BREEDING GROUPS AND GENE DYNAMICS IN A SOCIALLY STRUCTURED POPULATIONOF PRAIRIE DOGS

Genetic substructuring of a colony of black-tailed prairie dogs (Cynom ys ludovicianus) was examined using three different sources of informa tion: allozyme alleles, pedigrees, and demography (a ''breeding-group' ' model based on mating and dispersal patterns). Prairie dogs and thei r social breeding groups (called ''coteries'') were studied under natu ral conditions during a 15-year period. Prairie-dog coteries exhibited substantial genetic differentiation, with 15-20% of the genetic varia tion occurring among coteries. Mating patterns within the colony appro ximated random mating, and, thus, mates tended to originate from diffe rent coteries. Social groups of black-tailed prairie dogs resulted in genetic substructuring of the colony, a conclusion that was supported by estimates from allozyme alleles and colony pedigrees. Predictions o f the breeding-group model also were consistent with and supported by estimates from allozyme and pedigree data. Some methodological problem s were revealed during analyses. Although individuals of all ages usua lly are pooled for biochemical estimates of among-group genetic differ entiation, our estimates of among-coterie variation from allozyme data were somewhat higher for young than for older prairie dogs, perhaps d ue to sampling effects caused by mating patterns and infanticide of of fspring. Pedigree estimates of among-coterie genetic differentiation w ere significantly positive for young prairie dogs, adult females, and adult males. Those estimates were always more accurate for the offspri ng generation, however because pedigree data were always more complete for young and genetic differences among coteries were diluted by virt ually complete dispersal of males away from their natal coteries.