres dans les modifications de peuplements diatomiques de la baie de Bourgneuf : interactions activités anthropiques-milieu naturel“. Nantes, 1999. http://www.theses.fr/1999NANT2032.
Der volle Inhalt der QuelleRoy, Lise. „Ecologie évolutive d'un genre d'acarien hématophage : approche phylogénétique des délimitations interspécifiques et caractérisation comparative des populations de cinq espèces du genre Dermanyssus (Acari : Mesostigmata)“. Phd thesis, AgroParisTech, 2009. http://pastel.archives-ouvertes.fr/pastel-00005531.
Der volle Inhalt der QuelleKaba, 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.
Der volle Inhalt der QuelleBecause 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.
Der volle Inhalt der QuelleAttractiveness 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
Buard, Elodie. „Dynamiques des interactions espèces - espace : mise en relation des pratiques de déplacement des populations d'herbivores et de l'évolution de l'occupation du sol dans le parc de Hwange (Zimbabwe)“. Phd thesis, Université Panthéon-Sorbonne - Paris I, 2013. http://tel.archives-ouvertes.fr/tel-00806834.
Der volle Inhalt der QuelleBuard, Élodie. „Dynamiques des interactions espèces - espace : mise en relation des pratiques de déplacement des populations d'herbivores et de l'évolution de l'occupation du sol dans le parc de Hwange (Zimbabwe)“. Thesis, Paris 1, 2013. http://www.theses.fr/2013PA010606/document.
Der volle Inhalt der QuelleNational parks aim at protecting natural resources, including fauna and flora. However, some of these resources are depleting, particularly due to animal populations that converge regularly in certain places. In that context, the objective of this thesis is to propose an approach to identify interactions between movement practices of herbivore populations and land cover. We apply this approach to elephants, zebras and buffaloes of the Hwange National Park (Zimbabwe). The proposed approach combines notions from ecology, geography and geomatics. First, we identify places where spatial practices of populations are recurrent. These places are called places of convergence composed of high-density paths and stops. Diverse data sources are analyzed: animal counts and GPS tracks. The last is used to construct trajectories of animals based on concepts from Time Geography. This construction enables us to estimate the potential pressure applied by animals on land cover. Second, places where land cover has changed are extracted from remote sensing data. Last, we study the links between places of converge of populations and places of land cover changes. The results point out that data sources are complementary. They underline different types of links between animal populations and land cover, according to the species considered, the time periods and the studied areas
Hamani, 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.
Der volle Inhalt der QuelleThe 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
Martin-Blangy, Soline. „Interactions des espèces d’arbres en peuplements mélangés : effets sur la réponse à la sécheresse des arbres et rôle des mécanismes de partage des ressources en eau et en lumière“. Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0214.
Der volle Inhalt der QuelleBiodiversity, through tree species interactions, can support many ecosystem functions and services in forest ecosystems. However, in the current context of climate change, the influence of these interactions on the response of forest ecosystems to extreme climatic events, such as drought, is still under debate. Moreover, evidence for the underlying above-ground and below-ground interaction mechanisms that can explain these relationships between diversity and forest ecosystem functioning is still rare.The first objective of my thesis work was to determine the effect of tree species interactions in mixed stands on tree water relations and drought response. My second objective was to identify below-ground or above-ground mechanisms related to resource partitioning that could explain mixture effects on functioning, such as depth of water uptake by roots or canopy space filling by tree crowns.This work was carried out, within the framework of the ANR DiPTICC project, in two distinct experimental systems: an observational network in mature natural forests in the south-east of France (GMAP) and a young experimental plantation near Bordeaux (ORPHEE). I worked on three types of two-species mixtures: beech (Fagus sylvatica) - fir (Abies alba) and beech - downy oak (Quercus pubescens) along the GMAP network and birch (Betula pendula) - maritime pine (Pinus pinaster) at ORPHEE. My work is based on an empirical approach, with ecophysiological and light interception measurements, under contrasting conditions of soil water availability. Functions such as transpiration or water use efficiency (estimated by measuring carbon isotopic composition) were studied.My work shows that in young and old stands, the water relations and drought response of the species studied are little impacted by species interactions. Differences among species in water extraction depths, when present, did not necessarily result in higher water availability for species in mixed stands under drought conditions. Contrary to hypotheses often made in the literature, this suggests that belowground mechanisms would seldom drive the effects of species interactions. In contrast, I observed that the mechanisms of crown complementarity generated changes in stand structure and light interception and appeared to have a strong impact on the functioning of mixed stands.My work confirms that, for the same combination of tree species, the species-mixing effects on tree functioning are highly dependent on local environmental conditions. It is therefore essential for forest managers to take these local conditions into account when making choices about the species composition of future forests. Overall, we found no negative mixture effects on water relations, suggesting that managing forests in favor of mixed stands remains an interesting option for managers to maintain many other forest ecosystem functions and services under climate change
Filippi, Jean-José. „Étude parasitologique de Anguilla anguilla dans deux lagunes de Corse et étude ultrastructurale du tégument de trois digènes parasites de cette anguille“. Phd thesis, Université Pascal Paoli, 2013. http://tel.archives-ouvertes.fr/tel-00819285.
