To explore the effects of behavior and demography on balancing selection at major histocompatibility complex (MHC) loci, we examined allelic diversity at exon 2 of the MHC class II DQβ locus in a social and a solitary species of tuco-tuco (Rodentia: Ctenomyidae: Ctenomys), both of which occur in the same valley in southwestern Argentina. By comparing patterns of diversity at this MHC gene to the diversity evident at fifteen microsatellite loci, we demonstrate that balancing selection at the DQβ locus is enhanced in the social species compared to its solitary congener. These findings have intriguing implications for the role of behavioral and demographic parameters in maintaining diversity at MHC loci.

Corresponding Editor: S. Edwards