Multiple mechanisms for inbreeding avoidance used simultaneously in a wild ape

Abstract

Mating with close kin can have considerable negative fitness consequences, which are expected to result in selective pressure for inbreeding avoidance mechanisms, such as dispersal, mate choice and post-copulatory biases. Captive studies have suggested that inbreeding avoidance through mate choice is far less widespread than expected and may be absent where other mechanisms already limit inbreeding. However, few studies have examined multiple mechanisms of inbreeding avoidance simultaneously, particularly in the wild. We use 13 years of detailed dispersal, copulation and paternity data from mountain gorillas to examine inbreeding avoidance. We find that partial dispersal of both sexes results in high kinship in multimale groups, but that copulations between close kin occur 40% less than expected. We find strong kin discrimination in mate choice, with significant avoidance of maternal kin but more limited avoidance of paternal kin. We find no evidence for post-copulatory inbreeding avoidance. Our analyses support familiarity-based mechanisms of kin identification and age-based avoidance that limits mating between fathers and daughters in their natal group. Our findings demonstrate that multiple complementary mechanisms for inbreeding avoidance can evolve in a single species and suggest that inbreeding avoidance through mate choice may enable more flexible dispersal systems to evolve.

Male‐philopatric nonhuman primates and their potential role in understanding the evolution of human sociality

“…), both sexes are known to regularly disperse from their natal groups despite the fact that members of both sexes have also been documented remaining in their natal groups. [35][36][37][38] A study of western gorillas (Gorilla gorilla) found that males do not travel as far as females, 39 causing them to be categorized as female-biased dispersers. However, studies in both western gorillas and mountain gorillas (Gorilla beringei beringei), have found evidence of males having a longer dispersal distance.…”

“…Early hominin social groups are hypothesized to be based on male kin alliances, 146 but is a topic of debate. 38,[147][148][149][150] Male philopatry in the last common ancestor of Pan and hominins would also have created conditions for strong male social bonds and cooperative behaviors throughout human evolution. 60,90 As previously discussed, kin selection is not the only driver of male cooperation seen in malephilopatric groups, and thus, other evolutionary mechanisms (e.g., familiarity) must be involved.…”

“…For example, in gorillas ( Gorilla spp. ), both sexes are known to regularly disperse from their natal groups despite the fact that members of both sexes have also been documented remaining in their natal groups 35–38 . A study of western gorillas ( Gorilla gorilla ) found that males do not travel as far as females, 39 causing them to be categorized as female‐biased dispersers.…”

“…Early hominin social groups are hypothesized to be based on male kin alliances, 146 but is a topic of debate 38,147–150 . Male philopatry in the last common ancestor of Pan and hominins would also have created conditions for strong male social bonds and cooperative behaviors throughout human evolution 60,90 .…”