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The wolverine (Gulo gulo) in Finland has undergone significant population declines in the past. Since major histocompatibility complex (MHC) genes encode proteins involved in pathogen recognition, the diversity of these genes provides insights into the immunological fitness of regional populations. We sequenced 862 amplicons (242 bp) of MHC class II DRB exon 2 from 32 Finnish wolverines and identified 11 functional alleles and three pseudogenes. A molecular phylogenetic analysis indicated trans-species polymorphism, and PAML and MEME analyses indicated positive selection, suggesting that the Finnish wolverine DRB genes have evolved under balancing and positive selection. In contrast to DRB gene analyses in other species, allele frequencies in the Finnish wolverines clearly indicated the existence of two regional subpopulations, congruent with previous studies based on neutral genetic markers. In the Finnish wolverine, rapid population declines in the past have promoted genetic drift, resulting in a lower genetic diversity of DRB loci, including fewer alleles and positively selected sites, than other mustelid species analyzed previously. Our data suggest that the MHC region in the Finnish wolverine population was likely affected by a recent bottleneck.

Although the present-day distributional boundary between the European badger (Meles meles) and the Asian badger (Meles leucurus) is around the Volga River, studies of ancient bone remains have indicated changes in the distribution of M. meles and M. leucurus in the Urals-Volga region during the Holocene. To examine past changes in distribution using genetic data, changes in genetic diversity, and the relationships of Holocene to modern populations, we sequenced ~150 bp of the mitochondrial DNA control region from the 44 ancient badger remains excavated from European Russian, Ural and Western Siberian sites, and we detected 12 haplotypes. Our study revealed Holocene changes in the distributional boundary between these badger species. Meles meles inhabited the Ural Mountains east of the Volga River in the Early Holocene, whereas M. leucurus expanded its distribution westwards, starting ~2500 years ago. Thereafter, M. leucurus rapidly replaced M. meles in the region between the Urals and the Volga, resulting in the present-day boundary in the Volga-Kama region. Among the 12 haplotypes detected, three for M. leucurus and four for M. meles were identical to partial sequences of haplotypes detected in modern populations, indicating considerable genetic continuity between Holocene and modern populations. © 2020 The Linnean Society of London, Biological Journal of the Linnean Society.