Diversity of MHC class II DRB alleles and mitochondrial DNA in northern and eastern European pine marten, Martes martes (Mammalia: Mustelidae)

Abstract

Abstract Four mitochondrial phylogroups are distinguished in the European pine marten (Martes martes), two of which, FNR1/2, are shared with the more easterly sister species, the sable (Martes zibellina). Here, we found that the phylogroup frequencies differed markedly between the southern Finland and western Russia populations in the eastern part of the range of Martes martes, suggesting differential introgression from M. zibellina in these regions. We also examined the diversity of a protein-coding gene, MHC class II DRB, in these two Martes species. We detected 16 functional Martes martes DRB alleles (Mama-DRBs), including several codons that seem to have undergone positive selection, and eight presumed pseudogenes (Mama-DRB*PSs); some alleles/pseudogenes were geographically widespread and others restricted. In a broader carnivoran DRB tree, all Mama-DRBs grouped within a mustelid clade, four in a basal group comprising alleles from early-diverged species and the others in a derived group containing alleles from more recently diverged species. Many alleles showed trans-species polymorphism, suggesting that Mama-DRBs have evolved under pathogen-driven balancing selection. Three of six Mama-DRBs and one of four pseudogenes shared with Martes zibellina were restricted to the FNR1/2 mitochondrial DNA phylogroups, pointing to the possibility that genetic introgression from Martes zibellina might have contributed to Mama-DRB diversity and thus adaptability.