Phylogeny Of The Genus Cycas (Cycadaceae) In China

Chinese Cycad resource is rich and with four groups of six groups in the world, whose diversity and richness is rare among the world. However, Chinese Cycad is widespread of phenomenon, with less morphological classification and small number of observing samples as well as unknown original place for some new species, which cause big controversy on classification. The purpose of this study was to discuss the Chinese Cycas phylogenetic relationships by using the methods of molecular systematics, in order to provide molecular evidence for its taxonomic revision.To build the Chinese Cycas Phylogenetic relationships of 32 representative species, Maximum parsimony, Maximum likelihood and Bayesian inference were using in the study of 7 nuclear gene (Cos26、CyAG、GroES、GTP、HTS、ITS、PhyP) and 1 chloroplast DNA (matK). Major feature of this study was that all materials used were almost from type specimen、type of living plant or type locality. The main reuslts of this study are as follows:1. Determined the system relationship between the main groups of Chinese Cycas. All three methods showed similar topology, which divided the Chinese Cycas into three clades. The first clade was Section Indosinenses which was forming a sister relationship with the rest of the groups. The second clade consisted of two sections, Sect Asiorientales and Sect Panzhihuaensis, which were strongly suppoerted that Sect Asiorientales was a sister relationship to Sect Panzhihuaensis. The third clade was Sect Stangerioides, which were strongly suppoerted that Sect Stangerioides was also a sister relationship to Sect Asiorientales + Sect Panzhihuaensis.2. Probed the species relationship between the main groups of Chinese Cycas. All three analysis methods indicated that Sect Indosinenses consisted of two species, C. hongheensis and C. pectinata. Compared with C. hongheensis, the high bootstrap demonstrated that C. pectinata was closely related to C. siamensis which is distributed in Southeast Asia. Sect Asiorientales also consisted of two species, C. revoluta and C. taitungensis, which the high bootstrap demonstrated that C. revoluta was quite close related to C. taitungensis. Within the Sect Stangerioides, the three analysis methods provided a poor phylogenetic resolution so only some lineages resolved. It is noteworthy theat the C. longlinensis was highly supported to be merged into C. guizhouensis which indicated that the two species should be combined together. Since C. multifrondis was supported to be merged into C. multipinnata which indicated that C. multifrondis should be wild hybrids of the C. multipinnata. C. parvulus was supported to be merged into C. diannanensis which indicated that the two species should be combined together. C. shiwandashanica was supported to be merged into C. blalansae which indicated that the two species should be combined together. C. gracilis was supported to be merged into C. debaoensis which indicated that the C. gracilis was C. debaoensis.3. Identified the unknown ancient cycad from Dayi Farm of Yulin, Guangxi. The unknown ancient cycad which came from the farm in Yulin Guangxi province was forming a monophyletic with C. szechuanensis which was from Sichuan, which came out the result the indicated that the unknown ancient cycad should be the C. Szechuanensis.