Figure 2From: Similar rates of protein adaptation in Drosophila miranda and D. melanogaster, two species with different current effective population sizesAn excess of rare polymorphisms and reduced codon bias in fast evolving protein-coding genes. A. Tajima's D, a measure of the frequency distributions of mutations, is plotted against the rate of amino-acid evolution (Ka) at X-linked loci in D. miranda. B. The frequency of optimal codons (Fop) is plotted against the rate of amino-acid evolution (Ka).Back to article page