中国丝瓣芹属二新记录种:来自ITS序列与形态证据的新见解

Two new records of the genus Acronema(Apiaceae)from China: New insights from ITS sequences and morphological evidence

关键词:  丝瓣芹属, 中国新记录, 多系类群, 界限划分, 分子证据

Key words:  Acronema, new recorded from China, polyphyletic group, delimitation, molecular evidence

摘要:

该文报道了中国伞形科丝瓣芹属植物中国新记录二种——暗伞丝瓣芹(Acronema phaeosciadeum Farille & Lachard)和隐伞丝瓣芹(A. cryptosciadeum Farille & Lachard),描述了二新记录种的形态特征、物候期、生境特点和分布等信息。二者均为Farille所描述,分布于尼泊尔的喜马拉雅高山地区。暗伞丝瓣芹与苔间丝瓣芹(A. muscicola Hand. -Mazz.)相似,但根为细纺锤形,具总苞片和小总苞片,花瓣先端尖,不呈丝状等特征可与后者相区分; 隐伞丝瓣芹与丝瓣芹[A. tenerum(Wall.)Edgew.]相似,区别在于前者根纺锤状,茎生叶少或无,靠近茎基部,花瓣先端不呈丝状。与少辐小芹(Sinocarum pauciradiatum R. H. Shan & F. T. Pu)相比,后者的基生叶回数为三出状三小叶,无小总苞片。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,即隐伞丝瓣芹稳定地嵌套于丝瓣芹属分支内,而暗伞丝瓣芹则位于滇芹分支与亮蛇床族附近。这一发现为丝瓣芹属的系统发育研究提供了新的关键资料。凭证标本存放于江苏省中国科学院植物研究所标本馆(NAS)。

Abstract:

Acronema phaeosciadeum Farille & Lachard and A. cryptosciadeum Farille & Lachard(Apiaceae)are newly reported as occurring in China. Detailed morphological characteristics, phenological periods, habitat characteristics and distribution information of the two species are provided. Both species were originally described by Farille and were known from the high Himalayan regions of Nepal. The discovery of two species expands its known geographical range to southwestern Xizang, China. A. phaeosciadeum is similar to A. muscicola Hand.-Mazz., but differing from the latter by the characteristics, such as thin fusiform root, presence of bracts and bracteoles, and acute petal apices, not-filiform etc. A. cryptosciadeum resembles A. tenerum(Wall.)Edgew., differing in its fusiform root, few or absent stem leaves(when present, close to the stem base), and petals with non-filiform apex. Additionally, compared with Sinocarum pauciradiatum R. H. Shan & F. T. Pu, the latter has trisected basal leaves and lacks bracteoles. To clarify their systematic positions, phylogenetic analysis based on ITS sequences(using both maximum likelihood and Bayesian inference methods)was conducted, delineating their systematic: A. cryptosciadeum is stably nested within Acronema clade, whereas A. phaeosciadeum is situated near the Sinodielsia clade and the Selineae. Notably, the morphological complexity of A. phaeosciadeum combines traits of Acronema(ovoid fruits with indistinct filiform ribs), Sinocarum(non-filiform petals, fusiform roots), and even Sinodielsia or Selineae(e. g., prominent bracteoles), which implies that it may represent a more complex transitional evolutionary stage. The clear placement of A. cryptosciadeum provides strong molecular evidence for its generic assignment. This discovery enriches China's biodiversity inventory, offers critical insights into the taxonomic ambiguity and polyphyletic nature of Acronema, and highlights the importance of cross-regional floristic comparisons in resolving generic delimitation. It further provides crucial new data for the phylogenetic study of the genus Acronema. Voucher specimens are deposited in the Herbarium of the Institute of Botany, Jiangsu Province and Chinese Academy of Sciences(NAS).