Frequencies of different forms of splice variation, arranged by phylogenetic group. The two bar charts show the relative frequencies of each type of splice variation. The ratio of CEs to RIs is shown in the chart on the left, while the one on the right displays competing 5' and competing 3' splice sites. Note that the CE/RI ratio shows wide variation among kingdoms while the ratio of competing 5' to competing 3' splice sites is remarkably consistent. A high-level overview of the phylogenetic tree is shown on the far left, and the organisms' names are colored according to their phylogenetic grouping. To see all four forms of splice variation on a single bar plot, see Additional data file 1. The data for H. sapiens was taken from a previous study .