基于染色体计数和ITS序列初步探讨横断山区柴胡属植物(伞形科)的系统发育

横断山区是中国柴胡属Bupleurum植物的分布中心。本文对横断山区6个种2变种进行了染色体记数报道,其中4个种2变种是首次报道。对横断山区的10个种4个变种、中国北方（河北和黑龙江）的3个种的nrDNA ITS进行测序,同时从GenBank里面下载同属的来自非洲和地中海西部的16个nrDNA ITS序列数据,结合染色体数目变化结果,初步探讨了横断山区柴胡属植物的系统发育。结果表明横断山区可能是现代柴胡属植物的频度中心和多样分布中心之一。它们的祖先种可能是非洲北部的木本柴胡属植物B.fruticosum,或者是地中海西部的柴胡属植物,推测是通过中东和高加索扩散而形成的,其中与非洲南部特有种B.mundtii的亲缘关系也较近;染色体基数演化趋势是：8是较原始基数,6和7是次生基数,其染色体异基数变异和多倍化可能是物种形成、进化以及向外扩散的主要方式;在ITS系统发育树中,中国柴胡属植物染色体基数为8的种类聚为一支,染色体基数为6和7的种类聚为了一支,不支持舒璞等（1998）关于中国柴胡属的属下分类系统。结合已有的形态学、细胞学、孢粉学证据和ITS系统发育树,建议窄竹叶柴胡B.marginatum var.stenophyllum独立成种。

Phylogenetic inference of the genus Bupleurum(Apiaceae)in Hengduan Mountains based on chromosome counts and nuclear ribosomal DNA ITS sequences

Hengduan Mountains are the diversity center for the genus Bupleurum of Apiaceae in China.This Paper reports chromosome numbers of six species and two varieties of Bupleurum,and for four species and two varieties their chromosome numbers are reported for the first time.The phylogeny of Bupleurum was investigated based on the ITS region of the nuclear ribosomal DNA(nrDNA)of 14 taxa from the Hengduan Mountains,3 taxa from the North China(Hebei and Heilongjiang),and 16 taxa from Africa and the Mediterranean region.Variations in chromosome numbers and the ITS sequences were used to infer Phylogenetic relationships between Bupleurum species in Hengduan Mountains.The results showed that the Hengduan Mountains might represent one of the frequency and diversity centers for Bupleurum.The ancestors of Bupleurum species in the Hengduan Mountains may be related to the woody B.fruticosum in North Africa,or the species in the western Mediterranean region.It is postulated that the ancestral population migrated into Hengduan Mountains through the Middle East and the Caucasus.Furthermore,the neo-endemic B.mundtii in South Africa appeared to be a close relative of the species in the Hengduan Mountains.In the trend of basic chromosome number evolution,x=8 should be regarded as the ancestral basic number,while x=6.7 as the derived ones.The Bupleurum species in the Hengduan Mountains have been undergoing changes in the basic chromosome numbers or the ploidy level.The ITS phylogenetic tree showed that the Chinese species were divided into two clades:one with the basic chromosome number x=8,and the other with x=6,7.The results rejected the previous infrageneric classification of Bupleurum in China.We further suggested to raise B.marginatum Var.stenophyllum to species rank based on the combined evidence from morphology,karyology,pollen morphology,and the ITS phylogenetic tree.