Do relatives like to stay closer? Spatial organization and genetic relatedness in a mountain roe deer population

The fine-scale genetic structure of mammal populations arises from the social and spatial behaviour of individuals. In wild ungulates gene flow is usually mediated by males, being the dispersing sex. The roe deer Capreolus capreolus represents an exception: males and females disperse in similar proportions as juveniles, but are subsequently mostly sedentary as adults, while mechanisms for inbreeding avoidance are more complex and not fully known. We investigated the seasonal variation in the relationship between genetic relatedness and spatial behaviour in a sample of 69 roe deer, monitored from 2002 to 2010 in a high-density population in Italy. Genetic and spatial analyses, based on individual positions, did not reveal any population structure, neither in the whole sample, nor in the two sexes separately. Our results are coherent with the absence of a sex bias in roe deer dispersal and suggest the existence of a high gene flow across a continuous forest habitat, thus preventing the onset of population structuring at a local scale. We found that genetic relatedness tended to increase with home range proximity, but mostly in winter. Nevertheless, when the extent of overlap between seasonal home ranges with respect to genetic relatedness was considered, males and females seemed to preferably share their home range with relatives of the same sex, reducing the overlap with relatives of the opposite sex during the rutting period. We conclude that home range rearrangements during the breeding season may afford a certain level of spatial segregation between closely related potential mates, thus reducing inbreeding risk.