铁破锣属的系统位置——ITS(nrDNA)序列证据

THE SYSTEMATIC POSITION OF BEESIA: EVIDENCE FROM ITS(nrDNA) SEQUENCE ANALYSIS

对Ｂｅｓｉａｃａｌｔｈｉｆｏｌｉａ等５种金莲花亚科植物的核糖体ＤＮＡ中的内转录间隔区（ＩＴＳ）序列及５８ＳｒＲＮＡ基因的３′端序列进行了测定。这几种金莲花亚科植物的ＩＴＳ１的长度范围为２２５～２３２ｂｐ，ＩＴＳ２的长度范围为２０１～２１７ｂｐ。Ｂ．ｃａｌｔｈｉｆｏｌｉａ的ＩＴＳ１（２２７ｂｐ）和ＩＴＳ２（２１５ｂｐ）的长度及序列均与升麻属及类叶升麻属植物相近，其５８ＳｒＲＮＡ基因的３′端序列也近乎与升麻属及类叶升麻属植物完全一致（仅一个碱基缺失的差异），但其在上述几方面均与金莲花属植物相差甚远。以Ｒａｎｕｎｃｕｌｕｓｅｎｙｓｉ作为外类群，运用ＰＡＵＰ软件进行的系统发育分析表明：Ｂ．ｃａｌｔｈｉｆｏｌｉａ，Ｃｉｍｉｃｉｆｕｇａａｃｅｒｉｎａ，Ｃ．ｂｒａｃｈｙｃａｒｐａ和Ａｃｔａｅａａｓｉａｔｉｃａ形成一个单系群，并得到ｂｏｏｔｓｔｒａｐ分析的极强支持，Ｂ．ｃａｌｔｈｉｆｏｌｉａ位于这一单系群的基部。这一ＤＮＡ序列分析结果与来自植物化学、孢粉学和细胞学的研究结果相吻合，更进一步支持铁破锣属是升麻族的自然成员，并可能是升麻族中一个最原始的类群。

Discussed in the present paper is the systematic position of Beesia, a small ranunculaceous genus mainly distributed in SW China. Sequences of the internal transcribed spacers (ITS) and 3′ end of 5 8 S rRNA gene of Beesia calthifolia, Trollius chinensis, Cimicifuga acerina, C. brachycarpa and Actaea asiatica were determined by direct PCR sequencing method. The sequences of ITS 1 in the five species range from 225 bp to 232 bp in size and those of ITS 2 from 201 bp to 217 bp. Beesia is very similar to Cimicifuga and Actaea not only in size, sequence and G+C content of ITS, but also in sequence of 3′ end of 5 8 S rRNA gene. In PAUP analysis, Ranunculus enysii was used as outgroup, and the most parsimonious tree was obtained through exhaustive search. The gaps were treated respectively as missing characters and the fifth base in two analyses.The two analyses show that a monophyletic group comprising Beesia calthifolia, Cimicifuga acerina, C. brachycarpa and Actaea asiatica is strongly supported by the bootstrap value. In the monophyletic group, Beesia calthifolia is basal to the other three species. The present DNA sequence analysis demonstrates that the genus Beesia should be placed in the tribe Cimicifugeae, which is consistent with the results from phytochemistry, palynology and cytology. In addition, Beesia may be the most original genus in the tribe Cimicifugeae in view of simple leaf, apetalous flower and molecular evidence.