Summaries of the distribution of d_N/d_S ratios for the 202 loci analyzed in the four-species comparison. Rectangles surround the quantiles of the distribution (25-th, 50-th, and 75-th percentiles), with lines extending out to the 2.5-th and 97.5-th percentiles. (m/y) d_N/d_S between D. melanogaster and D. yakuba; (p/m) d_N/d_S between D. pseudoobscura and D. miranda.