用叶绿体rbcL和rps4-trnS区序列确定亚洲特有单型属——篦齿蕨属的系统位置

Phylogenetic position of the monotypic genus Metapolypo-dium Ching endemic to Asia: evidence from chloroplast DNA sequences of rbcL gene and rps4-trnS region

篦齿蕨属MetapolypodiumChing是亚洲大陆特有植物,仅含篦齿蕨Metapolypodiummanmeiense(Christ)Ching1种,分布于中国西南及其邻近地区,其系统位置一直是一个有待解决的问题。本文用叶绿体rbcL和rps4-trnS区序列探讨篦齿蕨属的系统位置。我们对篦齿蕨及其近缘类群的叶绿体rbcL和rps4-trnS区进行PCR扩增和序列测定。用最大简约法、邻接法和贝叶斯推断法对自测序列结合由GenBank下载的rbcL和rps4-trnS区序列进行独立和联合的系统发育分析,所构建的系统发生树的拓扑结构基本一致。结果显示:篦齿蕨属与多足蕨属PolypodiumL.emend.Ching的关系较疏远,而与水龙骨属PolypodiodesChing和拟水龙骨属PolypodiastrumChing的成员聚成一个支系,与栗柄水龙骨Polypodiodesmicrorhizoma(C.B.ClarkeexBaker)Ching的关系最近。根据本文的研究结果,我们赞成秦仁昌1978年的分类系统,即分别承认多足蕨属、篦齿蕨属、水龙骨属、拟水龙骨属和棱脉蕨属SchellolepisJ.Sm.为独立的类群。根据分子系统学证据,宜将栗柄水龙骨转移到篦齿蕨属中。

Metapolypodium Ching, a monotypic genus endemic to Asia mainland （SW China and its neighboring regions）, is still in dispute as to its systematic position. In this paper, the phylogenetic relationships of this genus was examined based on the chloroplast DNA sequences of rbcL gene and rps4-trnS region. The rbcL genes and rps4-trnS region of M. manmeiense （Christ） Ching and its closely related species were sequenced. The combined relative sequences downloaded from the GenBank, consisting of three data sets-rbcL genes, rps4-trnS region including rps4 and rps4-trnS intergenetic spacer, and the combined matrix-were used to assess relationships among them with the neighbor-joining （NJ）, maximum-parsimony （MP） and Bayesian inference （BI） analyses. The phylogenetic trees based on individual sequence data and the combined data are topologically similar and reveal that M. manmeiense forms a clade with the members of Polypodiodes and Polypodiastrum, which is not related to any member of Polypodium. The trees also strongly support the close relationship between M. manmeiense and Polypodiodes microrhizoma （C. B. Clarke ex Baker） Ching. We should agree with Ching＇s opinion, recognizing Polypodium L. emend. Ching, Metapolypodium Ching, Polypodiodes Ching, Polypodiastrum Ching and Schellolepis J. Sm. as independent taxa according to the results of the present study. It is reasonable to transfer Polypodiodes microrhizoma to Metapolypodium.