Sea ice reduction drives genetic differentiation among Barents Sea polar bears

Loss of Arctic sea ice due to climate change is predicted to reduce both
genetic diversity and gene flow in ice-dependent species, with potential
negative consequences for their long-term viability. Here, we tested for
the population-genetic impacts of reduced sea ice cover on the polar bear
(Ursus maritimus) sampled across two decades (1995–2016) from the Svalbard
Archipelago, Norway, an area that is affected by rapid sea ice loss in the
Arctic Barents Sea. We analysed genetic variation at 22 microsatellite
loci for 626 polar bears from four sampling areas within the archipelago.
Our results revealed a 3-10% loss of genetic diversity across the study
period, accompanied by a near 200% in genetic differentiation across
regions. These effects may best be explained by a decrease in gene flow
caused by habitat fragmentation due to loss of sea ice coverage, resulting
in increased inbreeding of local polar bears within the focal sampling
areas in the Svalbard Archipelago. This study illustrates the importance
of genetic monitoring for developing adaptive management strategies for
polar bears and other ice-dependent species.