Der volle Inhalt der QuelleDufossé, Fabien. „Effets de la limitation en sels nutritifs, de la température et de leurs interactions sur la réponse de cinq espèces phytoplanctoniques : approche multifactorielle expérimentale en monoculture et en communauté“. Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10174/document.
Der volle Inhalt der QuelleThe effects of nitrogen and phosphorus depletion, temperature and their interaction were studied on five microalgae which differ in terms of phenology and size. By a multifactorial experimental approach, we demonstrated that nutrient effects override temperature effects, and that species from a same classical functional group could show different responses. Our results suggest that size matters for the responses of microalgae in our different conditions. Indeed, an interactive effect of temperature and nutrients was observed leading to decrease of photosynthetic activity of the small sized algae. These species also showed a high variability in their responses compared to larger ones. Furthermore, particular and dissolved carbohydrates per cell was positively influenced by nutrient limitation, temperature or their interaction, independently of cell size but rather in a specific way. Lastly, in order to highlight the relationship between productivity and diversity three experimental communities were done under nitrogen or phosphorus depletion. Our results demonstrated a better efficiency of nutrient and light absorption of communities compared to monocultures. However these communities were overall less productive than monocultures in terms of carbohydrate and biomass formation. No clear trend between diversity and productivity was shown in our study. Our results provide useful information about the responses of phytoplankton to environmental gradients and consequently of several ecosystem processes taking into accounts the modifications expected through global change
Latour, Yasmin. „Interactions sexuelles et compétitives : les moteurs comportementaux de la spéciation adaptative“. Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20047.
Der volle Inhalt der QuelleBehavioural interactions between heterospecifics, when two previously isolated populations come into contact, generate new selective pressure on traits involved in those interactions. Particularly, the traits involved in reproductive and competitive interactions evolve due to this selection, and these adaptations can affect the speciation process. Communication plays an important role in the regulation of behavioral interactions, both between and within species. Evolution of species recognition allows behavioral adjustment to the species of the encountered individuals. The empirical studies presented here aimed to test, on a model organism (two house mice subspecies), the role of sexual selection against hybrids, and of male-male interference competition, in the evolution of reproductive isolation. Our results show that sexual selection can act in th hybrid zone between Mus musculus musculus and M. m. domesticus, by reducing hybrid fitness, and by impeding gene flow through the zone. Interference competition however do not seem to be an important driver of the divergence of species-specific signals in the contact zone, and reinforcing selection is probably at the origin of this character displacement. Our results also enlighten asymmetries in homogamous preferences intensity, which could be due to differences in selective pressures depending on sex an subspecies. This dissertation ends on a discussion on interactions between process at play at secondary contact, and on the notion of species recognition
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.
Der volle Inhalt der QuelleInacio, Mamede Joao Filipe. „Interactions de la capside de lentivirus de primates avec les facteurs cellulaires de l’hôte“. Thesis, Montpellier 1, 2012. http://www.theses.fr/2012MON13524/document.
