Fine-scale spatial organization reflects genetic structure in sheep

Preferential spatial associations between related animals have been reported in several species, but whether these relationships extend to fine resolution is largely unknown. Using a novel approach that combined pedigrees and precise geographic locations, we tested the relationship between extremely fine-scale (< 3 m) spatial structure and relatedness within a captive flock of domestic female Dorset sheep (Ovis aries). Using GPS, we recorded the spatial distribution of individuals while foraging on summer pasture; we compared this to pair-wise coefficients of relatedness (r) and assessed significance of the patterns using Mantel and partial Mantel tests. Population organization was discernible even at this fine spatial resolution. Closely related ewes, especially full- and half-siblings (r >= 0.25), formed closer spatial associations than lesser-related and unrelated pairs. The genetic structuring of the flock provides a potential platform for kin selection and suggests that random population organization may not exist even at the finest spatial scales.