Phylogeography And Genetic Resources Of Eomecon Chionantha Hance, An Endemic Plant In Subtropical China

Eomecon chionantha Hance is a plant endemic to China and widely distributed inhumid evergreen broad-leaved forest area of eastern subtropical China. This species growsin humid habitats such as streamside, understory, which links its distribution to the historyof Pacific monsoon. To elucidate the relationship between the geographical distribution ofEomecon chionantha and the historical climate and particularly precipitation conditions, thisstudy sequenced two chloroplast DNA (rbcL-atpB and trnC-rpoB) fragments and nucleargene (ITS) from E. chionantha to investigate its phylogeographical and evolutionary history.A total of627individuals of E. chionantha Hance from37populations were collected. Threehundred and twenty individuals and302individuals were sequenced for chloroplast markerand ITS, respectively. The results revealed that E. chionantha Hance had22cpDNAhaplotypes and18nDNA types and showed a high genetic diversity （cpDNA HT=0.7398；nDNA HT=0.742）. The genetic differentiation of E. chionantha Hance was high for bothkinds of markers（cpDNA Gst=0.7348；nDNA Gst=0.7730）but had no obviousgeographical groupings. Demographic analyses of E. chionantha based on chloroplastsequences revealed that this species had experienced a population expansion during4730~14313years ago, which may caused by the intensified Pacific monsoon after the LastGlacial Maximum (LGM). The distrituion of chloroplast haplotypes and ITS types showedthat the expansion occurred mostly in western part of the distrituion range, whereas theeastern populations only expanded locally. This pattern is well consistent with thepalaeovegetation reconstructions that there was a non-forest area in the west part of E.chionantha during the LGM. Therefore, The expansion of E. chionantha may casued by theamelioration of climate conditions after the LGM, particularly by the increased precipitationthrough the strengthening of summer monsoon. Our results also showed that Eomeconchionantha Hance in the Quaternary glacial period had three refugia: Yunnan-guizhouplateau, Wuyi mountain and Luo Xiaoshan and Nine-ridge mountains.