Der volle Inhalt der QuelleEver since HIV has been discovered to be the pathogenic agent that causes AIDS in 1983, much progress has been made in the field. Two different viruses are now known to infect humans, HIV-1 and HIV-2. These two distinct viruses have many sub-types and clades representing a high diversity inter and intra-individuals (quasi-species). The finding of HIV simian counterparts, the Simian Immunodeficiency Viruses (SIVs), has broadened the knowledge of primate lentiviruses and to date forty-five species of non-human primates are known to be infected with SIVs in sub-saharan Africa. It is now clear that HIV-1 and HIV-2 epidemics are the result of zoonosis from chimpanzees/gorillas and sooty mangabeys, respectively. With such a big diversity of SIVs in the wild and a frequent contact of SIV infected monkey species with humans, it is interesting that so far, only two lineages breached the species barrier and infected human populations. To be able to correctly infect a cell, a lentivirus has to overcome the installed cellular barriers known as restriction factors while at the same time correctly exploiting the established host cellular machinery. Proteins such as TRIM5, APOBEC3, Tetherin/Bst2, SAMHD1 are able to restrict retroviral infections in certain conditions. In this thesis, it has been evaluated the role of TRIM5 proteins and other capsid interacting proteins with a scope to the eventuality of a cross-species transmission infection. The results showed that human TRIM5alpha does not restrict any of the primate lentiviruses tested, and so far, no primate lentivirus is known to be restricted by it. Cyclophilin A binding and dependence is variable depending on the SIV capsid; this interaction is widespread among the primate lentiviruses phylogenetic tree but not a universal phenotype. Different capsids from SIVs have been tested for the sensitivity to the depletion of nucleoporins that are known to be used by HIV-1 in its infection; it has been concluded that the same diversity applies to the interaction with RanBP2 and Nup153. Additionally, we identified a SIV capsid that is highly restricted in human cells; this phenotype was called Ref2. With the report of a possible correlation between HIV-2 capsid variations and different levels of progression to AIDS, we devised a study aiming to identify if TRIM5 proteins were involved in this phenotype. We concluded that human TRIM5alpha does not restrict any HIV-2 capsid obtained from a HIV-2 cohort, in which individuals were presenting different levels of progression to AIDS. However, we observed a different viral fitness that correlated with pathogenicity. Moreover, Cyclophilin A dependence seems ubiquitous among all of the tested HIV-2 capsids. All of these capsids are sensitive to RanBP2 depletion and the interaction is much likely mediated by RanBP2's C-terminal motif that shares a high homology with Cyclophilin A. Summing up, it is much likely that some SIVs that still circulate in the wild can hijack the same specific cellular co-factors as HIV-1 to produce a new epidemic in humans. TRIM5α does not seem to be a potent barrier to an eventual cross-species transmission from lower primates to humans, and Cyclophilin A interaction seems to play a major role to the infection of some SIVs
Irz, Pascal. „Approche comparative des communautés piscicoles lacustres“. Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2006. http://tel.archives-ouvertes.fr/tel-00088836.
Der volle Inhalt der Quelleentre les plans d'eau en vue de contribuer à la compréhension des mécanismes qui en sont
responsables, qu'ils soient naturels ou conséquences des activités de l'Homme. Cette
approche macroécologique des peuplements en France et dans le nord-est des Etats-Unis a
montré des patrons d'addition et de remplacement d'espèces en fonction des caractéristiques
abiotiques locales et de la position géographique des plans d'eau. Le rôle structurant des
interactions biotiques est moins évident. Les introductions d'espèces modifient radicalement
la relation entre richesses locales et régionales alors que l'occupation agricole et urbaine des
bassins versants entraîne des modifications de la structure en guildes des communautés. La
convergence observée dans la réponse des communautés aux conditions climatiques et à la
taille du plan d'eau montre que la disponibilité des habitats de reproduction exerce une
contrainte forte sur les communautés locales et autorise quelques inférences sur les
conséquences du changement climatique global. L'étude des règles d'assemblage et une
réflexion relative au fonctionnement de métacommunautés à l'échelle des bassins versants
offrent des perspectives sur les plans scientifique et appliqués.
Dujardin, Gaylord. „Dynamique des communautés herbacées d'un coteau calcaire de Haute-Normandie : étude des mécanismes impliqués dans les processus de maintien et de remplacement des espèces végétales“. Rouen, 2011. http://www.theses.fr/2011ROUES013.
