28.5 Wednesday, Jan. 4 The evolution of Mc1R in the snake genus Sonora COX, Christian L.*; DAVIS RABOSKY, Alison R.; CHIPPINDALE, Paul T.; The University of Texas, Arlington; The University of California, Berkeley; The University of Texas, Arlington firstname.lastname@example.org
Color pattern polymorphism (CPP) presents an interesting puzzle in evolutionary biology. Because genetic drift will fix neutral alleles over time, the persistence of polymorphism must be explained by additional neutral (e.g., drift with gene flow) or selective (e.g., frequency dependent selection) processes. Understanding how this polymorphism is generated and maintained in natural populations is integral to understanding basic evolutionary processes such as aposematism, sexual selection, and speciation. An excellent system for studying CPP is the ground snake (Sonora semiannulata) which has four different dorsal color patterns that vary in frequency across their geographic range. A powerful method for understanding CPP is to examine genetic loci underlying color pattern for the signature of selection. One gene (Mc1R) has emerged as a particularly important single gene underlying the genetic architecture of color pattern (specifically melanin) in many vertebrates. We examined the Mc1R sequence across the geographic range of S. semiannulata, among all other species of Sonora, and two sister genera (Chilomeniscus and Chionactis) that are also polymorphic. We found that the entire Mc1R coding region is variable among Chilomeniscus, Chionactis, and Sonora (approximately 4% sequence divergence). Relative to an outgroup (Thamnophis sirtalis), there is a large (12 bp) indel common to all included taxa, with a separate 6bp indel present in only one Sonora species. Future association tests between amino acid substitutions and color pattern will test whether the considerable sequence variation in Mc1R within Sonora is important for CPP in these snakes. These results will help further understanding of how selective and neutral forces maintain polymorphism in natural populations.