Local variation of leaf morphology in Bulbophyllum drymoglossum (orchidaceae)

Abstract

In Japan, Bulbophyllum drymoglossum is a unique species without pseudobulbs in the genus Bulbophyllum. A normal form of B. drymoglossum was described as having an obtuse leaf tip and unclear midrib but we found many B. drymoglossum individuals with an acute leaf tip adding clear midrib in Kochi Prefecture, Japan. It is questionable whether the individuals having an acute leaf tip and/or a clear midrib are simply morphological variants of this species. To reveal the status of the individuals, we performed morphological and molecular analyses using B. drymoglossum having acute/obtuse leaf tips and clear/unclear midribs and two related sympatric species, B. inconspicuum and B. japonicum. Morphological analyses showed that B. drymoglossum with an acute leaf tip had a longer leaf and rhizome internode than those with an obtuse leaf tip, though the two types of leaf tip shape of B. drymoglossum overlapped with the two character ranges. Individuals of B. drymoglossum with unclear midribs were twice as many as those with clear midribs regardless of leaf tip shape. Molecular analysis showed no evidence of genetic differentiations between the two types of B. drymoglossum. Because a local floral variation of B. drymoglossum (described as B. somai) was reported from Taiwan, this species might have various morphological variations adapted for local regions.