πN/πS ratios for mtDNA protein-coding genes. The πN/πS ratios for ten mtDNA protein-coding genes were calculated for the temperate-clade (black bars, n = 11) and tropical-clade (white bars, n = 11) C. briggsae isolates. Ratios were not calculated for two mtDNA genes because no nonsynonymous substitutions were observed for ND4L and COII in the temperate and tropical isolates, respectively. Concatenated protein-coding gene data files (12 genes) were also analyzed in the temperate and tropical-clade isolates, as well as in a set of C. elegans (dashed bar, n = 17) isolates.
Howe and Denver BMC Evolutionary Biology 2008 8:62 doi:10.1186/1471-2148-8-62