Novelties among East African angraecoids (Orchidaceae, Angraecinae)

Abstract

Here we describe and illustrate two new species of angraecoid orchids from East Africa, Tridactyle delepierrei and Ypsilopus iversenii, respectively from Albertine Rift (Rwanda and Uganda) and west Usambaras (Tanzania). The first species is closely allied to the three species of Tridactyle sect. Eggelingiae and to Tridactyle nalaensis. The second species is closely related to Y. leedalii from the southern highlands of Tanzania, and the affinities of these two species to other Ypsilopus are discussed. Diagnostic and morphological characteristics of these new species along with identification keys are provided, including those for the species of Tridactyle from East Africa and the Albertine Rift, and for the species of Ypsilopus sect. Ypsilopus. These new species are threatened with extinction based on the categories of the IUCN Red List, with T. delepierrei suggested to be Endangered (EN B1), while Y. iversenii would be Critically Endangered (CR). Our findings highlight the need for further orchidological inventories and taxonomical studies to support evidence-based conservation and management of the remaining montane forests of East Africa.