MHC II DRB variation and trans-species polymorphism in the golden snub-nosed monkey (Rhinopithecus roxellana)

Genetic variation is generally believed to be important in studying endangered species’ adaptive potential. Early studies assessed genetic diversity using nearly neutral markers, such as microsatellite loci and mitochondrial DNA (mtDNA), which are very informative for phylogenetic and phylogeographic reconstructions. However, the variation at these loci cannot provide direct information on selective processes involving the interaction of individuals with their environment, or on the capability to resist continuously evolving pathogens and parasites. The importance of genetic diversity at informative adaptive markers, such as major histocompatibility complex (MHC) genes, is increasingly being realized, especially in endangered, isolated species. Small population size and isolation make the golden snub-nosed monkey (Rhinopithecus roxellana) particularly susceptible to genetic variation losses through inbreeding and restricted gene flow. In this study, we compared the genetic variation and population structure of microsatellites, mtDNA, and the most relevant adaptive region of the MHC II-DRB genes in the golden snub-nosed monkey. We examined three Chinese R. roxellana populations and found the same variation patterns in all gene regions, with the population from Shennongjia population, Hubei Province, showing the lowest polymorphism among three populations. Genetic drift that outweighed balancing selection and the founder effect in these populations may explain the similar genetic variation pattern found in these neutral and adaptive genes.