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Sociality in subterranean rodents
Of the 19 genera of rodents that are typically recognized as subterranean, only 5 are known to contain species in which adults of one or both sexes routinely share burrow systems. I am using comparative field studies of two group-living species, the colonial tuco-tuco (Ctenomys sociabilis) and the coruro (Spalacopus cyanus) to explore the ecological bases of sociality in these animals. By combining data from these two South American rodents with published information from social African mole-rats, I am building a comprehensive picture of the extent to which group living in these biogeographically and phylogenetically distinct taxa reflects shared versus taxon-specific ecological factors.

Population genetics of subterranean rodents
In addition to documenting the ecology of group living in subterranean rodents, I am exploring how sociality influences the population genetic structure of these animals. Using data from both microsatellite and mtDNA sequence analyses, I am quantifying patterns and levels of neutral genetic diversity in the group-living colonial tuco-tuco (Ctenomys sociabilis) and the solitary Patagonian tuco-tuco (C. haigi), both of which occur in the Limay River Valley in southwestern Argentina. In collaboration with former graduate student Tina Hambuch, I am also characterizing variation at Major Histocompatibility Complex (MHC) loci in these species. Collectively, these analyses are revealing striking interspecific differences in genetic structure that appear to reflect current behavioral and demographic differences between these taxa.

Interspecific variation in ground squirrel mating systems
My past work concerned studies of ground squirrel mating systems, which provide a rich source of comparative data regarding relationships between behavior, ecology, and reproductive success. A growing body of evidence indicates that sperm competition and the resulting patterns of sperm precedence may play an important role in shaping male behavior. Through my own studies of arctic ground squirrels and collaborative analyses of paternity and sperm precedence in other species of Spermophilus, I am working to identify potentially causal relationships between patterns of fertilization success and male reproductive competition in these animals.