Fig. 1

Intron losses and gains during the evolution of nematodes. The present tree is the best one obtained in the maximum likelihood analysis of 1551 groups of orthologous protein alignments. The number of intron losses and gains of each branch was computed by the maximum likelihood with the rate-variation model of MALIN [65]. The values are displayed on the branch lines, using “+” and “−” symbols to represent intron gain and intron loss, respectively. The numbers behind species names are intron densities. Please see Additional file 1: Table S2 for the full name of each species and the values present in this figure. Sister figures (Additional file 2: Fig. S1 and S2) showing the ancestral intron densities and the rates of intron losses and gains are deposited in Additional file 2