Traces of polyploidy events in plant genomes. (a-f) The distribution of Ks values obtained from comparisons of sets of putative orthologous genome sequences between Br and the selected model plant species Os (a), Pt (b), Mt (c), and At (d), and from paralogous sequences in At (e) and Br (f) genomes. The vertical axes indicate the frequency of paired sequences, while the horizontal axes denote Ks values with an interval of 0.1. The black bars depict the positions of the modes of Ks distributions obtained from orthologous or paralogous gene pairs. At, A. thaliana; Br, B. rapa; Mt, Medicago truncatula; Os, O. sativa; Pt, Populus trichocarpa.