Abstract
Summary The genus Aerangis Schltr. (Orchidaceae, subfamily Epidendroideae, tribe Vandeae, subtribe Angraecinae) in Madagascar and adjacent archipelagos is revised. Twenty-seven species have been recorded from the region, all of them endemic. Twenty of these are endemic to Madagascar, three to the Comoros only, three to the Comoros and Madagascar and one to Madagascar and Réunion. A third of all Aerangis in the area were assessed to be immediately endangered with 15% Critically Endangered (CR) and 18.5% Endangered (EN). 37% are considered Vulnerable (VU), 15% Near Threatened (NT) and 11% are of Least Concern (LC). Section Microterangis (Schltr.) Hermans is newly established. All the species are described and their typification, history, identification, pollination, distribution and habitat are discussed. The nomenclature and identity of Aerangis citrata (Thouars) Schltr., A. cryptodon (Rchb.f.) Schltr., A. ellisii (B.S.Williams) Schltr., A. hildebrandtii (Rchb.f.) P.J.Cribb & Carlsward, A. ikopana Schltr., A. modesta (Hook.f.) Schltr., A. monantha Schltr., A. polyura (Sander ex Mast.) Hermans and A. rostellaris (Rchb.f.) H.Perrier, are reassessed. Conservation assessments, illustrations and distribution maps are included for all the species. A checklist of the sections, species and a key to their identification are provided. Aerangis bursiculata Hermans is described from the Comoros for the first time.