Genetic variance and indirect genetic effects for affiliative social behavior in a wild primate

Abstract

Affiliative social behaviors are linked to fitness components in multiple species. However, the role of genetic variance in shaping affiliative social behaviors remains largely unknown, limiting our understanding of how these behaviors can respond to natural selection. Here, we employed the animal model to estimate both environmental and genetic sources of variance and covariance in grooming behavior in the well-studied Amboseli baboon population in Kenya. We found that grooming given, grooming received, and total grooming all are similarly heritable (h2=0.22, h2=0.16, and h2=0.26 respectively), and that rank and the presence of kin contribute to environmental variance. We detected small but measurable indirect genetic effects of partner identity on the amount of grooming given within dyadic grooming partnerships. The genetic correlation between grooming given and grooming received was exceptionally strong and positive (R=0.94 {+/-} 0.12), and the indirect and direct genetic effects for grooming given were also strongly positively correlated (R=0.86 {+/-} 0.06). Our results provide insight into the evolvability of affiliative behavior in wild animals, including the possibility for correlations between direct and indirect genetic effects to accelerate the response to selection. As such they provide novel information about the genetic architecture of social behavior in nature, with important implications for the evolution of cooperation and reciprocity.