SREL Reprint #2193

Do black-tailed prairie dogs minimize inbreeding?

F. Stephen Dobson1, Ronald K. Chesser2,3, John L. Hoogland4, Derrick W. Sugg5, and David W. Foltz6

1Department of Zoology and Wildlife Science, and Alabama Agricultural Experimental Station,
Auburn University, Auburn, Alabama 36849
2University of Georgia, Savannah River Ecology Laboratory, Aiken, South Carolina 29802
3Department of Genetics, University of Georgia, Athens, Georgia 30602
4Appalachian Environmental Laboratory, University of Maryland, Frostburg, Maryland 21532
5Department of Biology, State University of New York, Geneseo, New York 14454
6Department of Zoology and Physiology, Louisiana State University, Baton Rouge, Louisiana 70803

Abstract: Considerable controversy surrounds the importance of inbreeding in natural populations. The rate of natural inbreeding and the influences of behavioral mechanisms that serve to promote or minimize inbreeding (e.g., philopatry vs. dispersal) are poorly understood. We studied inbreeding and social structuring of a population of black-tailed prairie dogs (Cynomys ludovicianus) to assess the influence of dispersal and mating behavior on patterns of genetic variation. We examined 15 years of data on prairie dogs, including survival and reproduction, social behavior, pedigrees, and allozyme alleles. Pedigrees revealed mean inbreeding coefficients (F) of 1-2%. A breeding-group model that incorporated details of prairie dog behavior and demography was used to estimate values of fixation indices (F-statistics). Model predictions were consistent with the minimization of inbreeding within breeding groups ("coteries," asymptotic FIL = -0.18) and random mating within the subpopulation ("colony," asymptotic FIS = 0.00). Estimates from pedigrees (mean FIL = -0.23, mean FIS = 0.00) and allozyme data (mean FIL = -0.21, mean FIS = -0.01) were consistent with predictions of the model. The breeding-group model, pedigrees, and allozyme data showed remarkably congruent results, and indicated strong genetic structuring within the colony (FLS = 0.16, 0.19, and 0.17, respectively). We concluded that although inbreeding occurred in the colony, the rate of inbreeding was strongly minimized at the level of breeding groups, but not at the subpopulation level. The behavioral mechanisms most important to the minimization of inbreeding appeared to be patterns of male-biased dispersal of both subadults and adults, associated with strong philopatry of females. Incest avoidance also occurred, associated with recognition of close kin via direct social learning within the breeding groups.

Keywords: Cynomys, F-statistics, gene diversity, gene dynamics, inbreeding, social behavior

SREL Reprint #2193

Dobson, F.S., R.K. Chesser, J.L. Hoogland, D.W. Sugg, and D.W. Foltz. 1997. Do black-tailed prairie dogs minimize inbreeding? Evolution 51:970-978.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).