rDNA片段的序列分析在苦苣苔亚科系统学研究中的应用

THE APPLICATION OF SEQUENCE ANALYSIS OF rDNA FRAGMENT TO THE SYSTEMATIC STUDY OF THE SUBFAMILY CYRTANDROIDEAE(GESNERIACEAE)

本文测定了苦苣苔亚科４族、５属、５种植物的核糖体ＤＮＡ中的内转录间隔区（ＩＴＳ）序列及５．８ＳｒＲＮＡ基因的３′端序列。这几种苦苣苔亚科植物的ＩＴＳ１的长度范围为２３４～２５８ｂｐ，ＩＴＳ２的长度范围为２１８～２４６ｂｐ。Ｗｈｙｔｏｃｋｉａｂｉｊｉｅｎｓｉｓ的ＩＴＳ１（２５８ｂｐ）和ＩＴＳ２（２１８ｂｐ）在长度、序列及ＧＣ含量上均与其它几个种有较大差异，其代表的尖舌苣苔族可能很早就自苦苣苔亚科的祖先沿单独的一个分支演化。以Ｗ．ｂｉｊｉｅｎｓｉｓ作为功能性外类群，运用ＰＡＵＰ软件分析仅得到一个最简约树。在简约树上，Ｃｙｒｔａｎｄｒａｕｍｂｅｌｉｆｅｒａ、Ｂｒｉｇｇｓｉａｌｏｎｇｉｐｅｓ和Ａｎｎａｍｏｌｉｆｏｌｉａ形成一个单系群，ｂｏｏｔｓｔｒａｐ分析对该分支的支持强度达９７％，Ｃｈｉｒｉｔａｃｒａｓｉｆｏｌｉａ位于该分支的基部。由于系统树上Ｃｙｒｔａｎｄｒａｕｍｂｅｌｉｆｅｒａ代表的浆果苣苔族和Ａｎｎａｍｏｌｉｆｏｌｉａ代表的芒毛苣苔族均起源于长蒴苣苔族，结合这３个族在形态上存在过渡系列，建议将浆果苣苔族和芒毛苣苔族均并入长蒴苣苔族。

A molecular phylogeny of the subfamily Cyrtandroideae represented by five genera of four tribes was constructed using sequence analysis of the internal transcribed spacers (ITS) and partial 5.8 S rRNA gene (3′end) of nuclear ribosomal DNA. Direct PCR sequencing method was used in the study. The sequences of ITS 1 in the five species range from 234 bp to 258 bp in size and those of ITS 2 from 218 bp to 246 bp. The ITS 1 (258 bp) and ITS 2 (218 bp) of Whytockia bijieensis differ greatly from those of the other species in size, sequence and G+C content, and therefore the tribe Klugieae represented by W. bijieensis may have diverged from the ancestor of the subfamily Cyrtandroideae at a very early time. In PAUP analysis, W. bijieensis was used as the functional outgroup, and only one most parsimonious Fitch tree was obtained through exhaustive search. The tree has 353 steps, with CI=0.932 and RI=0.529. In the tree, Chirita crassifolia is basal to a monophyletic group comprising Cyrtandra umbellifera, Briggisia longipes and Anna mollifolia, and the monophyletic group is strongly supported by the bootstrap value (97). The tribes Trichosporeae and Cyrtandreae represented respectively by Anna mollifolia and Cyrtandra umbellifera both evolved from the tribe Didymorcarpeae, which can explain why many intermediate taxa exist among the three tribes. According to this, the present authors suggest that the tribe Trichosporeae and the tribe Cyrtandreae be merged with the tribe Didymocarpeae.