Abstracts (first author)
Influence of seascape and migratory patterns on coastal brown trout genetic structure (Salmo trutta)
Understanding how anthropogenic and natural factors influence movement patterns of wild organisms is of prime importance in conservation biology. Most animal species live in spatially and temporally heterogeneous landscapes where resources are unequally spread. Consequently, individuals must adjust their migratory behaviour to avoid adverse environmental conditions and reach suitable areas for feeding and breeding. In the present work, we studied populations of brown trout (Salmo trutta) from the rivers of the French Channel coast that display a large continuum of migratory strategies from complete freshwater residence to anadromy (sea trout). To clarify the influence of life-history strategies and natural environmental factors on population connectivity, we used an integrated approach that combines GIS data on landscape structure, patterns of life history variation and inferences of dispersal based on neutral genetic markers. Landscape genetic analyses revealed a hierarchical genetic structure with two main genetic units corresponding to the eastern and western marine ecoregions of the English Channel delineated by the Cotentin peninsula. Within these two clusters, the spatial variation of migratory strategies appears to influence the patterns of isolation by distance and we observed a latitudinal increase in population genetic isolation. Moreover, least-cost path modelling suggests that sea trout preferentially disperse through soft bottom areas in brackish and shallow waters where they find their favourite prey. Overall, these results point out the need to take into account the spatial variability of life history and landscape heterogeneity at large scale when studying the ecology and evolution of long distance migratory animals.