Journal of Plant Research

, Volume 132, Issue 1, pp 19–31 | Cite as

Two new genera of Podostemaceae from northern Central Laos: saltational evolution and enigmatic morphology

  • Satoshi KoiEmail author
  • Hyosig Won
  • Masahiro Kato
Regular Paper


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.


Ctenobryum Enigma Laosia matK phylogeny New genera Saltational evolution 



We thank M. Nuraliev for providing information and images of Laosia ramosa, P. Werukamkul for help on the field trip, and Y. Hirayama for technical assistance for the phylogenetic analysis. This study was supported by KAKENHI Grant Number JP26870502 and the Osaka City University Strategic Research Grant 2017 for young researchers to SK.

Supplementary material

10265_2018_1082_MOESM1_ESM.pdf (168 kb)
Supplementary material 1 (PDF 168 KB)


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Copyright information

© The Botanical Society of Japan and Springer Japan KK, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Botanical Gardens, Faculty of ScienceOsaka City UniversityKatanoJapan
  2. 2.Department of Biological ScienceDaegu UniversityGyungsanKorea
  3. 3.Department of BotanyNational Museum of Nature and ScienceTsukubaJapan

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