Genetic Diversity and Relatedness of Group-Living Small Mammals on the Mongolian Plateau

Genetic diversity plays an important role in the evolution and adaptation of organisms. Losses of genetic diversity make organisms more vulnerable to climate changes and diseases, reducing the viability of small populations. In addition to natural selection, genetic drift, dispersal, inbreeding, and population bottleneck, the social systems of animals may also affect the genetic diversity of populations. We aimed to test the hypothesis that the delayed dispersal of group-living small mammals would reduce genetic diversity through attenuated gene flow but enhance genetic relatedness. We used microsatellite analysis to estimate genetic diversity and the Queller and Goodnight relatedness coefficients of Daurian pikas (Ochotona dauurica) and Mongolian gerbils (Meriones unguiculatus), two socially monogamous small mammals living in social groups in Inner Mongolia, China. The average genetic relatedness of social groups was inversely related to the average genetic diversity of social groups in Daurian pikas but not in Mongolian gerbils, partially supporting our hypothesis. Dispersal following frequent local extinctions resulted in the recolonization of burrow systems by individuals with different genetic makeups, increasing genetic diversity and reducing the genetic relatedness of the social groups of Daurian pikas. On the other hand, delayed short-distance dispersal was sufficient to maintain the high genetic diversity and high genetic relatedness of gerbil social groups independently.