Genetic and spatial structure within a swift fox population

1. We incorporated spatial data on swift foxes (Vulpes velox) with genetic analysis to assess the influence of relatedness between individuals on their social and spatial ecology. We recorded the space use patterns of 188 radio-collared swift foxes in south-eastern Colorado from January 1997 to December 2000. One hundred and sixty-seven foxes were also genotyped at 11 microsatellite DNA loci and the degree of relatedness between individuals was estimated. 2. We described the genetic structure of the population by examining the relatedness of neighbours and the relationship between the spatial and genetic distance of all individuals. We found that close kin appeared to cluster within the population. Neighbours were significantly more related (mean R = 0.089 +/- 0.01) than non-neighbours (mean R = 0.003 +/- 0.01; randomization test, P < 0.0002). Female clusters were more extensive than male clusters. 3. The degree of genetic relatedness among foxes was useful in explaining why foxes tolerated encroachment of their home ranges by neighbours; the more closely related neighbours were, the more home-range overlap they tolerated (Mantel test, P = 0.0004). Foxes did not appear to orientate their home ranges to avoid neighbours and home ranges overlapped by as much as 54.77% (x = 14.13% +/- 0.41). Neighbours also occasionally engaged in concurrent den sharing. 4. Relatedness influenced the likelihood that an individual would inherit a newly vacated home range, with a mean relatedness of range inheritors to previous owners of 0.333 +/- 0.074. Thus, the genetic structure of the population and interactions between kin were interrelated to space-use patterns and social ecology of the swift fox.