An MHC component to kin recognition and mate choice in birds: predictions, progress, and prospects

The major histocompatibility complex (Mhc) has been identified as a locus influencing disease resistance, mate choice, and kin recognition in mammals and fish. However, it is unclear whether the mechanisms by which Mhc genes influence behavior in mammals are applicable to other nonmammalian vertebrates such as birds. We review the biology of Mhc genes with particular reference to their relevance to avian mating and social systems. New genomics approaches recently have been applied to the Mhcs of chickens, quail, and several icons of avian behavioral ecology, including red-winged blackbirds (Agelaius phoeniceus) and house finches (Carpodacus mexicanus). The predominance of concerted evolution at avian Mhc loci makes such methods attractive for providing access to this complicated multigene family. Although some biological processes influenced by Mhc in mammals are physiologically implausible for birds, Mhc could influence cues that form well-known bases for mate choice in birds by influencing the health and vigor of individuals. The tight associations of Mhc variation and disease resistance in chickens raise hope that finding associations of Mhc genes, disease, and mate choice in natural populations of birds will be as fruitful as in mammalian systems.