Der volle Inhalt der QuelleDuring the late 50s, the gradual abandonment of agro-pastoral practices in chalk hillsides initiated secondary succession dynamics which resulted in significant changes from the initial vegetation and led to structuring of a vegetation mosaic including herbaceous (short grasslands, tall grasslands and encroached grasslands) and woody communities (shrubs and forests). The present study aims at improving the knowledge of mechanisms responsible for the structuring and dynamics of herbaceous communities of a chalk hillside. To identify these mechanisms, taxonomic, comparative and functional approaches were used in field surveys and controlled conditions experiments. The first part of the thesis is devoted to the description of the herbaceous communities and analysis of successional dynamics. The main results reveal significant differences in structure, composition, diversity and species abundance between communities. The increase of social grasses and shrub encroachment are the two ecological mechanisms causing these changes. The second part of the thesis is devoted to the study of plant performance and their ability to respond to ecological changes in their local environment. The measurements of biological traits of dominant species identified phenotypic plasticity as an essential feature for their persistence during succession. Finally, the last part of this work proposes the characterization of nitrogen dynamics and water availability in different soils. These results highlighted the key role of water factor as an abiotic filter influencing the structuring of communities. Overall, the results obtained in this study clarify the mechanisms involved in the process of species persistence and replacement within the different communities, and provide new ground for the management and conservation of calcareous grasslands
El, haïkali Bouazza. „Estimations des productions organique et inorganique de quelques espèces macrophytobenthiques méditerranéennes calcifiées : interactions avec les conditions naturelles du milieu et rôle dans la variabilité circadienne de certaines caractéristiques physico-chimiques des eaux cotières“. Aix-Marseille 2, 2009. http://www.theses.fr/2004AIX22105.
Der volle Inhalt der QuelleLiarsou, 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.
Der volle Inhalt der QuelleStubenrauch, Claudia. „Étude de la production des bosons W et Z dans l'expérience UA1“. Paris 11, 1987. http://www.theses.fr/1987PA112174.
Der volle Inhalt der QuelleSince the discovery in 1983 of the intermediate vector bosons W and Z, the number of events has considerably increased so that the first time one can study their properties more precisely. A selection procedure for W → ev and Z → e+e- events, taking into account several quality criteria in a common x2, gives final samples of 294 W → ev events and 31 Z -→e+e-·events. With these two samples, it is then possible to study the production and decay properties of the intermediate vector bosons in terms of cross sections, masses and Standard Model parameters as well as angular W/Z decay distribution of charged leptons. Measuring the R =σ w / σ z ratio yields an upper limit to the number of light neutrino species. The W longitudinal and transverse momentum distributions have been analyzed in detail and confirm QCD predictions. Moreover, the vector character of the gluon, necessary in QCD, can be shown directly in large momentum W events. In conclusion, the experimental distribution: of the W-→ ev and Z-→ e+e- events confirm the Standard Model predictions (electrowea. K and QCD ) at Q2 = MW2
Baudrot, Virgile. „Modélisation des interactions trophiques impliquant des transferts de contaminants biologiques et chimiques : application à Echinococcus multilocularis et aux éléments traces métalliques“. Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2019/document.
Der volle Inhalt der QuelleStructure and strength of trophic interactions shaping food webs regulate a large part of biomass andenergy transfer in ecosystems, but also the transfer of biological and chemical contaminants. The aim ofthe PhD thesis is to develop models describing the mechanisms of contaminant transmission and using them to study the dynamics of infectious diseases and chemical pollutions, and also the response of trophic networks subject to those contaminations.[...] Following those works, a fourth step of the thesis has been to integrate trophic interactions, parasite dynamics and pollutions effects in order to study the stability of meta community (i.e. spatially connectedcommunities) and the risk of disease outbreaks. To do so, we use the theory of random matrices andwe introduced new criteria of metacommunity stability and of disease outbreak in metacommunity, both under external pressures. The study showed that external perturbations increase the risk of epidemics,but that those risks could be reduced with the dispersal of individuals (susceptible and infectious) underspecific conditions such as, for TTP, a greater number of species than that of connected ecosystems, and a smaller virulence than the contagion rate.In this way, in a context of planetary increase of anthropogenic pressures on ecosystems, this PhD thesis in modeling provides a set of tools and conceptual developments suitable to analyze quantitatively and qualitatively the transfers and impacts of contaminants in ecosystems
Blanchard, 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.
Der volle Inhalt der QuelleHuon, Mathilde. „Inter and intra specific interactions in marine habitat selection of two sympatric seal species in Northeast Atlantic“. Thesis, La Rochelle, 2017. http://www.theses.fr/2017LAROS028/document.
