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

Demographic declines have important genomic consequences for population viability, since they can lead to losses in genome diversity, increased inbreeding, and accumulation of genetic load. Scandinavia was colonised 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 population became even more fragmented in the early 1900's due to human persecution, and experienced an additional decline in the 1980's. 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 already 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.