Phylogenetic And Phylogeographic Study Of S.sieboldii Group

Smilax hispida group (Smilacaceae, Liliales) are climbing vines, with herbaceous, heart-shaped leaves, and prominent blackish needlelike prickles on the stem. There are six species in this group showing an Eastern Asia-North America disjuct distribution. Two of the species (S. scobinicaulis C.H. Wright and S. sieboldii Miq.) are found in eastern Asia (referred to S. sieboldii comlex in this research), widely distributed in southern-temperate and subtropical deciduous forests of China, Korea and Japan at an altitude range of1000-2000m and100-1000m respectively. Morphology similarity and parapatric distribution makes it difficult to identify these two species.The present study generated DNA sequence data from two nuclear DNA (ITS and at103) and five chloroplast DNA (trnL-trnF, ycf6-trnC, rpl16, rbcL, matk) regions to address the species boundary of the complex. Sequence data from three regions of them (ITS、trnL-trnF、ycf6-trnC) were used to address the phylogeographic pattern of the species complex. Species boundary and population genetic diversity were assessed using phylogenetic analysis and GSI, as well as morphology. Demographic simulation in glacial-interglacial period was carried out in combination with the morphology, paleogeology, paleoclimatology and ecological nichle modeling to estimate the interspecies gene flow and glacial-interglacial distribution of the complex. The main conclusions are listed blow.1) Phylogenetic analysis of S. sieboldii Group in Eastern AsiaPhylograms were obtained from maximum parsimony, maximum likelihood and Bayesian analysis of combined data set (ITS/at103/trnL-trnF/ycf6-trnC/rpl16/rbcL/matk) of S. sieboldii group. S. sieboldii comlex was showed to be monophyletic and sister to the North-American species in&hispida group, and was located in the New World clade in the phylogenetic tree of Smilacaceae. Despite the parapatric distribution and high morphologic similarity, speciation appears to have completed in this comlex and the geographic boundary of these two species lies in the eastern-Taihang Mountain, Dabie Mountain and eastern-Mufu Mountain. According to the morphological statistics, the peduncle of S. sieboldii is equal to or longer than the petiole while in S. scobinicaulis the peduncle is only half of the petiole length. The time of the Asian S. hispida lineage dispersed into East-Asia was estimated to the late Miocene (ca.11.07mya) based on results from BEAST analysis. The lineage then quickly diversified via allopatric speciation and subsequently evolved independently.2) Population Genetic Diversity Analysis of S. sieboldii GroupPopulation genetic diversity was evaluated using ITS and2cpDNA sequnces (trnL-trnF/ycf6-trnC). The results showed high genetic diversity within S. sieboldii group (h=0.899; π=2.35×10"3). Most variation was observed between the two species while the rest mainly existed between different groups identified by AMOVA analysis. One reasonable explanation for this phenomemon was that the genetic drift have contributed to the low genetic diversity within population and genetic isolation between populations following the founder effect during the dispersal of S. sieboldii group.3)Phylogeographic pattern of S. sieboldii group Three lineages (the North lineage, the Southwest lineage, and the Southeast lineage) were identified in S. scobinicaulis populations according to haplo-/generaltype network analysis and SAMOVA analysis. With the simulation of ecological nichle modeling (ENM), the uplift of Qinghai-Tibet Plateau (QTP) and the existence of abundant mountains and deep valleys were the main cause of the lineage formation within S. scobinicaulis after speciation (ca.4.77mya). High haplo-/generaltype diversity was observed within HBSN population which located in Shennongjia area and prossessed4cpDNA haplotypes and3ITS generaltypes. With the possession of derived haplo-/generaltype from different lineages, HBSN population was less likely to be the refuge of S. scobinicaulis rather than the result of expasion and secondary contact of different lineages.Network analysis of S. sieboldii has revealed high haplo-/generaltype diversity and glacial refuge of S. sieboldii, with two ancestral haplo-/generaltype (H1and G1) and two unique haplotype (H19and H20). Based on SAMOVA analysis, there were three lineages within S. sieboldii (the Southeast China lineage, the Japan lineage, the Northeast China-Korea lineage). Sea level fluctuations throughout the inter-/postglacial cycles had lead to the fragmentation of S. sieboldii populations, during mid Pliocene (ca.3.32mya). According to ENM, S. sieboldii had retreated to southeast part of China and a very small region south of Japan during Last Glacial Maxium (LGM), and then recolonized to Japan, Korea and northeast of China. Temperate gene flow may exist between Korea and southern Japan during LGM, with the exsistence of1bp-differed generaltype G14and G17. 4) Gene flow between S. scobinicaulis and S. sieboldiiThe random distribution of haplotype H7within Northern lineage of S. scobinicaulis suggested ancient geneflow between two species or the presence of ncestral polymorphism in S. scobinicaulis. Hybridization of the two species likely have occurred in Mt. Dabie region. One individual of S. sieboldii (AHTT2) collected in this region may have hybridized with S. scobinicaulis of generaltype G1and G11and has the haplotype of H2which is the ancestral haplotype of S. scobinicaulis.