Data from: Reduced-representation sequencing detects trans-Arctic connectivity and local adaptation in polar cod (Boreogadus saida)

Information on connectivity and genetic structure of marine organisms
remains sparse in frontier ecosystems such as the Arctic Ocean. Filling
these knowledge gaps becomes increasingly urgent, as the Arctic is
undergoing rapid physical, ecological, and socio-economic changes. The
abundant and widely distributed polar cod (Boreogadus saida) is highly
adapted to Arctic waters, and its larvae and juveniles live in close
association with sea ice. Through a reduced-representation sequencing
approach, this study explored the spatial genetic structure of polar cod
at a circum-Arctic scale. Genomic variation was partitioned into neutral
and adaptive components to respectively investigate genetic connectivity
and local adaptation. Based on 922 high-quality single nucleotide
polymorphism (SNP) markers genotyped in 611 polar cod, broad-scale
differentiation was detected among three groups: (i) Beaufort-Chukchi
seas, (ii) all regions connected by the Transpolar Drift, ranging from the
Laptev Sea to Iceland, including the European Arctic, and (iii) West
Greenland. Patterns of neutral genetic structure suggested broadscale
oceanographic and sea ice drift features (i.e. Beaufort Gyre and
Transpolar Drift) as important drivers of connectivity. Genomic variation
at 35 outlier loci indicated adaptive divergence of the West Greenland,
and the Beaufort-Chukchi Seas populations, possibly driven by
environmental conditions. Sea ice decline and changing ocean currents can
alter or disrupt connectivity between polar cod from the three genetic
groups, potentially undermining their resilience to climate change, even
in putative refugia, such as the Central Arctic Ocean and the Arctic
Archipelago.