Fig. 4.

Evolution of intron size. Neighbour joining tree derived from exon alignments with the y-position of nodes determined by changes in intron size inferred by Sankoff maximum parsimony. Positions along the x-axis indicate cumulative Kimura two-factor distance from ancestors, positions along the y-axis indicate cumulative changes in mean (10×log₂) intron size from ancestors. Colours of lines indicate taxonomic clade membership of leaf and inferred ancestral nodes. Intron sizes in teleosts (red) and aves (cyan) appear to have decreased dramatically from their respective ancestral states