Reduced Selection for Codon Usage Bias in Drosophila miranda
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Biased codon usage in many species results from a balance among mutation, weak selection, and genetic drift. Here I show that selection to maintain biased codon usage is reduced in Drosophila miranda relative to its ancestor. Analyses of mutation patterns in noncoding DNA suggest that the extent of this reduction cannot be explained by changes in mutation bias or by biased gene conversion. Low levels of variability in D. miranda relative to its sibling species, D. pseudoobscura, suggest that it has a much smaller effective population size. Reduced codon usage bias in D. miranda may thus result from the reduced efficacy of selection against newly arising mutations to unpreferred codons.
KeywordsCodon bias Drosophila miranda Reduced selection
I am grateful to Peter Andolfatto and Brian Charlesworth for comments on the manuscript. This work was funded by National Institutes of Health Grant GM076007 to D.B.