Comparison of the relative positions between lost introns and conserved intronsa.

aThe relative position was defined as intron position divided by the length of the coding sequence from the 5′ end. For introns lost at the ancestor nodes, the relative position was calculated in each of the species. Species name abbreviations: S. cryophilus (Scry), S. octosporus (Soct), S. pombe (Spom).bAll the relative intron positions were grouped by lost introns and conserved introns and a Mann-Whitney U test was used to calculate the P values.cFor each intron-lost gene, the median positions of lost introns and conserved introns were paired and a Wilcoxon signed rank test was used to calculate the P values. Intron-lost genes with no conserved introns were not counted; therefore, the sample sizes were smaller than grouped comparisons.