Do Black-Tailed Prairie Dogs Minimize Inbreeding?

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 F = -0.18) and random mating within the subpopulation ("colony," asymptotic F = 0.00). Estimates from pedigrees (mean F = -0.23, mean F = 0.00) and allozyme data (mean F = -0.21, mean F = -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 (F = 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.

Sex-Biased Dispersal in a Migratory Bat: A Characterization Using Sex-Specific Demographic Parameters

“…In the blacktailed prairie dog (Cynomys ludovicianus), it has been shown using Chesser's models (Chesser 1991a,b;Chesser et al 1993) that male dispersal associated with polygyny leads to the formation of high coancestry levels with negligible inbreeding (Sugg et al 1996;Dobson et al 1997). Such a situation makes the evolution of sociality possible without having to pay the costs of inbreeding depression.…”

The evolutionary ecology of the major histocompatibility complex

“…Such models need to incorporate not only variation in population size and levels of dispersal but also variation in social structure within populations. In the broader field of population genetics, there is increasing emphasis on determining the extent of social affiliation within populations (Dobson et al, 1997Girman et al, 1997;Dobson, 1998;Piertney et al, 1999) and on developing a framework to model neutral gene dynamics in socially structured populations (Chesser, 1991a, b;Sugg and Chesser, 1994;Sugg et al, 1996). Understanding how social structure affects MHC dynamics may be especially important given that social structure will influence the transmission of parasites and disease at a local scale, and also the potential for mate choice decisions will vary in response to levels of local inbreeding.…”

Kin selection in Columbian ground squirrels ( Urocitellus columbianus ): littermate kin provide individual fitness benefits

“…They are relatively long lived (up to about 10 years old), and generation overlap (both spatial and temporal) allows for the presence of matrilineal kin and the occurrence of nepotistic behaviours (King & Murie 1985;King 1989a). Female philopatry produces kin associations that may result in both competition and cooperation among relatives (Dobson et al 1997;Dobson 1998; for a review, Lawson Handley & Perrin 2007). Females exhibit territoriality (Murie & Harris 1978, 1988 and kindifferential behaviours, namely reduced aggressiveness and increased tolerance of close maternal kin (King 1989b).…”