单种属弥勒苣苔属系统位置研究:基于分子和细胞学数据(英文)

The Systematic Placement of the Monotypic Genus Paraisometrum(Gesneriaceae) Based on Molecular and Cytological Data

弥勒苣苔属是苦苣苔科的单种属,仅分布于中国西南部。为探讨弥勒苣苔在苦苣苔亚科中的系统位置,我们选择了苦苣苔亚科116个类群,外类群为苦苣苔亚科以外的7个物种。用最大简约法(MP)和贝叶斯分析(BI),对以上类群的核基因ITS以及两个叶绿体基因trnL-F、atpB-rbcL数据进行了独立和联合分析。在三个片段联合分析的结果中,弥勒苣苔与马铃苣苔属、后蕊苣苔属、金盏苣苔属、直瓣苣苔属以及川鄂粗筒苣苔构成一个强烈支持的分枝。MP树中,此分枝为并系,而在BI分析中,弥勒苣苔与川鄂粗筒苣苔、直瓣苣苔属互为姐妹类群。同时,第一次报道了弥勒苣苔的染色体数目(2n=34)。根据前人报道,马铃苣苔属、后蕊苣苔属、粗筒苣苔属和直瓣苣苔属的染色体数目同为2n=34,这进一步支持我们的分子系统发育分析。

Paraisometrum, is a monotypic genus endemic to Southwest China, with an uncertain systematic position. To resolve the phylogenetic relationships of Paraisometrum within subfamily Cyrtandroideae, we performed phylogenetic analyses of 116 taxa placed in the subfamily Cyrtandroideae and 7 outgroup species selected from other Gesneriaceae subfamilies. The independent and combined analyses were performed on three DNA datasets： the nuclear internal transcribed spacer regions （ ITS ） and two chloroplast regions （ trnL-F, atpB-rbcL ）. Maximum Parsimony （MP） and Bayesian Inference （BI） were used for tree construction. The combined three gene dataset strongly support Paraisometrum in a clade containing Oreocharls, Opithandra, Isometrum, Ancylostemon, and Briggsla rosthomii. In the MP tree this lineage is an unresolved polytomy, but BI resolves Paraisometrum as sister to B. rosthomii and the Ancylostemon clade. We did the first chromosome counts of Paraisometrum （2n = 34）. The diploid number 34 has also been reported for Oreocharis, Opithandra, Briggsia and Ancylostemon, which lends further support to the placement of Paraisometrum in this lineage.