Document Detail

Ecological genetics of adaptive color polymorphism in pocket mice: geographic variation in selected and neutral genes.
MedLine Citation:
PMID:  15266981     Owner:  NLM     Status:  MEDLINE    
Patterns of geographic variation in phenotype or genotype may provide evidence for natural selection. Here, we compare phenotypic variation in color, allele frequencies of a pigmentation gene (the melanocortin-1 receptor, Mc1r), and patterns of neutral mitochondrial DNA (mtDNA) variation in rock pocket mice (Chaetodipus intermedius) across a habitat gradient in southern Arizona. Pocket mice inhabiting volcanic lava have dark coats with unbanded, uniformly melanic hairs, whereas mice from nearby light-colored granitic rocks have light coats with banded hairs. This color polymorphism is a presumed adaptation to avoid predation. Previous work has demonstrated that two Mc1r alleles, D and d, differ by four amino acids, and are responsible for the color polymorphism: DD and Dd genotypes are melanic whereas dd genotypes are light colored. To determine the frequency of the two Mc1r allelic classes across the dark-colored lava and neighboring light-colored granite, we sequenced the Mc1r gene in 175 individuals from a 35-km transect in the Pinacate lava region. We also sequenced two neutral mtDNA genes, COIII and ND3, in the same individuals. We found a strong correlation between Mc1r allele frequency and habitat color and no correlation between mtDNA markers and habitat color. Using estimates of migration from mtDNA haplotypes between dark- and light-colored sampling sites and Mc1r allele frequencies at each site, we estimated selection coefficients against mismatched Mc1r alleles, assuming a simple model of migration-selection balance. Habitat-dependent selection appears strong but asymmetric: selection is stronger against light mice on dark rock than against melanic mice on light rock. Together these results suggest that natural selection acts to match pocket mouse coat color to substrate color, despite high levels of gene flow between light and melanic populations.
Hopi E Hoekstra; Kristen E Drumm; Michael W Nachman
Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Evolution; international journal of organic evolution     Volume:  58     ISSN:  0014-3820     ISO Abbreviation:  Evolution     Publication Date:  2004 Jun 
Date Detail:
Created Date:  2004-07-22     Completed Date:  2004-08-30     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  0373224     Medline TA:  Evolution     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1329-41     Citation Subset:  IM    
Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721, USA.
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MeSH Terms
Base Sequence
Cluster Analysis
DNA Primers
DNA, Mitochondrial / genetics
Gene Frequency
Genetic Variation*
Genetics, Population
Likelihood Functions
Models, Genetic
Molecular Sequence Data
Pigmentation / genetics*,  physiology
Receptor, Melanocortin, Type 1 / genetics
Rodentia / genetics*,  physiology
Selection, Genetic*
Sequence Analysis, DNA
Reg. No./Substance:
0/DNA Primers; 0/DNA, Mitochondrial; 0/Receptor, Melanocortin, Type 1

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