Morphological, genetic and behavioral comparisons of two prairie vole populations in the field and laboratory

Reports of geographic variation in behavior and morphology among prairie voles (Microtus ochrogaster) from Illinois, Kansas, and Tennessee have led to the belief that these animals vary in their mating strategies and the degree to which they are monogamous. Despite this, few studies have directly compared behavior between populations. Because the prairie vole is commonly discussed as a model for mammalian monogamy, understanding how aspects of social attachment and the mating system vary could provide further insight into the evolution of monogamy. We therefore conducted a series of experiments in the laboratory and field to assess morphological, behavioral, or genetic differences between 2 populations of this species. Voles from Illinois were morphologically similar to voles from Tennessee and exhibited comparable social and mating behavior under both laboratory and field conditions. Although genetically distinct, the 2 populations demonstrated similar levels of heterozygosity and allelic richness. Sexual dimorphism, a common indicator of mating strategy, was absent in voles from 7 widely distributed regions from across their geographic range. In the context of these results, we question the degree to which the previously described population differences are ecologically meaningful. If differences between prairie voles from Kansas and Illinois do indeed exist, examination of our data suggests that those from Kansas are atypical of prairie voles overall.