A molecular genetic analysis of social system dynamics and population structure in Gunnison's prairie dog

The purpose of this study was to provide insights into the nature and importance of the interaction between social and genetic forces as they pertain to species evolution, using Gunnison's prairie dog (Cynomys gunnisoni) as a model system. These animals are colonial and group territorial, with social groups consisting of several adults of each sex and their immature offspring.; A combination of field and laboratory techniques were used to compare two prairie dog colonies near Flagstaff, Arizona. Live-trapping and observational procedures were conducted within 1.44 hectare study plots during 1988 through 1992, in order to assign individuals to territories. Blood samples were collected from captured animals during 1991, in order to construct DNA fingerprints from which genetic relationships could be deduced.; An investigation of mating system control revealed that females were controlling the mating system by actively seeking to copulate with extraterritorial males. This was concluded from the following: first, 61% of all juveniles were found to be the offspring of extraterritorial males; second, intermale aggression is known to severely restrict the interterritorial movements of adult males, but not of females.; An investigation of inbreeding was undertaken on the basis of preliminary results suggesting unusually low levels of genetic heterozygosity within the two populations studied. It was hypothesized that populations at low densities would display inbreeding in order to maintain local adaptations, while populations at high densities would display outbreeding as a means of increasing genetic heterozygosity. These predictions were supported, and were correlated with several ecological factors.; An investigation of population structure revealed a significant level of subdivision, as predicted on the basis of the historical prevalence of sylvatic plague, as well as the existence of apparent barriers to dispersal. A statistically significant value of Wright's F{dollar}sb{lcub}rm ST{rcub}{dollar} was revealed which was similar to values reported from other studies of social North American ground squirrels.; Finally, an attempt was made to model the social system on the basis of ecological and demographic forces. Plant patchiness and population density were used to predict social group size and composition, as well as mate choice relative to inbreeding. This model was supported in its predictions.