Population structure of the endangered Siberian flying squirrel <i>Pteromys volans</i> revealed by genomic and mitochondrial data

The Siberian flying squirrel Pteromys volans is an arboreal rodent with a distribution range that covers large parts of the Eurasian taiga forest zone. However, extensive forestry has resulted in widespread local population declines and extinctions in recent decades. Even though it is widely distributed in Eurasia, almost nothing is known about its phylogeography. Here we used genome‐wide single nucleotide polymorphisms (SNPs) and mitochondrial DNA (mtDNA) to investigate population structure, connectivity and genetic diversity in different sites throughout its distribution. Overall, the species shows low nucleotide diversity and heterozygosity. Locations in Finland, on the western edge of the distribution, had the lowest diversities in genomic SNPs and mtDNA, while individuals in the Far East (Sikhote‐Alin, Russia) show the highest diversity. These findings fit with a rapid range expansion from the Far East to the west. We found a strong genetic differentiation between Sikhote‐Alin and all other populations investigated, which might warrant a revision of their taxonomic classification. The inferred low genetic diversities at the western edge of their distribution are especially worrisome as they are currently experiencing strong population declines and major habitat changes, which can be especially detrimental when standing variation is low. Thus, there is a pressing need to revise the species' conservation status.