Keetia gordonii sp. nov. (Rubiaceae - Vanguerieae), a new species of threatened forest liana from Gabon

Keetia gordonii sp. nov. (Rubiaceae - Vanguerieae) a new species of forest liana from Gabon, is described and illustrated. The new species shows all the diagnostic characters of Keetia, such as pyrenes opening by an apical cap and seeds with tanniniferous endosperm, both of which are unrecorded in other genera of the tribe, flowers with a long-exserted style and erect anthers and a (usually) climbing habit. However, it is unique in the genus for its corolla with dense, appressed, brown hairs externally (vs glabrous or with a few hairs towards the apex), its glabrous disk (vs variously pubescent) and its seeds with a continuous tanniniferous layer in the outer part (vs with tanniniferous areas forming radial bands, or diffuse). Keetia gordonii is assigned to the Keetia hispida group of Guineo-Congolian African species. It is the first endemic Keetia species to be described from Gabon, although several others are awaiting description. On current evidence, the species appears to have six locations and is threatened by forest clearance. It is provisionally assessed using the IUCN (2012) standard as Vulnerable [VU B2ab(i,ii,iii,iv,v)].