The role of common ancestry and gene flow in the evolution of human-directed play behavior in dogs

Among-population variance of phenotypic traits is of high relevance for understanding evolutionary mechanisms that operate in relatively short timescales, but various sources of non-independence, such as common ancestry and gene flow can hamper the interpretations. In this comparative analysis of 138 dog breeds, we demonstrate how such confounders can independently shape the evolution of a behavioral trait (human-directed play behavior from the Dog Mentality Assessment project). We combined information on genetic relatedness and haplotype sharing to reflect common ancestry and gene flow, respectively, and entered these into a phylogenetic mixed model to partition the among-breed variance of human-directed play behavior while also accounting for within-breed variance. We found that 75% of the among-breed variance was explained by overall genetic relatedness among breeds, while 15% could be attributed to haplotype sharing that arises from gene flow. Therefore, most of the differences in h...