应用ITS区序列对秋海棠属无翅组分类学问题的探讨

以侧膜组（Sect.Coeloecentrum)的Begonia cirrosa和单裂组（Sect.Reichenheimia)的B.henryi为外类群，对秋海棠属（Begonia L.)无翅组（Sect.Sphenanthera)9种2变种及秋海棠组（Sect.Begonia)4种进行了ITS区（包括5.8s rDNA)序列的测定。发现该属的ITS序列较一般类群要长一些，所测的序列长度变化范围为648－743bp。这些序列经Clustal X软件排序后序列总长为756个位点，gap做缺失处理时，变异位点和信息位点分别占26.41%和10.11%。运用PAUP4.0b8软件分析，获得6棵最大简约树，步长为286，一致性指数（CI）和维持性指数（RI）分别为0.8287和0.7841，利用6棵最简约树获取严格一致树，并作Bootstrap检测。结果表明：1.支持将原无翅组内子房3室的种类移入秋海棠组，而将子房4室的种保留，成立四室组（Sect.Sphenanthera)；2.将B.tetragona作为B.acetosella的异名处理得到一定的支持；3.B.crassirostris的系统位置有待进一步的研究。

Studies on the Classification of Begonia Sect.Sphenanthera Based on Nuclear Ribosomal DNA ITS Sequence Data

The sequences of nrDNA internal transcribed spacers (ITS) (including 5 8S rDNA) of 9 species and 2 varieties in Sect. Sphenanthera ,4 species in Sect. Begonia were examined and analyzed B cirrosa (sect. Coelocentrum ), B henryi (Sect. Reichenheimia ) as outgroup. The length of these sequences is 648-743bp,and the aligned length of ITS region is 756 position, which provides 26 41% variable sites and 10 11% phylogenetical informative sites when gaps are treated as missing. Six most parsimonious trees, with length of 286, consistency index ( CI ) of 0.8287 and retention index ( RI ) of 0 7841 were obtained by PAUP 4 0b8 analysis. The topology of the strict consensus tree shows that: 1. transferring the species with 3 locular ovaries from Sect. Sphenanthera to Sect. Begonia was supported; and the remaining species with 4 locular ovaries should be kept in Sect. Sphenanthera ; 2. B tetragona should be synonymized with B acetosella ; 3. the phylogenetic position of B crassirostris has not been resolved in this study and needs to be further studied.