Temporal genomic change in the Scandinavian Arctic fox (Vulpes lagopus)

Demographic declines have important consequences for population viability, since they can lead to losses in genome diversity, as well as increased inbreeding and expression of deleterious mutations. Scandinavia was colonized by the Arctic fox (Vulpes lagopus) at the Pleistocene/Holocene transition, and the population has since been on the periphery of the global distribution. The Scandinavian population became even more fragmented in the early 1900s due to human persecution, and experienced an additional decline in the 1980s. We generated high-coverage genomes from pre-bottleneck, as well as modern Scandinavian and Russian specimens, and found that genome-wide diversity was lower and inbreeding higher in Scandinavia compared to the Siberian population, even prior to the historical bottleneck, most likely reflecting the long-term partial isolation and recent postglacial origin of the Scandinavian population. The southern subpopulation has the highest inbreeding levels, likely due to having been recently founded and highly isolated. Our results also show that although inbreeding increased substantially over the past century, the amount of total genetic load did not change. Overall, these findings illustrate the utility of a temporal approach to disentangle the genomic consequences of recent declines from ancient biogeographic processes.