Mean divergences for non-synonymous sites, synonymous sites and both small and large introns. Mean levels of divergence between D. melanogaster and D. simulans for non-synonymous and synonymous sites of coding data, introns ≤86 bp and introns >86 bp. Error bars indicate two standard errors. Synonymous site divergence is significantly greater than large (Wilcoxon two-sample test statistic W = 7745.5, P < 10-4) but not small (W = 15115.5, P = 0.6173) intron divergences. Small intron divergence is significantly greater than large intron divergence (W = 17079.5, P < 10-4).