We are currently confronted to a crisis of extinction affecting biodiversity as a result of global change (habitat fragmentation, climate warming, etc.) that are pushing the limits of the tolerance to environmental constraints of plant and animal species. Available and suitable habitats where species could find refuge are rare. Species survival will hence depend largely on their ability to adapt. Will that adaptive potential be sufficient for species to maintain themselves? Today, we have methods and data from the domain of population genetics that allow us to evaluate genetic diversity of the basis of neutral molecular markers, which are hence independent from natural selection. Those tools allow us to identify the populations that are the least diverse and the most isolated, for which genetic diversity is suffering erosion, over the range of species geographic distribution. Methods in ecology allow us to characterise the environmental conditions defining the habitat of species across the geographic distribution. On the basis of climate change, it is possible to project to some extent what will the environment be like in the future in the current habitat of species. Quantitative genetics methods allow us to evaluate the degree of local adaptation of populations and to quantify their potential to respond to selection. Species have adapted to their environment in the past, and such adaptation was sometimes fast. Is this option still available to them today? It is surprising that those three scientific domains are so rarely bridged to evaluate the ability of species to adapt to global change, especially when considering the potential positive input that such multidisciplinary approaches would have on conservation strategies and genetic resources management. In this project, we will conduct an empirical approach at the intersection of those three scientific domains in order to evaluate the ability to adapt of the plant species Antirrhinum majus to environmental changes. We have characterised some part of the evolutionary history of A. majus. We identified patterns of geographic expansion and found evidence that some populations over the 55 populations that we surveyed across the entire geographic range of the species (Pyrenees and Mediterranean coast) had exchanged genes in the past. We expect that populations originating from areas where gene exchanges were documented will be less locally adapted than others because gene flow will have homogenised their gene pool and therefore limited their adaptive divergence. We also expect those populations to have a greater potential to adapt because gene exchanges will have broaden their heritable variation. We will test those hypotheses in turn by conducting a local adaptation experiment and a response to selection experiment on multiple populations. Studying adaptive processes without an environmental perspective on the relationship between environmental selective pressures and fitness makes no sense. We have characterised the ecological niche of A. majus, i.e., the range of environmental conditions suitable for its populations across its entire geographic range. Unsurprisingly, populations from the highest and lowest altitudes were found to be confronted to more extreme conditions than populations from intermediate altitudes, respectively more rigorous winters and stronger drought episodes. We will simulate climate change by transplanting populations in natura towards lower altitudes and we will characterise the relationship between plant fitness and the genetic architecture of quantitative traits. Population genetics and ecological niche data are accumulating in the scientific literature. We will provide the community of scientists and conservation managers with a tool box of methods that we used in our approach and with practical guidelines to quantify directly the adaptive potential of species.

Global changes expose wild populations to increasing pollution and emerging pathogens, which could have complex interactive effects on organism health. However, the ways in which multiple stressors and intraspecific variability scale up to shape health and disease risk remain poorly understood. Based on an “Ecohealth” perspective at the crossroad between ecotoxicology, health ecology and evolutionary ecology, this project will explore the impacts of contamination on host-pathogen interactions across generations, from molecules to populations, using heterogeneous populations of brown trout exposed to an emerging pathogen in metal contaminated areas due to historic and contemporary mining activities. This project will offer a novel conceptual framework to elucidate the environmental, physiological and genetic determinisms of variations in resistance/tolerance to stressors, and improve our ability to predict the effects of pollution on wildlife health and emerging diseases.