Der volle Inhalt der QuelleThe behavioural plasticity and the interactions between organisms are known to influence foraging habitat selection and spatial usage. In the Northeast Atlantic, greyand harbour seals live in sympatry. These two species are spread into different colonies where interactions between organisms (linked to the colony size et and the presence of one or both species) and habitat availability (linked to the prey distribution) vary locally. The objective of this PhD was to study the spatial usage and foraging habitat selection of these two species at the local scale, in contrasted situations of population dynamics. Several individuals were tagged with GPS/GSM tags in different colonies located in Ireland, Scotland and France. Telemetry data was used to characterize the seals’ trips at sea and to identify their foraging areas in order to model foraging habitat selection. While harbour seals only performed trips restricted around their haulout sites, grey seals moved between colonies. Studying habitat selection at the individual scale, for individuals moving between colonies, highlighted the influence of behavioural plasticity and suggested the influence of individual personality. At the colony scale, for both species, results highlighted the influence of habitat availability (indirectly linked to prey availability) and intra-specific interactions (linked to density dependence effects) on spatial usage and foraging habitat selection. However, the foraging habitat selection was mainly explained by the distance from the last haulout and the bathymetry. These two parameters are linked to the central place forager and benthic feeder characteristics of the seals. Furthermore, this study also highlighted, for study sites where both species occur, a spatial segregation and differences in foraging habitat selection between grey and harbourseals
Taschen, Elisa. „Interactions biotiques et biologie reproductive de la Truffe noire, Tuber melanosporum (Vittad.) : des truffières spontanées aux plantations“. Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS111/document.
Der volle Inhalt der QuelleThe Black Truffle (Tuber melanosporum Vittad.) is an ectomycorrhizal fungus spontaneously growing in open woodlands before canopy closure. Such open landscapes drastically regressed during the last century in the Mediterranean regions, and nowadays 80% of the production comes from man-made plantations where the Truffle is inoculated. Despite a large corpus of local knowledge and empirical practices, the production remains largely sporadic and unpredictable, and our knowledge of the biology and ecology of the Truffle is still fragmentary. In this work, we first analyzed the distribution of the ectomycorrhizal fungal diversity among host plants co-existing in the shrub-dominated landscapes where Truffle naturally occurs. We then analyzed the interactions between the Truffle and endo- or non-mycorrhizal plants, as they typically occur in the so-called brûlés, zones with scarce vegetation. A third part aimed at better understanding the genetic diversity of Truffle populations, with special focus on fertilization and dispersal process of this fungus with haploid lifecycle and hypogeous fruiting. In a multi-scale approach combining community ecology, experimentation and population genetics, we found that in the Mediterranean region:1) The Truffle is transiently present in rich ectomycorrhizal communities, showing a significant host preference for Q. ilex, in assemblies made of numerous multi-host fungal species. 2) Some endo- or non-mycorrhizal plants species, that were supposed to provide beneficial effect on the Truffle, can be experimentally shown to stimulate the development of T. melanosporum mycelium in soil, and indirectly trigger plant-plant interactions (between oak and endomycorrhizal plants). The early brûlé symptoms could at least partially result from a Truffle's inhibitor effect on seed germination.3) At truffle ground scale, gene flow is limited, and mating occurs between genetically and physically close parents. Despite probable hermaphroditism of the Truffle, paternal parents are poorly detectable, certainly of smaller size than maternal ones (these forming nourishing tissue of the ascocarp). Cultural practices could favor genetic mixing/diversity at brûlé scale, but at the regional scale, no difference in genetic diversity was found between spontaneous and planted compartments.This work revealed the richness of biotic interactions involving the black Truffle and the plant as well as the fungal diversity in both artificial and spontaneous truffle-ground of the Mediterranean region. These results enlighten the reproductive biology of the species, and pave the way for practices integrating the biological diversity of truffle-grounds and the development of further in situ experimentations. Key words: Arbutus unedo, Cistus albidus, community ecology, domestication, empirical practices, local knowledge, experimental approach, inbreeding, isolation by distance, ITS, Mediterranean forests, mesocosms, microsatellites, mycorrhiza, population genetics, qPCR, Quercus ilex, Q. coccifera, secondary successions