Species delimitation and recognition in the Brachycorythis helferi complex (Orchidaceae) resolved by multivariate morphometric analysis

Abstract

The tropical Asian Brachycorythis helferi complex has presented serious identification problems, even after the genus was monographed in 1955. In the present study, morphological variation in the complex was summarized by principal components analysis (PCA) performed on data from herbarium specimens and probable misidentifications were detected by cluster analysis combined with information from protologues and type specimens. Species delimitations are revised accordingly, leading to recognition of five species: B. henryi, B. neglecta (sp. nov.), B. helferi, B. laotica and B. acuta. Brachycorythis obovalis and B. menglianensis are reduced to synonyms of B. acuta and B. henryi, respectively. Description of B. neglecta from Burma and Thailand leaves B. henryi with a much narrower distribution than previously recognized (apparently restricted to the provinces of Guizhou and Yunnan in China and the Shan State in Burma). The names Gymnadenia sesamoides (a synonym of Brachycorythis helferi) and B. laotica are lectotypified, and the latter species is reported as new to Thailand. A dichotomous key to the five accepted species is provided, together with brief descriptions. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162, 64–76.