Spatial distribution of microsatellite and MHC-DRB exon 2 gene variability in the Jamaican fruit bat (Artibeus jamaicensis) in Mexico

Genetic diversity is essential to the evolutionary and adaptive potential of a species. Several empirical genetic studies have highlighted the importance of considering both neutral and adaptive genetic variation when characterizing microevolutionary dynamics. Genes at the major histocompatibility complex (MHC) have become excellent models for researching adaptive variation and natural selection, because of the crucial role they play against pathogens. The Jamaican fruit bat, Artibeus jamaicensis, is one of the most common and well-studied Neotropical mammals and is characterized by generalist feeding habits, high dispersal capability, and abundant populations. Fifteen localities of Artibeus jamaicensis were genetically assessed using ten neutral microsatellites and one expressed MHC class II locus (DRB) in order to detect footprints of balancing selection. Extensive polymorphism was found at both markers. Overall, 161 alleles were identified at DRB exon 2 gene, and 315 at microsatellites. The observed and expected heterozygosity averaged over all localities (±SD) was 0.756 ± 0.15 and 0.885 ± 0.11, respectively, with all localities in Hardy–Weinberg equilibrium. Pairwise genetic differentiation estimates were generally significant, but the overall differentiation was lower at DRB gene (F_st = 0.039) than at microsatellites (F_st = 0.154). We detected significant isolation by distance at microsatellite loci, but not at DRB exon 2 gene. STRUCTURE and BAPS analyses detected a population genetic structure made up of five defined clusters. Our results suggest that balancing selection has maintained the allele frequencies of DRB exon 2 gene across the distribution of A. jamaicensis in Mexico.