Figure 2. Ks distribution of GWD in selected monocotyledons and dicotyledons.

The density distribution of each monocotyledon (a) or dicotyledon (b) was calculated based on kernel density estimation with a bin size of 0.001. The evolutionary rate is relative slow in trees47,48, such as those of P. trichocarpa and V. vinifera. We suppose that the P. dactylifera genome also has this character similar to oil palm7. The minor peak of O. sativa (Ks ~0.06) was recently suggested to be a GWD event happened ~70 Mya and the genome underwent an illegitimate recombination followed by fast evolution49. Z. mays had a recent GWD event (Ks~0.2, ~5–12 Mya) as compared with other Gramineae species50. In M. truncatula, a peak near 0 (Ks~0.05) is due to local duplication and faster evolution rate as compared with other vascular plants51.