Habitat loss and fragmentation are major threats affecting more than 85% of terrestrial threatened species and thus menacing biodiversity. For instance, 40% of original forest cover has been lost through human activity. The problem of habitat loss is made worse by the fragmentation of natural habitats, which results in smaller, more isolated sub-populations with reduced possibilities for dispersal. Fragmented populations follow a metapopulation dynamic dependent on local extinction, dispersal into locally extinct patches (colonization) and into extant patches (reinforcement). Reduced dispersal can hinder the recolonization of patches where sub-populations have become extinct, leading to stochastic local and ultimately global extinctions. Therefore, habitat fragmentation affects species occurrence through patch isolation. In FRADISYN, we study dispersal processes, the adaptive mechanisms allowing connectivity between patches and thus species to overcome this spatial isolation. We aim to integrate inter-individual variability in dispersal decisions, a recent advance in dispersal theory, into the dynamic of fragmented populations. Such inter-individual variability arises from the variability in phenotypic traits that shapes individual success in diverse ecological conditions and, in turn, should produce inter-individual differences in habitat selection. Those various associations between phenotypic traits and habitat preferences, named dispersal syndromes, should affect metapopulations dynamics. We predict that colonization and reinforcement involve individuals of different syndromes. Here, we aim to experimentally study, for the first time, the heterogeneity in dispersal syndromes, by exploring the relations between phenotypic traits and habitat preferences, the relationship between habitat preferences and fitness outcomes and the mechanisms producing and maintaining the heterogeneity in dispersal syndromes. Our project will use an integrative approach blending molecular, behavioral and modeling analyses. We will first quantify the relations between habitat preferences and behavioral types that are phenotypic traits likely to drive dispersal decisions. We will then study 1) the role of sequence polymorphism and expression of genes involved in neurochemicals in the production of those relations and 2) the heritability, consistency and effects on performance of established dispersal syndromes explaining their maintenance. Finally, we will integrate results from those tasks into metapopulation dynamic with experimental and modeling approaches. The success of FRADISYN requires a variety of knowledge brought by a team of young researchers from two labs (EDB and SEEM) and a unique and innovating experimental system of metapopulations available at SEEM. This project will merge the knowledge and skills from these two labs to develop the link between population, behavioral and evolutionary ecology. Given the importance of dispersal for species adaptability to changing environments, we need a more integrative comprehension of dispersal processes to understand how, after fragmentation, species can overcome isolation between patches to increase connectivity within the landscape. FRADISYN proposes a highly innovative approach that integrates explicitly within-species phenotypic variation into fragmented population dynamic models. We believe our results will be of wide interest for scientific communities and thus will be published in high ranking journals.

Global patterns of biodiversity are driven by a number of processes that can be analyzed by studying the turnover in species composition across sampled location (i.e. beta diversity). In theory, there are eight possible combinations of high versus low taxonomic ß-diversity, phylogenetic ß-diversity and functional ß-diversity, and a general predictive framework has only recently emerged to propose hypotheses linking the observed decoupling patterns to underlying mechanisms. In the DEBIT project, we aim at evaluating this predictive framework by testing spatially explicit hypotheses for the effect of geographical isolation and environmental dissimilarity on patterns of biodiversity. We will focus on analyzing biodiversity dimensions of aquatic ecosystems (river systems) in the tropical environment of French Guiana using two taxonomic groups: fishes and insects. We will use innovative community-level modeling to evaluate how human induced modifications affect different facets of biodiversity.

Tropical regions harbour more species than temperate zones. This pattern, described since more than two centuries as the latitudinal gradient of diversity, remains one of the great mysteries of ecology. In this project, I choose to address three major unanswered fundamental questions regarding the construction of the latitudinal gradient of diversity: (1) Is extinction higher in temperate regions than in the tropics? It is notoriously difficult to estimate extinction rate and its role in the construction of diversity patterns remains poorly understood. Using recent birth-death diversification models, I will analyze the largest paleontological databases available to estimate the contribution of extinction to latitudinal differences in diversity. The second question is (2) Are species interactions stronger in the tropics? Interspecific interactions have often been proposed as one of the main factors favoring speciation in the tropics. Using phenotypic evolution models and global species functional trait data, I will test whether species interactions are detected more often in the tropics than in temperate zones. And finally, I will study the question: (3) What are the molecular mechanisms of adaptation to high latitudes? Using a very large genomic dataset collected in the field on a latitude gradient from California to Alaska, I will compare adaptations in two distant species: the three-spined stickleback and the chinook salmon. This comparison will aim to better understand whether adaptations to latitude are evolving de novo or using a common architecture between species. This project proposes to study the current key questions concerning the understanding of the latitudinal gradient of diversity, while using a multidisciplinary approach integrating paleontology, comparative methods, populations genomics and the most recent global data.