A Synopsis of the Rattans (Arecaceae: Calamoideae) of Laos and Neighbouring Parts of Indochina

Abstract

A revised taxonomy is presented for the rattans of Indochina, defined here as Laos, Vietnam, Cambodia, Xishuangbanna Prefecture (Yunnan, China) and Thailand (excluding the South-west and Peninsula). The study is based on extensive recent collections from Laos, together with examination of existing herbarium material from the rest of Indochina and surrounding regions. The quality of coverage is reviewed. Twenty-one species are still known in Indochina from five or fewer specimens; these require further collecting, as do some taxa where taxonomic difficulties remain. Coverage of Vietnam is relatively poor in this study and a review of in-country herbarium material there is recommended. Further fieldwork is most needed in and around the Annamite mountains of Laos, Vietnam and Cambodia. On the basis of morphological comparisons, fifty species are now confirmed to occur in Indochina, plus one distinctive, as-yet unnamed taxon of Korthalsia ('taxon A') which probably merits species status. Eight of these fifty species have been discovered recently and named elsewhere. Many taxa previously recorded from Indochina have been placed in synonymy, mainly as a result of better understanding of the range of variation in living individuals and wild populations. Some taxonomic changes cover Sundaic forms or Chinese forms not occurring in Indochina. Six names of uncertain application are discussed. Taxonomic difficulties remain for several taxa, especially the larger cirrate Calamus species and those species close to Calamus tetradactylus. A list of all identified specimens is given. Distributions are reviewed in detail, based on a re-examination both of specimens and of published locality data. New records are provided for many species for many parts of Indochina, especially Laos but also other countries. Some new island records are also given for Calamus tenuis and C. viminalis in Sumatra, Java and Bali. A number of past published country records for Thailand, Laos, Vietnam and Cambodia are now considered to be misidentifications or a result of geographical errors. There are ten valid species for which all published reports for Indochina are now thought to be in error. In addition to taxonomic and distributional information the first full, published description of Calamus rhabdocladus is given and substantial modifications are made to previous descriptions of Calamus dioicus and C. kingianus, Identification criteria are discussed and refined for many species. A key to fertile herbarium material is given and five species are illustrated. Information from Indochina on habitat, local names, uses and conservation status is given where available. As well as several very localised species the conservation status of the widespread, heavily-harvested, solitary-stemmed Calamus poilanei is also believed to be especially poor.