Genetic polymorphisms and the independent evolution of major histocompatibility complex class II‐DRBin sibling bat speciesRhinolophus episcopusandRhinolophus siamensis

Abstract

The relative roles of different microevolutionary forces, like natural selection and demographic processes, in affecting genetic variation are of great scientific interest. In this study, we investigated recent divergence of the sibling bat species Rhinolophus episcopus and R. siamensis, which share a partially sympatric distribution and have different phenotypic characteristics among populations. We combined neutral [microsatellite (SSR)] and adaptive [major histocompatibility complex (MHC) class II-DRB locus] markers to investigate the evolution of adaptive markers and disentangle the relative effects of neutral and adaptive microevolutionary forces on this MHC gene region. Our results revealed a stronger level of genetic differentiation in SSRs than in MHC genes of both species, which indicates effects of balancing selection on the geographical variation of MHC genes. However, we detected significant correlations in genetic differentiation between MHC and SSRs in R. episcopus, indicating that demographic processes have influenced the level of MHC genetic diversity in this species. In addition, significant moderate genetic differentiation was detected in sympatric populations and no alleles were shared between the two species. Therefore, we speculate that these sibling species have been subject to independent adaptive evolutionary processes.