Anew review of the Western Indian Ocean genus Danais (Rubiaceae: Danaideae), with seven new species from Madagascar

Danais Comm. ex Vent. ( Rubiaceae ) comprises about 49 species in Madagascar, the Mascarenes, and East Africa. A new species taxonomy is presented here, with an updated description and key to all Danais species, details of taxonomic changes, and lectotypifications. Four previously described species that were excluded from Danais are reinstated here: D. aptera Wedd. ex Homolle, D. baccata Homolle, D. coerulea Homolle ex Cavaco, and Sabicea verticillata Wernham under the replacement name Danais confusa C.M. Taylor. Identities and circumscriptions of some previously described Danais species are revised. The taxonomic circumscription of D. aurantiaca Baker is narrowed by the separation of a new species, D. reticulata C.M. Taylor; D. cernua Baker is diagnosed here by some different characters; D. fragrans (Lam.) Pers. in the Mascarenes is separated from plants of Madagascar formerly included in this species, now named D. lyallii Baker; D. longipedunculata Homolle and D. masoalana C.M. Taylor are no longer distinguishable and are synonymized; D. nigra Homolle is narrowed by the separation of the new species D. puffiana Razafim. & C.M. Taylor; D. perrieri Homolle is distinct from D. nigra Homolle; and D. terminalis Boivin ex Drake is still poorly known, but its circumscription is clarified and narrowed. Seven new species of Danais are described: D. coriacea C.M. Taylor, D. gracilis C.M. Taylor, D. ovata C.M. Taylor, D. puffiana Razafim. & C.M. Taylor, D. reticulata, D. sambiranensis C.M. Taylor, and D. schatzii C.M. Taylor. All the new species are threatened using the IUCN Red List Criteria: two are preliminarily assessed as "Critically Endangered" and five as "Endangered".