中国叶下珠科植物新资料

New taxa of Phyllanthaceae from Guangxi, China

关键词:  叶下珠科, 山格木属, 余甘子属, 新种, 广西

Key words:  Phyllanthaceae, Cathetus, Emblica, new species, Guangxi

摘要:

广义叶下珠属为叶下珠科的核心类群,在生活型、花部、种子及花粉形态上呈现出高度多样性,表明该属并非单系类群。近年来基于分子系统学与形态学证据的研究已将广义叶下珠属划分为 10 个单系属。该文报道了中国叶下珠科1新种和1新记录种,即长丝山格木(Cathetus filipes D. X. Nong, B. Y. Huang & Z. Xiong)(新种)和卵叶余甘子 [Emblica pacoensis (Thin)R. W. Bouman](新记录种),描述其形态特征、物候期及分布等信息,二者均生长于中国西南部和越南北部的岩溶山地。长丝山格木与滇藏叶下珠 [Cathetus clarkei(Hook. f.)R. W. Bouman]相似,但小枝通常呈红褐色,花梗和果梗均较长,花丝长达3 mm,下部合生,上部分离,合生部分长约2.5 mm,柱头较长等特征可与后者相区分; 卵叶余甘子与西南叶下珠 [Emblica tsarongensis (W. W. Sm.)R. W. Bouman] 近似,区别在于前者叶片圆形、卵形或卵状披针形,叶脉在上面凸起,花序由1朵雌花和数朵雄花组成聚伞花序。基于ITS序列的系统发育分析(最大似然法和贝叶斯推断)进一步明确了二者的系统位置,即长丝山格木位于山格木属分支,卵叶余甘子则位于余甘子属分支。该发现丰富了中国叶下珠科植物多样性,更正了馆藏标本的错误鉴定,对岩溶地区植物区系和演化研究具有重要意义。

Abstract:

Phyllanthus sensu lato(s. l.)is the core group of Phyllanthaceae and exhibits high diversity in life form, floral, seed and pollen morphology, indicating that the genus is not monophyletic. Recent studies based on molecular and morphological data have segregated Phyllanthus s. l. into ten monophyletic genera. In this study, one new species and one newly recorded species of Phyllanthaceae from Guangxi, China are reported, namely Cathetus filipes D. X. Nong, B. Y. Huang & Z. Xiong, and Emblica pacoensis(Thin)R. W. Bouman(newly recorded). Both species occur in karst mountains of southwestern China and northern Vietnam. Detailed morphological descriptions, phenology and distribution information are provided. Cathetus filipes is morphologically similar to C. clarkei(Hook. f.)R. W. Bouman, but differs by its usually reddish-brown branchlets, distinctly longer pedicels, filaments up to 3 mm long, connate in the lower about 2.5 mm and free above, and longer stigmas. Emblica pacoensis is similar to E. tsarongensis(W. W. Sm.)R. W. Bouman, but can be distinguished by its orbicular, ovate or ovate-lanceolate leaves with veins raised adaxially, and cymes consisting of one female flower and several male flowers. Phylogenetic analyses based on ITS sequences, using maximum likelihood and Bayesian inference, confirm the phylogenetic positions of the two species: Cathetus filipes is nested in the Cathetus clade, whereas Emblica pacoensis falls into the Emblica clade. These discoveries enrich China's biodiversity inventory of Phyllanthaceae, correct previous misidentifications of herbarium specimens, and are significant for understanding the floristic composition and evolution of plants in karst areas.