Polyploidy events in the evolution of the Brassica genome. Each star indicates a WGD (1R, 2R, and 3R) or WDT (4R) event on the branch. Estimation of dates for polyploidy and speciation events are given in million years and are based on the Ks analysis performed in this study, except for the 1R event, which was inferred from a previous report . A geographic time-table is provided on the right border of the figure. At, A. thaliana; Bna, B. napus; Bo, B. oleracea; Br, B. rapa; Mt, Medicago truncatula; Os, O. sativa; Pt, Populus trichocarpa.