Allopatric Lineage Divergence of the East Asian Endemic Herb Inferred from Low-Copy Nuclear and Plastid Markers.

The evolutionary histories of ornamental plants have been receiving only limited attention. We examined the origin and divergence processes of an East Asian endemic ornamental plant, . is an understory herb occurring in primary forests, which has been grouped into two varieties. We reconstructed the evolutionary and population demography history of to infer its divergence process. Nuclear and chloroplast DNA sequences were obtained from 21 populations on both sides of the East China Sea (ECS) to explore its genetic diversity, structure, and population differentiation. Interestingly, the reconstructed phylogeny indicated that the populations should be classified into three clades corresponding to geographical regions: the Japan (Honshu+Shikoku) clade, the Taiwan-Iriomote clade, and the Southeast China clade. Lineage divergence between the Japan clade and the Taiwan-Iriomote and Southeast China clades occured 1.14 MYA (95% HPD: 0.82-3.86), followed by divergence between the Taiwan-Iriomote and Southeast China clades approximately 0.75 MYA (95% HPD: 0.45-1.3). Furthermore, corolla traits (floral lobe length to tube length ratios) correlated with geographical distributions. Moreover, restricted gene flow was detected among clades. Lastly, the lack of potential dispersal routes across an exposed ECS seafloor during the last glacial maximum suggests that migration among the clades was unlikely. In summary, the extant exhibits a disjunct distribution pattern as a result of vicariance rather than long-distance dispersal. We propose that allopatric divergence has occurred in since the Pleistocene. Our findings highlight the critical influence of species' biological characteristics on shaping lineage diversification of East Asian relic herb species during climate oscillations since the Quaternary.