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Summary: The genetic basis of adaptive melanism in
pocket mice
Michael W. Nachman*, Hopi E. Hoekstra, and Susan L. D'Agostino
Department of Ecology and Evolutionary Biology, Biosciences West Building, University of Arizona, Tucson, AZ 85721
Communicated by Margaret G. Kidwell, University of Arizona, Tucson, AZ, February 26, 2003 (received for review December 17, 2002)
Identifying the genes underlying adaptation is a major challenge in
evolutionary biology. Here, we describe the molecular changes
underlying adaptive coat color variation in a natural population of
rock pocket mice, Chaetodipus intermedius. Rock pocket mice are
generally light-colored and live on light-colored rocks. However,
populations of dark (melanic) mice are found on dark lava, and this
concealing coloration provides protection from avian and mam-
malian predators. We conducted association studies by using
markers in candidate pigmentation genes and discovered four
mutations in the melanocortin-1-receptor gene, Mc1r, that seem to
be responsible for adaptive melanism in one population of lava-
dwelling pocket mice. Interestingly, another melanic population of
these mice on a different lava flow shows no association with Mc1r
mutations, indicating that adaptive dark color has evolved inde-
pendently in this species through changes at different genes.
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