Clarifying the dubious identity of Vanilla dubia Hoehne (Orchidaceae) and its relatives

Abstract

Background and aims – Brazil has more than 40 species of Vanilla. Some taxa have been considered to be obscure since they are known only from the type specimen. This is the case of some south-eastern Brazilian species such as V. dubia and V. dungsii. While studying the diversity of Brazilian Vanilla, plants of an unidentified species were found in Ubatuba, São Paulo, Brazil. After flowering, it was confirmed that the species corresponded to the obscure V. dubia. Material and methods – A redescription of V. dubia is provided and a morphological comparison with the related taxa V. dungsii and V. paulista is presented. An illustration of V. dubia is provided, and its geographic distribution is presented. The identity of the enigmatic V. dungsii is also clarified based on holotype examination and on images of living specimens. Key results – Vanilla dubia is recognized by its coriaceous leaves with prominent vascular bundles in transverse section, by its white 3-lobed labellum with yellow lobes and undulate-crenulate margins, and by its tuberculate appendages on the apical portion of the labellar crest. Morphological characteristics suggest a close relationship of V. dubia with V. dungsii and V. paulista. Vanilla dubia occurs in the Dense Ombrophilous Forest, while V. paulista occurs in the Semi-deciduous Mesophytic Forest, and V. dungsii is endemic to the Dense Montane Ombrophilous Forest. Based on current data, V. dubia is assessed as Endangered. Conclusion – Evaluation of vegetative and reproductive characters from living and herbaria specimens is crucial to understanding the identity and species boundaries of Vanilla. The data presented here show that the species occurring in the Atlantic Forest, V. dubia and V. dungsii, are more closely related to each other than to V. paulista, which occurs in Semi-deciduous Mesophytic Forests. A proposal to change the status of V. dungsii as a subspecies of V. dubia can be further considered.