Genetic structure of a metapopulation of black-tailed prairie dogs

Habitat alteration, agricultural control, recreational shooting, and most r ecently, sylvatic plague (caused by Yersinia pestis) contributed to local e xtinctions and a steady decline of black-tailed prairie dog (Cynomys ludovi cianus) throughout its range. As a consequence, prairie dogs currently live in metapopulations, where their overall persistence will depend on a balan ce between extinction of colonies and recolonization from extant colonies. Patterns of genetic similarity among colonies, as measured by neutral molec ular markers, provide an estimate of the dispersal and gene flow among colo nies within prairie dog metapopulations. We sampled 13 colonies of black-ta iled prairie dogs in short-grass prairie of northern Colorado, 100-km east of Fort Collins, Colorado. We used historical records and genetic analysis to show that colonies undergo regular extinctions, which subsequently are r ecolonized by individuals from multiple source colonies. We examined 155 in dividuals for variation at 7 microsatellite loci and found moderate levels of genetic differentiation among colonies (Theta [= F-ST] = 0. 118). We als o used assignment and exclusion tests based on multilocus genotypes of indi viduals to determine the probability that individuals originated from the s ame colony in which they were captured. About 39% of individuals could not be assigned to colonies where they were captured, indicating they were eith er immigrants (adults) or the offspring of immigrants (adults and juveniles ). We tested for genetic isolation by distance among colonies by comparing genetic distances to geographic distances between colonies. Akaike's Inform ation Criterion for model selection revealed that dispersal most likely occ urred along low-lying dry creek drainages connecting isolated colonies. Gen etic distances between colonies were also related to ages of colonies; olde r colonies were more similar genetically than younger colonies. This unders cores the importance of dispersal among prairie dog colonies and has import ant implications for persistence of prairie dog metapopulations, in which a ll colonies, regardless of size, are vulnerable to extinction from plague.