Koi Satoshi, Won Hyosig, Kato Masahiro
Botanical Gardens, Faculty of Science, Osaka City University, Katano, Osaka, 576-0004, Japan.
Department of Biological Science, Daegu University, Gyungsan, Gyungbuk, 38453, Korea.
J Plant Res. 2019 Jan;132(1):19-31. doi: 10.1007/s10265-018-01082-7. Epub 2019 Jan 9.
Podostemaceae, the river-weeds, are characterized by remarkable differences between species and genera, which resulted from saltational evolution. This paper presents additional cases of such two genera, which are described here from the Phou Khao Khouay National Protected Area in northern Central Laos. Molecular phylogenetic data show that Ctenobryum mangkonense (gen. & sp. nov.) is sister to Hydrodiscus koyamae, while Laosia ramosa (gen. & sp. nov.) is isolated from all Asian genera of subfamily Podostemoideae. Ctenobryum mangkonense is distinct from Hydrodiscus koyamae in the crustose roots (versus rootless in the latter), scattered flowers on the root (versus alternate on the shoot), and pectinate bracts (versus simple, sheath-like). Laosia ramosa is distinct from all the genera in the columnar, endogenously branched axes and single style-stigma complex. The axis is an enigmatic organ with combined characteristics of root, stem and leaf, pending further study. Laos, together with Thailand, is a center of diversity of the Southeast and East Asian Podostemoideae. The three monotypic genera, i.e., Ctenobryum, Hydrodiscus and Laosia, occur in neighboring and closely similar aquatic habitats within the Area. The new taxa are formally described.
川苔草科，即河苔草类植物，其特点是物种和属之间存在显著差异，这是由跳跃式进化导致的。本文介绍了该科另外两个属的情况，它们是在老挝中北部的普乔考伊国家保护区发现并在此描述的。分子系统发育数据表明，曼孔梳苔草（新属及新种）是小山川盘草的姐妹种，而分枝老挝苔草（新属及新种）与川苔草亚科的所有亚洲属都不同。曼孔梳苔草与小山川盘草的区别在于其具壳状根（后者无根）、根上花散生（而不是茎上花互生）以及栉齿状苞片（而非简单的鞘状苞片）。分枝老挝苔草与所有属的区别在于其柱状、内生分枝的轴以及单一的花柱 - 柱头复合体。该轴是一种具有根、茎和叶综合特征的神秘器官，有待进一步研究。老挝与泰国一样，是东南亚和东亚川苔草亚科的一个多样性中心。这三个单种属，即梳苔草属、川盘草属和老挝苔草属，出现在该区域内相邻且极为相似的水生栖息地中。文中正式描述了这些新分类群。
