Social and paternal female choice for male MHC genes in golden snub-nosed monkeys (Rhinopithecus roxellana)

Genes of the major histocompatibility complex (MHC) play important roles in vertebrate immunocompetence. MHC genes thus offer females indirect benefits to mate choice through the production of offspring of an optimal MHC genotype. Females may choose males with specific MHC haplotypes, dissimilar MHC genotypes, MHC heterozygous males or MHC-diverse males. We tested these four alternatives for both female social and paternal choice in wild golden snub-nosed monkeys (Rhinopithecus roxellana) by examining overall genetic variability (via microsatellites) and four MHC-genes (DRB1, DRB2, DQA1 and DQB1). Monte Carlo randomization tests showed that MHC dissimilarity was favoured for social choice (males to which females were socially affiliated) and intermediate MHC dissimilarity was favoured in paternal choice (fathers of offspring). No evidence of inbreeding avoidance was found for either social or paternal mates. We found that MHC heterozygotes, higher microsatellite multilocus heterozygosity and higher microsatellites diversity were favoured for social mates, and higher microsatellite diversity was favoured for paternal mates. Independent of male age, we found that the formation of male-female social pairings is significantly predicted by compatibility based on the sharing of MHC haplotypes. However, we found no evidence of independent genetic effects on the duration of male-female social pairings, male social status (achieving OMU leader male status or not), the number of females with which individual leader males paired, the likelihood of potential male-female pairings producing offspring, or whether males fathered offspring or not. Overall, our findings suggest different genetic factors are involved in social and paternal choice in R. roxellana.