Behavior, Demography, and Immunogenetic variation: new insights from subterranean rodents

EILEEN LACEY; ANA PAULA CUTRERA

Subterranean rodents: News from Underground

Springer-Verlag

Lugar: Berlin; Año: 2007; p. 341 - 355

Understanding how selection acts to shape genotypic variation is a fundamental goal of evolutionary research. The genes of the Major Histocompatibility Complex (MHC) provide a particularly appropriate system for exploring this topic because they tend to be highly variable, subject to strong selection, and relatively well understood with regard to their role in detection of and response to pathogens. Although the apparent link between pathogen exposure and MHC variation suggests that selection at these loci should vary predictably in response to behavioral and demographic attributes, few studies have explored patterns or processes of MHC diversification in natural populations of non-human mammals. Here, we report on recent analyses of MHC variation in subterranean rodents that are yielding new insights into relationships between population structure (e.g., density, social system) and selection at MHC loci. In particular, our on­going studies of the population biology and genetic structure of three species of tuco-tucos (Rodentia: Ctenomyidae: Ctenomys) indicate that behavioral and demographicc variation is associated with significant differences in the patterns and strengths of selection at three MHC Class II loci. Specifically, comparisons of genetic structure in the solitary Patagonian tuco-tuco (C.haigi) and the group-living colonial tuco-tuco (C. sociabilis) indicate that selection on two loci (DQB and DRB) is stronger in the social species, as expected if sociality results in increased transmission of pathogens among conspecifics. At the same time, analyses of genetic structure in the talar tuco-tuco (C. talarum) have revealed that, among populations, the strength of selection on two MHC loci (DRB and DQA) varies with density, a primary correlate of patho­gen exposure. Collectively, these analyses suggest that behavior and demography are important determi­nants of selection for increased immunogenetic variation. We outline several directions for future studies of subterranean rodents aimed at clarifying causal connections between population structure, pathogen exposure, and selection on MHC loci.