Fig. 3

Conservation of intron sizes across the vertebrates. A, Mutual information between intron size for all pairs of species having less than 2.5% of introns shorter than 2⁵ bp. Species are arranged by taxonomic order obtained from a neigbhour-joining tree based on exon alignments (Fig. S6). High mutual information is seen within taxonomic groupings, but is much lower for teleosts than mammals and the Sauria. B, Kimura-two factor distances (x-axis, based on exon alignments) plotted against mutual information (y-axis) for all within clade species pairs. Mutual information is generally lower within the teleosts than mammals for equalivent exon derived distances indicating a higher rate of change in intron size within the teleosts