Towards a monograph of membranaceous Vanillas: a nomenclatural revision of Vanilla subgen. Vanilla (Vanilloideae, Orchidaceae)

Background and aims – Vanilla subgenus Vanilla was established by Soto-Arenas and Cribb (2010) to include Neotropical species characterized by membranaceous leaves, a labellum without a penicillate callus, and a column attached solely at the base of the lip. Vanilla mexicana (= Epidendrum vanilla) was the first species attributed to this subgenus, and its nomenclature traces back to the Vanilla’s taxonomic origins, serving as the type species for the entire genus. Despite this, several biological aspects of membranaceous vanilla species remain poorly studied, including their taxonomy and nomenclature, which have not been thoroughly addressed. The lack of clarity regarding the circumscription of these fairly rare taxa has led to taxonomic confusion and neglect by botanists. This study aims to conduct a typological assessment of all names associated with Vanilla subgen. Vanilla. Material and methods – A comprehensive list of names attributable to Vanilla subgen. Vanilla was compiled from different sources. Protologues were studied for every name and type specimens were examined through direct visits or virtual herbaria. The International Code of Nomenclature of algae, fungi, and plants was followed for the type designation and nomenclatural notes. Key results – A comprehensive nomenclatural revision was carried out for 29 names. A total of eight lectotypes and one epitype are designated, with nomenclatural notes provided for most names within the subgenus.