No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Landscape genetic approaches allow to study effects of landscape to population microevolution. Landscape can influence gene flow even in large carnivores with good dispersal ability. Understanding the influence of landscape to the gene flow between populations is crucial for species conservation, especially in the species with low population densities. Aim of the study was to describe genetic structure of the grey wolf (Canis lupus) and snow leopard (Panthera uncia) in selected areas and to determine the influence of the landscape features on observed structure. Non-invasive genetic samples of snow leopard from Nepal were analysed, as well as invasive and non-invasive samples of grey wolf from Central Europe. Population structure was determined a posteriori using Bayesian clustering approaches that integrate genetic and geographical data, and compared to landscape connectivity models. Population structure of snow leopards is mostly influenced by human presence and presence of frequented roads, which represent a substantial dispersal barrier. Habitat suitable for this species is greatly restricted by altitude, however, during dispersal they are able to overcome areas with higher elevation than what is optimal for them. Pronounced genetic difference was found between central European and Carpathian...

Ce projet vise à comprendre comment la structure génétique intra-spécifique d'espèces végétales tropicales emblématiques et de l’espèce humaine a été affectée par les variations spatio-temporelles de l’environnement actuel et passé. Nous avons développé une approche d’inférence génétique basée sur la théorie de la coalescence pour évaluer l’influence potentielle des changements climatiques passés sur l’évolution de la distribution géographique et de la diversité génétique neutre et/ou adaptative d’Amborella trichopoda Baill. en Nouvelle-Calédonie (espèce-sœur des angiospermes, données NGS et microsatellites), de Coffea canephora Pierre ex A. Froehn en Afrique tropicale (caféier Robusta, données NGS) et de populations européenne et africaine (Luhya, Kenya) d’humains anatomiquement modernes (données NGS issues du Projet 1000 Génomes). Nos travaux suggèrent que les fluctuations climatiques du Pleistocène tardif ont joué un rôle majeur sur l’évolution de la diversité génétique des espèces étudiées de milieux tropicaux et tempérés, avec une empreinte remarquable du Dernier Maximum Glaciaire (DMG, 21 000 ans avant le présent). Les contractions démographiques associées à la glaciation planétaire ont vraisemblablement conduit à la divergence entre les lignées génétiques d’Amborella et participé à l’accumulation des différences génétiques entre les lignées de C. canephora. Nos résultats suggèrent que les événements de glaciation planétaire ont probablement entraîné une différenciation génétique idiosyncratique dans les forêts tropicales humides mais l’intensité de cette réponse semble avoir varié entre espèces. Nous avons également identifié de nombreux événements passés de sélection dans les génomes de la population humaine européenne qui ont été vraisemblablement provoquées par les conditions environnementales au cours du DMG. Les adaptations phénotypiques associées ont probablement assuré le maintien de l’expansion démographique en dépit des pressions de sélection nouvelles auxquelles les populations étaient confrontées au cours du dernier âge glaciaire en Europe. / This project aims at understanding how the structure of the intra-specific genetic diversity in emblematic tropical plant species and in the human species was shaped by the spatiotemporal variation of current and past environments. We developed a genetic inference approach based on the coalescent theory to assess the potential impact of past climatic change onto the evolution of the geographic range and of the neutral and/or adaptive genetic diversity in Amborella trichopoda Baill. in New Caledonia (sister-species of all extant angiosperms, NGS and microsatellite datasets), in Coffea canephora Pierre ex A. Froehn in tropical Africa (Robusta coffee, NGS dataset) and in North-Western European and African (Luhya, Kenya) human populations (NGS dataset 1000 Genomes Project). We found that the climatic fluctuations of the Late Pleistocene influenced the evolution of genetic diversity in these species distributed in temperate and tropical environments. The environmental conditions during the Last Glacial Maximum (LGM, 21.000 years before present) appear as an important factor. The demographic contraction associated with the last global glaciation influenced the divergence between Amborella genetic lineages and contributed to the accumulation of genetic differences between C. canephora lineages. Our results suggest that global glaciation events likely drove idiosyncratic genetic differentiation in tropical rain forests but the intensity of this response varied between species. We also identified multiple events of selection in the genomes of the European human population which were likely triggered by the environmental conditions during the LGM. The associated phenotypic adaptations probably allowed the paleo-populations to maintain their demographic expansion despite the new kinds of selective pressure they faced during the last glacial age in Europe.

