Citation:
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Abstract:
In a series of classic studies in mammalian evolutionary biology, Sumner (1921), Benson (1933), and Dice and Blossom (1937) described striking coat color variation in the rock pocket mouse, Chaetodipus intermedius, in the deserts of Arizona and New Mexico. These authors showed that C. intermedius coat color typically matches the color of the rocks on which the mice live; the dorsal pelage varies from a light, sandy color for populations found on some granites to a dark, nearly black color for populations found on basalt lava flows. Dice and Blossom (1937) suggested that this crypsis is an adaptation to avoid predation. Motivated by the wealth of data on the genetics, biochemistry, and molecular biology of the pigmentation process, we have used a candidate-gene approach to identify the genetic basis of adaptive coat color variation in C. intermedius. We review our recent studies on this topic with emphasis on the following key results: the identification of a single gene (the melanocortin-1-receptor, Mc1r) in one population that appears to be largely responsible for color differences, the balance between selection and migration among neighboring melanic and light races, and the finding that melanism has evolved independently on different lava flows through changes at different genes.