Number of fixed synonymous and non-synonymous interspecific differences between representative species pair comparisons for Pgi (1356 bp) and Pgm (441 bp).

Note the difference in sequence length between Pgi and Pgm (see π in Table 1). Estimates for D. melanogaster and D. simulans are provided for comparison (synonymous site divergence for this pair is similar to the maximum distance between Bombus pairs – see text). Comparisons were made between pairs of subgeners (B. pascuorum & B. humilis; B. pratorum & B. monticola) as well as an arbitrary selection of common species pairs to illustrate the full range of differences observed. The lack of intraspecific differences observed precludes McDonald-Kreitman (30) tests of selection in most cases.