Mammalian melanism: natural selection in black and white

Two recent papers on the molecular basis of melanism strengthen the chain of evidence linking genotype and phenotype in nature. Research on coat colour polymorphisms in rock pocket mice from differently coloured rock substrates provides a compelling example of the genetics of adaptation and the serendipitous nature of darwinian selection. Mutations in one gene, melanocortin-1-receptor, are perfectly associated with dark coat colour on black lava. Comparative sequence analysis shows that the same gene is involved in melanic polymorphism in some cats.