Philopatry, kin clusters, and genetic relatedness in a population of woodrats (Neotoma macrotis)

Studies of highly kin-structured mammal societies have revealed the importance of natal philopatry in determining the distribution of genetic variation within populations. In comparison, the relationship between philopatry and genetic diversity within populations of moderately kin-structured societies has received relatively little attention. Previous studies of Neotoma macrotis have suggested that females form distinct kin clusters. Each kin cluster overlaps spatially with the home range(s) of one or more males that are not related to each other or to the females with which they are spatially associated. To examine interactions between philopatry and genetic structure in this apparently moderately kin-structured species, we characterized spatial and genetic relationships among individually marked females in a population of N. macrotis from central coastal California. Our field studies revealed that, contrary to expectation, females in this population were not strongly philopatric and spatially clustered females were not characterized by high levels of genetic relatedness. Nevertheless, genetic structure was evident within the study population; spatial and genetic distances among females were significantly correlated, suggesting that dispersal patterns influenced genetic structure even in the absence of marked female philopatry. Because females with overlapping spatial distributions were not typically closely related to one another, opportunities for the evolution of kin-selected social behavior (e.g., cooperative care of young) appear to be limited in this population.