Mate choice and the major histocompatibility complex: a review

Abstract In many vertebrates, individuals choose mates due to benefits accrued via the production of offspring of high genetic quality. Genes of the major histocompatibility complex (MHC), which are associated with individual immunocompetence, provide potential benefits to choosers who mate with individuals that possess specific MHC alleles, have MHC genotypes dissimilar to their own, that are heterozygous for MHC loci, and/or are highly MHC-divergent. We review the evidence of these different modes of MHC mate choice, and the signals by which the MHC status of potential mates is assessed. MHC genes may directly or indirectly regulate individual odours, and thus enable MHC status assessment and mate choice via olfaction. For both visual and auditory signals, however, evidence of an association with MHC genes is relatively weak. Importantly, individual MHC status may be cotransmitted through multiple phenotypes, and different species may focus on different phenotypic signals due to differences in sensory sensitivity. Future research should focus on detecting phenotypic cues (including olfactory, visual, and auditory) that can signal MHC genotypes, as well as on investigating the underlying mechanisms of how MHC genes regulate these signals.