Diversity of MHC class II DRB alleles in the Northern chamois genus Rupicapra

Major histocompatibility complex (MHC) genes are commonly used markers for monitoring adaptive genetic and evolutionary potential of species. In this study, we investigated genetic variation of the MHC class II DRB locus in the chamois genus Rupicapra by using next-generation sequencing. Sequencing of 102 samples led to the identification of 25 alleles, 11 of which are novel. The high ratio of the relative rates of nonsynonymous to synonymous mutations (dN/dS) suggests a signal of positive selection on this locus. We analyzed patterns of genetic variation within and among 2 subspecies of Northern Chamois and compared them to previously published studies using neutral markers to provide a basis for assessing the effects of demographic processes. Our analyses have shown that alleles are likely to be maintained by balancing selection in different populations with similar frequencies and that this mechanism also works in small, isolated populations that are strongly affected by genetic drift.