RT Journal Article SR Electronic T1 Population structure and genomic evidence for local adaptation to freshwater and marine environments in anadromous Arctic Char (Salvelinus alpinus) throughout Nunavik, Canada JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.04.29.066449 DO 10.1101/2020.04.29.066449 A1 Xavier Dallaire A1 Éric Normandeau A1 Julien Mainguy A1 Jean-Éric Tremblay A1 Louis Bernatchez A1 Jean-Sébastien Moore YR 2020 UL http://biorxiv.org/content/early/2020/04/29/2020.04.29.066449.abstract AB Distinguishing neutral and adaptive genetic variation is one of the main challenges in investigating processes shaping population structure in the wild. Despite marine environments being key habitats for the growth of anadromous fishes, landscape genomics studies on salmonids have generally focused on identifying signatures of adaptation to freshwater habitats. Unlike most other anadromous salmonids, Arctic Char (Salvelinus alpinus) occupy coastal habitats near their overwintering rivers during their marine phase, thus making adaptation to marine habitats possible. The aim of this study was to document the neutral and adaptive variation of populations among anadromous Arctic Char in Nunavik and bordering regions. We used GBS to genotype 20,327 filtered single nucleotide polymorphisms (SNPs) for 650 individuals sampled in 23 locations along >2,000 km of coastline. Our results reveal a hierarchical genetic structure, whereby neighboring hydrographic systems harbour distinct populations grouping within major oceanographic basins, namely the Hudson Bay, Hudson Strait, Ungava Bay and Labrador Sea. We found genetic diversity and differentiation to be influenced by both post-glacial recolonization history and by patterns of isolation-by-distance reflecting contemporary gene flow. Furthermore, using three gene-environment association (GEA) methods we found genomic evidence for local adaptation to both freshwater and marine habitats, especially in relation to sea-surface and air temperatures during summer, precipitation, and salinity. This study is among the first to explicitly explore the genetic basis of marine adaptations in salmonids and highlights the complex interactions in selective pressures over the lifespan of anadromous fishes.Competing Interest StatementThe authors have declared no competing interest.