用nrDNA ITS序列探讨狭蕊龙胆属及其近缘属 (龙胆科)的系统发育

运用核糖体DNA内转录间隔区ITS序列对狭蕊龙胆属Metagentiana10种及其近缘属22种植物进行了系统发育分析。ITS分析结果表明狭蕊龙胆属是一个多系群:在系统发育树上,双蝴蝶属Tripterospermum和蔓龙胆属Crawfurdia的种类位于狭蕊龙胆属各分支中,而且双蝴蝶属和蔓龙胆属的种类也相互交叉;这一结果不支持将3个属各自独立为属。但是,在所有分析中,3个属共同形成一单系分支,是龙胆属Gentiana的姊妹群;这一结果与形态学、花部解剖学、细胞学、孢粉学和胚胎学等证据基本一致,狭蕊龙胆属应该从龙胆属中分离出来,它与双蝴蝶属和蔓龙胆属有更为密切的亲缘关系。根据分支图,在狭蕊龙胆属、双蝴蝶属和蔓龙胆属组成的复合群中,现已知的染色体基数x＝17、21和23可能存在网状和平行进化。

Phylogeny of Metagentiana and related genera (Gentianaceae) inferred from nuclear ribosomal ITS sequences

The infrageneric phylogeny of Metagentiana, a newly erected genus in the Gentianaceae, was constructed based on the analysis of the nucleotide sequences of the internal transcribed spacers (ITS) of nuclear ribosomal DNA of 10 representative species of this genus and 22 species of Gentiana, Tripterospermum and Crawfurdia. The analysis indicates that the genus Metagentiana is polyphyletic, because all sampled species of Tripterospermum and Crawfurdia are clearly embedded within Metagentiana. The species of Tripterospermum and Crawfurdia also did not cluster respectively as two monophyletic clades. These results do not merit status of three separate genera. However, these three genera clustered together as a monophyletic clade sister to Gentiana, which is in agreement with the previous conclusions on the separation of Metagentiana from Gentiana and its closer relationship to Tripterospermum and Crawfurdia based on studies of gross morphology, floral anatomy, chromosomes, palynology and embryology. The ITS sequences do not provide sufficient information to make a robust estimation of the phylogenetic relationships among dysploid cytotypes of x=17, 21 and 23, within the Metagentiana, Tripterospermum and Crawfurdia complex, but the preliminary results seem to indicate their reticulate and paralleling evolution.