Warneckea austro-occidentalis, a new species from Cameroon and Nigeria, and re-evaluation of W. fascicularis var. mangrovensis (Melastomataceae-Olisbeoideae) R. Douglas Stone 1 , Jean-Paul Ghogue 2 & Martin Cheek 3 Summary. Described and illustrated is Warneckea austro-occidentalis R. D. Stone, an endemic of tropical forests in Cameroon’s South West Province and adjacent Nigeria. The name W. mangrovensis (Jacq.-Fél.) R. D. Stone is also proposed at species level for the taxon originally described as W. fascicularis var. mangrovensis Jacq.-Fél. An IUCN (2001) status of endangered is assigned for both W. austro-occidentalis and W. mangrovensis. Key Words. Africa, Cameroon, Gabon, Melastomataceae, Nigeria, Warneckea. Introduction Warneckea Gilg (c. 50 spp.) is a genus of shrubs and small trees inhabiting humid forests in Africa, Madagascar, and Mauritius. From the closely related Memecylon L. (300+ spp., Old World tropics) it can usually be distinguished by the strongly tri- or multinervate leaves that are reminiscent of other Melastomataceae (Jacques-Félix et al. 1978; Jacques-Félix 1978; Stone 2004). Memecylon on the other hand has apparently uninervate leaves, except for certain species in which the leaves are “subtrinervate” (sensu Jacques-Félix 1979: 424; Stone et al. 2008). Other memecyloid taxa with strongly trinervate leaves include Spathandra Guill. & Perr. (1 sp., W & C Africa) and Lijndenia Zoll. & Moritzi (c. 15 spp., W and E Africa to Madagascar and Indo-Malesia). From these genera, Warneckea is differentiated by inflores- cence axes glabrous (not puberulent as in Spathan- dra), calyx lobes well-developed, ovary imperfectly 2-loculed, embryo with fleshy cotyledons, and leaves mostly smooth on drying (not granular or roughened) with conspicuous veinlets in a reticulate-areolate pattern (Jacques-Félix 1977, 1978; Jacques-Félix et al. 1978; Stone 2004). Added support for maintaining Warneckea as a distinct genus is provided by phylogenetic analyses of the nuclear GapC gene (Stone 2006). The infrageneric relationships and historical biogeography of Warneckea are now under investigation (Stone 2007; Stone & Andreasen 2009). In this paper we describe a new species of Warneckea and propose another new combination at species rank, based on recent field work in Cameroon supplemented by comparative studies of herbarium material. All specimens cited have been seen unless otherwise indicated. Conservation assessments are presented for both species according to the criteria of IUCN (2001). A New Warneckea from Cameroon and Nigeria Warneckea austro-occidentalis R. D. Stone, sp. nov. a W. pulcherrima (Gilg) Jacq.-Fél. et W. memecyloidi (Benth.) Jacq.-Fél. combinatione: petioli 7 – 10 mm longi (non 2 – 5 mm), paginae foliorum basi cuneatae vel rotundatae (numquam cordatae), inflorescentiae in nodis ramorum vetustiorum fasciculatae (non axillares), pedunculi 1.7 – 3.2 cm longi, petala alba (non caeruleo-violascentes), fructus majores (15 – 16 × 10 – 11 mm non 10 – 11 × 6 – 8 mm) distinguenda. Typus: Cameroon, South West Province, Bolo forest, near Konye, 5 km W of Kumba-Mamfe road, 4°55 ′ N, Accepted for publication February 2009. 1 School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X01, Pietermaritzburg 3209, South Africa. e-mail: StoneRD@ukzn.ac.za 2 Herbier National du Cameroun, B.P. 1601 Yaoundé, Cameroun. e-mail: jpghogue1062@yahoo.fr 3 Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK. e-mail: m.cheek@rbgkew.org.uk KEW BULLETIN VOL. 64: 307–312 (2009) © The Board of Trustees of the Royal Botanic Gardens, Kew, 2009