Abstract
Summary Species new to science discovered from the Banyang Mbo Wildlife Sanctuary (BMWS) of SW Region Cameroon are reviewed and summarised, as are species listed as threatened which have been recorded, both from lowland evergreen forest and cloud (submontane) forest. In total, five globally Critically Endangered, 17 Endangered and 21 Vulnerable plant species are listed for BMWS. We describe an additional, narrow endemic of BMWS, Tricalysia banyangmbo sp. nov. (sect. Tricalysia Rubiaceae-Coffeeae), similar in the subulate calyx lobes exceeding the calyx tube and in the stems being densely, patently, shortly hairy, to T. sylvae Robbr. of Littoral, South Region, Cameroon and Gabon. The new species differs in having stipules in which the awn is shorter than the blade (vs vice versa), the leaf bases are rounded (vs cordate), the blades lack domatia (vs present), the flowers are 4 (– 5)-merous (vs 5 – 6-merous) and the anthers lack a distinct and conspicuous, apical connective appendage (vs present). The new species is known from three collection sites with an estimated area of occupation of c. 4 km 2 and is in an area threatened by oil palm plantations. We provisionally assess the species with the 2012 IUCN standard as Critically Endangered [CR B1ab(iii) + B2ab(iii)].