The primary objective of the proposed research is to identify mutations responsible for naturally occurring coat-color variation in populations of light and dark rock pocket mice that live on light and dark substrates. In particular, the proposed research will (1) document variation in coat color of mice and environmental heterogeneity in soil color for six paired localities in New Mexico and Arizona where each pair consists of one light and one dark locality, (2) conduct a screen to identify genes contributing to the observed phenotypic differences, (3) characterize mutant alleles at the loci implicated in phenotypic differences, and (4) characterize genetic variation at coat-color loci in population samples from dark and light localities. Together, these studies will (1) identify the number and relative effects of different genes contributing to coat color variation, (2) determine whether pigmentation differences are due primarily to structural changes, regulatory changes, or both, (3) determine whether dark coat-color has evolved independently in different populations, and if it has, determine whether the same or different mutations are involved, and (4) determine the extent to which selection at one site in the genome has shaped patterns of genetic variation at linked neutral sites. A central goal in biology is to explicitly connect genotype with phenotype for traits that are ecologically important. This has been an elusive goal because the genetic basis of most traits is not well understood. Coat-color variation in rodents is a classic example of phenotypic variation in response to local adaptation: in many species, dorsal pelage color closely matches the color of the soil on which the animals live. A century of research on the genetics of coat color in house mice has produced a rich database of candidate genes and mutant effects. The combination of striking phenotypic variation in coat-color of pocket mice (Chaetodipus intermedius) and candidate pigmentation loci cloned in the laboratory mouse presents an unparalleled opportunity to investigate the genetic variation underlying a key morphological trait in nature.
