Research On Phylogenesis Of Sect. Camellia In The Genus Camellia

Sect. Camellia is the largest group with 57 recorded species in the Genus Camellia (Zhang HD 1998), of which 55 species were found in China and the other 2 species in Japan. The central distribution of the Sect. Camellia existed in China with plentiful camellia germplasm resources. Because species of the Sect. Camellia grows in many diverse environments, its exterior shapes, the species distribution and hybridization under its natural environment is extensive. Traditionally, Sect. Camellia has been known as an ornamental and a source of plant oil for centuries of cultivation in China. Variations under the artificial influence (including hybridization and polyploidization), the expansion and escape to wild environment, caused multiple diversity and complexity for morphology in interspecies (Zhang,1981). This leads to much debate in species classification, extending paths, differentiation and the evolutionary tendency in this section. Much research work has been done in the field of species classification by many scientists, but greater differences for classification systems existed in Zhang's system (1998) and Min's system.The systematic classification for this section, classification status for some species in this section, evolution process in interspecies were comprehensively studied on the base of research data from ITS method combined with traditional palynology and morphology regarding leaf abaxial epidermis, and major results are summarizes as below:1. Sect. Camellia is a natural grouping with close genetic relationshipThe common features are shown in the Sect. Camellia by the data from the above three methods, and indicate that Sect. Camellia is a natural group with close genetic relationship.2. Sect. Camellia is subdivided into 4 series from 2 subsectionsThe Sect. Camellia species are suggested to subdivide into 4 series from 2 subsections on the basis of data from ITS analysis jointly with palynology and morphology of leaf abaxial epidermis. The two subsections are named as subsection reticulate and subsection lucidissima Chang and the 4 series are named as Ser. Villosae Chang, Reticalatae Chang, Ser. Semiserrata and Ser. Pitardii.The results basically support Zhang's classification for this Section, but some new results are approached. These results show that there are very close relationship between morphology and nr DNA-ITS, palynology and leaf abaxial epidermis in this Section. And some certain relationship between relative relation and geographical distribution were found, which indicating that there are more close relative relationship in the same geographical region.3. There are two original centers and extending paths existed in the Sect. CamelliaIt is suggested that there are two extending paths for the original centers, evolution and distribution of Sect. Camellia, i.e. one original center located in Guangxi Region and Guangdong Province and toward to southwest and central south areas, and producing central Guizhou Province with adjacent areas. The diversity and continuous species are found in this original center. The other original center probably is located between Yunnan and Sichuan Province, toward to eastern area, and producing a distribution throughout Jiangxi, Zhejiang and Shandong Province. These results were basically familiar to Zhang's idea (1982) of eastern extension from the original center (Yunnan, Guangxi and Guangdong).4. Supporting the merging of C. chekiangoleosa and some species, and against merging of C. semiserrata and C. pitardiiIt is adequately supported that the four species such as C. liberistamin, C. crassissima, C. lucidissima and C. chekiangoleosa should be treated as one species of C. chekiangoleosa on the basis of data from the above three methods combined with morphology, which indicating this species has plentiful variation extent and scope. However, it is against the treatment of emerging C. semiserrata and C. pitardii as one species.5. The classification status of C. glabsipetala is remained to be further studied in the futureThere are largest genetic distances between the C. glabsipetala and species in the Subsection lucidissima Chang on the basis of data from ITS analysis, which showing further relative relationship among above mentioned species, but more close relationship with Sect. reticulatae. This species is much close to species from subject. lucidissima, compared with the species from subsection lucidissima based on the results from leaf abaxial epidermis. However, this species is close to species from Subsect lucidissima on the basis of pollen morphology. Thus, classification of this species is remained to be further studied in the future.