A window on the genetics of evolution: MC1R and plumage colouration in birds.

Melanins are a ubiquitous component of plumage colouration in birds and serve a wide variety of functions. Although the genetic control of melanism has been studied in chickens and other domestic species, little was known about the molecular genetics of melanin distribution in wild birds until recently. Studies have now revealed that a single locus, the melanocortin-1 receptor (MC1R) locus, is responsible for melanic polymorphisms in at least three unrelated species: the bananaquit, the snow goose and the arctic skua. Results show that melanism was a derived trait and allow other evolutionary inferences about the history of melanism to be made. The role of MC1R in plumage patterning is surprisingly diverse among different species. The conserved molecular basis for the evolution of melanism in birds and several other vertebrates is probably related to low pleiotropic effects at the MC1R.