Genomic basis of deep‐water adaptation in Arctic Charr (Salvelinus alpinus) morphs

Colonization of extreme habitats requires extensive adaptation to novel environmental challenges. Deep-water environments (>50 m) have high hydrostatic pressure, low temperature, and low light, requiring physiological and visual system adaptation, but genomic mechanisms underlying evolution in these environments are rarely known. Post-glacial colonization of Gander Lake in Newfoundland, Canada, by Arctic Charr (Salvelinus alpinus) provides the opportunity to study the genomic basis of adaptation to extreme deep-water environments. Here, we compare genomic and morphometric divergence between a phenotypically divergent deep-water, demersal morph adapted to depths of up to 288m and a larger, piscivorous morph occupying shallower depths. Using a SNP array and resequencing of nuclear and mitochondrial genomes, we find moderate genetic divergence (FST = 0.15 - 0.11) between morphs, consistent with divergence in body shape and size, despite absence of mitochondrial genome divergence. Outlie...