Phylogeography Of Three Forest Plants In Subtropical China

Subtropical China is a major biodiversity hotspots in the world. Phylogeographic patterns of plant species in the region have been a topic of concern among evolutionary botanists. In this study, we investigated the effects of climatic changes and tectonic events on phylogeographic structure of plants in subtropical China by applying various molecular markers. The main results were as follows:The time to the most recent common ancestor of all 17 chloroplast haplotypes in Cyclocarya paliurus was 16.69 Ma(95% HPD 8.42–27.86 Ma), which largely coincides with the initial intensification of the Asian monsoon and global climate cooling during the Early to Middle Miocene. Chloroplast lineage diversification started to increase in the early Late Miocene, with peaks at c. 9.6 Ma and c. 3.6 Ma, corresponding temporally to two subsequent intensification events of the Asian monsoon. Bayesian skyline plots of both markers revealed that C. paliurus could have experienced at least two waves of expansion since the middle Pleistocene. The distributions of chlorotypes and clades were both consistent with a multiple-refugia model but with strong signals of range expansion.Sequence variation of two chloroplast intergenic spacers(IGSs) in 369 individuals from 54 populations of Sargentodoxa cuneata was examined. All chloroplast haplotypes clustered into two lineages(A and B) in a Bayesian tree, and most haplotypes(18 out of 26)originated during the mid-Pleistocene(0.63–1.07 Ma). Demographic analyses detected a recent range expansion that occurred at 95.98 ka(CI: 61.7–112.53 ka) for Lineage A. The genetic signature of an ancient range expansion after the Middle Pleistocene Transition(MPT) was also evident. Three recolonization routes were identified in subtropical China.The results suggest that temperate plants in subtropical China may conform to the EC model to some extent. However, the genetic signature from multiple historical processes may complicate the phylogeographic patterns of organisms in the region due to the mild Pleistocene climate. This study provides a new perspective for understanding the evolutionary history of temperate plants in subtropical China.The results of cpDNA, nuclear ITS and SSRs showed that Eomecon chionantha has no obvious phylogeographic structure. Annual precipitation has not fluctuated greatly in Wuyi Mountains, Luoxiao Mountains, Nanling Mountains and the eastern Yungui Plateau duringthe Pleistocene, where E. Chionantha survived during the glacial periods. These results suggest that the populations of E. Chionantha could have not separated in those region throughout the Pleistocene, resulting in limited population differentiation. Western regions(western of Yungui Plateau, Wuling Mountains and Daba Mountain) could be more drier than southeast part of the distribution range during the glacial periods of Pleistocene.However, the precipitation increased since Holocene Megathermal, making the refugial populations in west Nanling Mountains migrate to Yungui Plateau and Daba mountain.