Studies On The Phylogeny And Phylogeography Of Smilax China Complex Based On NrITS And CpDNA Sequence Variation

Smilax china complex, a member of sect. China in Smilax (Smilacaceae), includes a key species, S. china, and several relatives, S. china var. kuru, S. davidiana, S. trinervula, S. biflora, and S. nantoensis. Such species complex, whose distribution area covers the Sino-Japan floral region, distributes widely in East Asia, including the mainland of China, Taiwan, the Ryukyu, Korea and Japan. To investigate speciation and evolution caused by plant polyploidization, I studied on the phylogeny and phylogeography of Smilax china complex using nrlTS and two cpDNA regions, involving 358 individual from 37 populations of the complex. The main results are summarized as follows:(1) Select one to three individual from each population to reconstruct phylogeny tree of S. china complex based on nrlTS region. The result show that the Smilax china species complex forms a monophyletic group with strong support (bootstrap 72%, posterior probability) including S. china (2X,4X,6X), S. china var. kuru, S. davidiana, S. trinervula, and S. biflora, and S. nantoensis.(2) Population genetic and phylogeographic analysis based on cpDNA (matK, trnS-G) identify 25 different cpDNA haplotypes,17 populations (45.9%) have haplotype diversity. Central Japan and East China have the highest level of haplotype diversity. Phylogeny MP tree and TCS network based on cpDNA data suggest infer that S.china complex have diploid progenitor with ancestral haplotypes (H18, H19). Although this diploid progenitor has already been extinct, the ancestral haplotypes (H18, H19) are remained in potential refuges:the scJDB population in central Japan (h=0.5606,π×10﹣3=0.362,R=0.936) and the scCJX population in East China (h=0.6970,π×10﹣3=1.105,R=1.182). (3) Both phylogenetic reconstruction of nrITS and genealogical relationships of cpDNA sequences suggest the multiple origins of polyploid S. china. The polyploidization happened at least three times, which are located in South-west China, East China and Japan. Two major cpDNA lineages were identified in S. china complex, the Lineage A (Central-South-west-South China) and Grade B (East China-Korea-Japan). Demographic expansion could be detected in Lineage A (SSD=0.02099, P=0.055, Fu's Fs=-10.0181, P=0.006, Tajima'D=-1.83349, P=0.005,τ=1.25391), which might be a rapid expansion caused by polyploidization in around 0.094 Mya. Demographic expansion could not be detected in Grade B (SSD=0.50820, P=0, Fu's Fs=0.72222, P>0.05, Tajima'D=-0.65976, P>0.05).(4) The results suggest that Japan population migrated from refuge in Central Japan to South Japan. S. china diploid populations are remained in Taiwan, the Ryukyu and Yaku-shima in Japan, which reflect the genetic drift and allopatric speciation during expansion. Unique habitats on island led diversification between such diploid species, involving S. china var. kuru, S. nantoensis and S. biflora.