Intron turnover frequencies and rates of (a) recurrent loss, (b) all loss and (c) single gain in five grass genomes.

<p>Branches of species tree represent evolutionary time. Frequency is defined as the number of events divided by the branch length and the unit branch length is million years (MY). Rate in a terminal node is measured by the number of events per intron per year. Rates are shown to the right of the vertical line and in the same line with the corresponding species codes. The 4-letter genome codes used are Zmay: <i>Zea mays</i>; Sbic: <i>Sorghum bicolor</i>; Sita: <i>Setaria italica</i>; Bdis: <i>Brachypodium distachyon</i>; Osat: <i>Oryza sativa</i>; Atha: <i>Arabidopsis thaliana</i>.