<p>Because species respond individually to climate change, understanding community assembly requires examination of multiple species from a diversity of forest niches. I present the post-glacial phylogeographic history of an understory, parasitic herb (<italic>Epifagus virginiana</italic>, beechdrop) that has an obligate and host specific relationship with a common eastern North American hardwood tree (<italic>Fagus grandifolia</italic>, American beech). The migration histories of the host and parasite are compared to elucidate potential limits on the parasite's range and to understand their responses to shared climate change. Two chloroplast DNA regions were sequenced and 9 microsatellite loci genotyped from parasite specimens collected throughout the host's range. These data were compared with available cpDNA sequences from the host (McLachlan et al. 2005) and host fossil pollen records from the last 21,000 years (Williams et al. 2004). Analyses of genetic diversity reveal high population differentiation in the parasite's southern range, a possible result of long term isolation within multiple southern glacial refuges. Estimates of migration rates and divergence times using Bayesian coalescent methods show the parasite initiating its post-glacial range expansion by migrating northward into the northeast from southern areas, then westward into the midwest, a pattern consistent with the development of high density beech forests. This result is strongly confirmed through spatial linear regression models, which show host density plays a significant role in structuring parasite populations, while the initial migration routes of the host are irrelevant to parasite colonization patterns. Host density is then used as a proxy for the parasite's habitat quality in an effort to identify the geographic locations of its migration corridors. Habitat cost models are parameterized through use of the parasite's genetic data, and landscape path analyses based on the habitat map show a major migration corridor south of the Great Lakes connecting the northeast and midwest. Host density was the major determinant controlling the parasite's range expansion, suggesting a lag time between host and parasite colonization of new territory. Parasites and other highly specialized species may generally migrate slower due to their complex landscape requirements, resulting in disassociation of forest assemblages during these times. From these results, the low migration capacities of highly specialized species may be insufficient to outrun extirpation from their current ranges.</p> / Dissertation

Les activités d'origines anthropiques entraînent des modifications profondes du paysage : dans ce contexte, le succès de dispersion revêt une grande importance pour la persistance à long terme des populations animales et végétales. La génétique du paysage est une discipline récente qui permet de détecter et de modéliser les flux de dispersion de manière indirecte par le biais de l'identification des flux de gènes dans l'espace. Bien qu'il ait été suggéré delongue date qu'un échantillonnage individu-centré pouvait permettre de s'affranchir de certains biais liés à unedélimitation a priorides populations, les études portant sur des organismes présentant une distribution spatiale discontinue restent malgré tout le plus souvent basées sur un échantillonnage réalisé à l'échelle populationnelle. C'est sur cette thématique qu'ont porté mes travaux de thèse. Des résultats obtenus par simulations montrent qu'augmenter le nombre de points échantillonnés dans l'espace au détriment du nombre d'individus par agrégat peut permettre une meilleure détection de l'influence de la matrice sur les flux de gènes, quelque soit le régime de dispersion et le contexte paysager considérés. Appliqué à l'étude de la dispersion du triton alpestre Ichthyosaura alpestris, d'une part en paysage fragmenté par des infrastructure linéaires de transport (isolation par barrières aux flux de gènes IBB) et d'autres part en paysage agricole (isolation par résistance de la matrice paysagère IBR), l'échantillonnage individu-centré apparaît comme une alternative flexible et efficace à l'échantillonnnage populationnel classique. / Anthropogenic activitites lead to profound landscape alterations : dispersal success thus holds a paramount importance for long-term persistence of populations. Landscape genetics is a recent discipline aiming to detect and describe dispersal patterns through indirect estimations of gene flow. Although the use of an individual-based sampling scheme has been proposed for a ;ong time to get round the issue of an a priori delimitation of population boundaries, most landscape gentic studies are still based on a population-based sampling scheme. results from simulations showed that decreasing the sampling coverage on individuals within populations in favour of a better sampling coverage of aggregates through space allowed a better detection of the impacts of landscape on gene flow, whatever the individual dispersal behaviour or the landscape configuration. when considering the dispersal patterns in the alpine newt Ichthyosaura alpestris, both in the vicinity of large transport infrastructures (Isolation-by-barrier IBB) and in agricultural landscape (Isolation-by-landscape-resistance IBR), the individual-based sampling scheme proved to be a flexible and efficient methodological alternative to the more conventional population-based sampling scheme.