Cumulative distribution of CAI for each chromosome arm. In the lower right of each pane are the chromosomes arm and the Muller/Sturtevant element names for each species. U stands for genes of unknown location. The 5th chromosome in Dpse (Element F) is not identified yet from the contigs and genes on it are likely included in the U group. The ragged distribution of the U group genes in Dpse is probably due to the mixed effect of F element genes and those on other elements. ANOVA indicates that element F genes (U group genes were used for Dpse) are significantly less biased and element A genes more biased with p < 10-15 for all four species.