A Floristic Study On The Wild Seed Plant Of Xichou County

The floristic copositions,characteristics,endemism,origin and evolution in Xichou county were studied on the bases of field investigation,literatures cheked,specimens collected and identified.The main results are as follows.1.There are 2060 species(including varieties and subspecies),belonging to 771 genera in 184 families,recorded in Xichou county.Among them,12 species of gymnosperms belong to 8 genera in 6 families,2048 species of angiosperms belong to 763 genera in 178 families.In these angiosperms,including 283 species of monocotyledons in 136 genera of 25 families,and 1765 species of dicotyledons in 627 genera of 153 families.2.The dominant families and genera are obvious,including many monotypic family and monotypic genera.36 dominant-families(20.11%)were recorded,including 1311 species(63.64%)of 481 genera(62.39%).200 dominant-genera were recorded,the cumulative contribution rate up to 60%.Furthermore,29 monotypic families and 3 monotypic families in the world were recorded.3.The geographic distribution types are diversified and the origin is complex of wild seed plants in Xichou county.184 families were divided into 8 distribution types and 10 variants,no Chinese endemic families;771 genera were divided into 13 distribution types and 18 variants,and no the distribution of Central Asia;2060 species were divided into 15 distribution types and 10 variants.4.The flora in region is mainly the tropical,but also contains some temperate types in the level of family,genera,and species,the tropic character decreased as the level of family,genera,and species.97 tropical families,489 tropical genera and 1181 tropical species distributed in this region,occupying 70.29%,66.85% and 57.89% of total of the non-world types.Likewise,41 temperate families,239 temperate genera and 859 temperate species distributed,occupying 29.71%,33.15% and 42.11% of total of the non-world types.5.The endemism of the flora in Xichou is rather remarkable,strong species differentiation,both old and new.There are 12 Chinese endemic genera.645 Chinese endemic species,of which 182 are Yunnan endemic and 40 are Xichou county endemic.6.The floristic comparison with the 12 limestone area,it can be concluded that the flora of Xichou county is the closest to the Laohutiao Nature Reserve in Guanxi;Nanxi river in Yunnan.However,is the most distant Huangdangyu Nature Reserve in Anhui,Laoshan in Nanjing,Guishan in Shilin of Yunnan and Yuntai mountain in Guizhou.7.Among the floristic composition of the species,tropical Asia and its variants were dominant,accounting for 51.56% of all species,especially 190 species from Vietnam(or the Indo-China Peninsula)to south or southwest China,accounting for 9.22% of all species in the region.