Fig. 2

Lengths and GC contents of exons and introns. The seven species are displayed in a phylogenetic order with unscaled branch length. Exon and intron lengths are shown with a log₂(length + 1) transformation. The X-axis is the number of exons/introns per gene. That means, the exon/intron lengths (Y-axis) are grouped within these genes (each group is a box) and displayed separately in the boxplot. Spearman’s correlation is calculated for each plot. The statistics of insignificant ones are colored in grey. Only genes with no more than 20 exons (19 introns) are shown. The reason for this is provided in the main text