Contrasting patterns of MHC and microsatellite diversity in social and solitary tuco-tucos (Rodentia: Ctenomyidae)

Abstract

MHC diversity in two species of tuco-tuco (Rodentia: Ctenomyidae) is compared and evaluated in light of behavioral and demographic differences between the study species. MHC diversity is also compared to diversity at nine microsatellite loci to explore interspecific patterns of genetic variation at functional and non-functional nuclear markers. While it is impossible to tease apart the relative effects of selection, history, current demography, and social structure, it is clear that these factors have differentially affected MHC and microsatellite loci in tuco-tucos. Microsatellite polymorphism in Ctenomys sociabilis is consistently less than that in Ctenomys haigi although microsatellite diversity in both species is consistent with Hardy-Weinberg expectations. In contrast, MHC polymorphism is greater in C. sociabilis. Heterozygosity levels in both species appear to be reduced relative to Hardy-Weinberg expectations although this deviation is significant only for C. haigi. These data suggest that the factors shaping genetic diversity in tuco-tucos differ markedly between microsatellite and MHC loci.