Mechanisms of Inbreeding Avoidance in a Wild Primate

Abstract

The deleterious effects of inbreeding have been well-documented in both captive and wild populations. Mechanisms of inbreeding avoidance such as mate choice and sex-biased dispersal have also been documented across a variety of taxa. However, studies of inbreeding avoidance via mate choice are surprisingly scarce, and those that explicitly compare maternal and paternal kin are entirely absent in mammals. Here, we provide the first study to assess how behavioral inbreeding avoidance varies across kin classes in a population of wild baboons. We first examine the series of isolating barriers that prevent inbreeding, including death, dispersal, and mate choice, and we next use pedigree data to assess how behavioral inbreeding avoidance varies across kin classes. We found that while the demographic barriers of death and male-biased dispersal are extremely effective in limiting inbreeding in this population, we still found strong evidence for inbreeding avoidance via mate choice. In particular, while most kin classes exhibited inbreeding avoidance, maternal kin (mother-son pairs, maternal siblings) were more avoidant than paternal kin (father-daughter pairs, paternal siblings) despite having identical coefficients of relatedness. Finally, by taking advantage of a natural experiment in our study population, we also found that social groups with reduced sex-biased dispersal and reduced inbreeding avoidance via mate choice produced ten times as many inbred offspring.