Figure 1. A map showing the species' ranges and a scenario of possible hybridization between species.

Letters A–D indicate the sampling sites for M. simplicifolia (star) and M. betonicifolia (filled circle), A: Cuona, B: Linzhi, C: Milin, and D: Laojunshan Mountain. Triangle, solid circle, and pentagram represent some sampled populations of M. integrifolia, M. betonicifolia, and M. simplicifolia, respectively. Putative hybrid populations are indicated by the overlapping of solid circle and triangle.