Refugial isolation and ecological niche differentiation promote genetic divergence of Oresitrophe and Mukdenia in Northeast Asia.

PREMISE

The demographic histories of temperate plants in Northeast Asia in response to Quaternary climate oscillations have long been the focus of evolutionary biologists, but have rarely been studied in herbaceous plants. Here, we investigated the phylogeographic patterns of Mukdenia and Oresitrophe.

METHODS

We sequenced two plastid regions for O. rupifraga (22 populations, 222 individuals), M. acanthifolia (five populations, 50 individuals), and M. rossii (14 populations, 139 individuals). To better understand the phylogeographic patterns of these species, we analyzed genetic diversity/structure, divergence times, demographic history, and distributional changes (with ecological niche modeling). We compared the inferred niche space of these species and addressed isolation by distance (IBD) and isolation by environment (IBE).

RESULTS

We confirmed the monophyly of each species and detected a phylogeographic division corresponding to an arid belt in North China. Oresitrophe rupifraga is inferred to have contracted into four refugia during Pleistocene interglacial periods. Mukdenia acanthifolia and M. rossii appear to have retreated to the Changbai Mountains and Korean Peninsula during that time. In contrast, a larger potential geographic distribution was inferred for each species during glacial periods. Significant ecological niche differentiation was detected among the three species, which may have been associated with their genetic divergence.

CONCLUSIONS

Refugial isolation, climatic barriers, and niche differentiation likely influenced the genetic divergence of Oresitrophe and Mukdenia. Our study has implications for the structure of plant diversity in temperate deciduous forests of Northeast Asia and provides insights into conservation units worthy of protection and management for species of both genera.