Synopsis of the genus Vitex (Lamiaceae) in the Democratic Republic of the Congo

The genus Vitex L. (Linnaeus 1753: 638 “938”) comprises some 250 species almost all in tropical regions (Mabberley 2017). Until recently, Vitex was classified in Verbenaceae, subfamily Viticoideae (Briquet 1895). Harley et al. (2004) conclusively showed that Viticoideae are better placed in Lamiaceae. Very recently, subfamily Viticoideae has been restricted to three genera by new molecular phylogenetic evidence (Li et al. 2016). Vitex is the only genus of the subfamily present in Africa. The genus Vitex awaits revision in Africa (Cabral 2013). The most comprehensive account is still Pieper’s (1928) revision. Moldenke compiled much information in his “Materials towards a monograph of the genus Vitex”, which has not always contributed to taxonomic clarification (Moldenke 1955a, 1955b, 1956, 1957, 1958a, 1958b). Vitex has recently been revised for the Flora of Tropical East Africa (FTEA) (Verdcourt 1992), and for Flora Zambesiaca (FZ) (Sales 2001, 2005). For the Democratic Republic of the Congo (D.R. Congo), the most recent account of Vitex dates back to De Wildeman (1929a). In order to prepare the treatment of the genus Vitex for the Flore d’Afrique centrale (FAC; see Sosef 2016), I have revised all the material from D.R. Congo. During that work, a number of taxonomic and nomenclatural issues had to be solved, with implications beyond the borders of FAC, an account of which is given in the present note. I present here a key to the species, and a check-list with a revised synonymy. When my taxonomic treatment departs from FZ and FTEA, a concise justification is provided. New combinations are coined when necessary and new synonyms are reported. Lectotypifications were necessary in a number of cases. For each taxon, a brief description is provided, focused on diagnostic traits. Detailed accounts of the taxa, including citation of specimens studied, will be published in the Flore d’Afrique centrale.