Phylogenetic Studies Of Smilax China Complex And Sect. Nemexia In Smilax (Smilacaceae)

Phlogenetic reconstruction of the Smilax china complex (Smilacaceae) and the species of Smilax sect. Nemexia (Smilacaceae) is presented based on the analysis of morphological analysis, random amplified polymorphic DNA (RAPD), allozyme and sequence data from the nrDNA ITS region and four fragments of cpDNA including matK gene, trnT-L, trnL-F and rp116 intergenic spacers. In combination with the previous morphological and karyological data, conclusions were made as the followings:1. Phlogenetic reconstruction of the Smilax china complex (Smilacaceae)1.1 Morphological analysisA clatistic analysis of 60 samples of S. china complex was carried out based on nine morphological characters.The result showed that some variations were found among the different taxon, but they are overlapped due to high varibal morphologies.1.2 Genetic differentiation based on RAPD analysisRAPD analysis was conducted on 21 groups. Out of 36 RAPD primers, 15 generated highly reproducible and stable DNA fragments. Using these primers, 275 discernible DNA fragments were produced, among which 246 (PPB=89.47%) were polymorphic, which indicated high levels of genetic variation. A UPGMA dendrogram was constructed based on the genetic distance and showed three clusters, namely A, B and C. Cluster A included 8 outgroups, cluster B included all species of the complex except S. china in GX population, and cluster C included S. ferox and S. china in GX population. The results indicated that S. china is a stable species and little differentiation was found between S. china and its related species in the complex.1. 3 Phylogenetic analysis based on the sequence of nrDNA ITS, cpDNA matK and trnT-LSequence data of nrDNA ITS region and two fragments of cpDNA including matK gene and trnT-L intergenic spacer strongly supported the monophly of S. china complex (different populations of 5. china, S. davidiana, S. trinervula, S. polycolea, S. lebrunii, and S. biflora). Diploid population of S. china in Hubei, S. davidiana and S. trinervula formed a clade, which was closely related to the main clade composed of the major polyploidy complex. This indicated the diploid populations were possibly the ancestors of S. china complex. The populations in Mt. Lao and Korea formed a unique clade, which indicated the common origination of the two populations. Another clade comprised of 4X JF population, S. lebrunii and S. polycolea, showing the divergence or the different derivation from the main clade. As revealed in the aligned ITS sequences, the same sequence type was found in JF population, S. polycolea and S. lebrunii due to more than 20 different loci from others. GX population formed a unique clade and high frequency of fragment indels were found. Additionally, S. davidiana was supposed to be one of the ancestors of S. china complex because it was clustered with HB population.1. 4 Allozyme analysisVariation in allozyme patterns of 8 enzyme systems with 25 alleles in 11 populations of S. china and 3 affinitive species were investigated. The result supported that diploid populations of S. china complex, S. davidiana and S. trinervula were ancestor species of 4X and 6X species, and the S. china complex populations of GL and GZ are allotetraploid. Suggestions can also be made that S. china arose from multiple origins and it is an old, but being active differentiation group.In combination with the morphological, karyological and molecular data, inference can be made: 1) S. china complex is a monophly, including the key species of S. china, and other species of S. davidiana, S. trinervula, S. biflora, tetraploids S. polycolea and hexaploids S. ferox, S. lebrunii. 2) The diploid populations of S. china complex and diploid species of S. davidiana, S. trinervula and S. biflora are the ancestors of the polyploidy complex. 3) From the distribution of tetraploid and hexaploid populations of S. china and the gene tree, suggestions were given that before Taiwan, Ryukyus and Japan were seperated from Asia continent in the middle of Pleistocene, the tetraploid populations of S. china had distributed widely, however, the hexaploids populations derived lately from hybridization. 4) The tetraploid Jinfo population and S. polycolea, S. ferox and S. lebrunii may have other diploid ancestors. 5) Origination center of the complex is hypothesized to be the zone from central to southwestern China and the polyploidy has originated from the hybridyzation and reduplication of non-miosis gametes in multi places and populations. 6) The size of the fruits are not supposed to be stable genetic character.2. Phylogeny reconstruction of Smilax sect. NemexiaPhylogeny tree based on three molecular markers supported that the species of Smilax sect. Nemexia is a stable monophly and the geographical distribution has played an important role in the differentiation of this group, but not morphological character. Smilax sect. Nemexia exhibits an East Asian-North American phytogeographic disjunction. The common ancestor of the group is assumed to have originated in Asia and spread northeastward to North America through the Bering Land Bridge. Catastrophic geological activities of Pleistocene glaciation obstructed the geneflow between Asia and North-America, and fragmentated the continuous distribution of the group in North America into eastern and western parts of North-America. As revealed by the phylogeny tree, the North American species form a clade, with S. jamesii, the only species from western North America, as sister to the "5. herbacea complex" from eastern North America.