Fig. 3

Lengths of exons and introns in order. The seven species are displayed in a phylogenetic order with unscaled branch length. The four columns represent the genes with two, six, ten, and 20 exons, respectively. Exons and introns are displayed in order (from 5’ to 3’). Exons are in red and introns are in blue. Last exons are significantly longer than other exons in all cases, P < 0.001, Wilcoxon rank sum tests. The decrease of intron length is measured by Spearman correlation test. We obtained P < 0.001 in all cases with at least five introns