Fig. 1

Species trees. a Evolutionary relationships among 19 plant species used in this study. All bootstrap values that are not shown in the graph are maximal (100). Red stars represent whole-genome duplication events and purple stars represent whole-genome triplication events. These events represent those already known at the start of this study with their proposed phylogenetic positions as described in the literature. b Zoom-in to the Lamiales clade. Numbers in a circle on top of internal nodes represent the node names as referred to in the text, and numbers below each branch are duplication frequencies calculated for each phylome. Each phylome and their corresponding duplication frequencies is colored differently: O. europaea is green, F. excelsior is light blue, U. gibba is brown, S. indicum is red, M. guttatus is orange, and S. miltiorrhiza is yellow