Zanthoxylum kaokoense (Rutaceae: Zanthoxyloideae), a new species from Angola and Namibia

Zanthoxylum kaokoense, previously mistaken for Z. ovatifoliolatum, is formally described here as a new species. It is a range-restricted species, only known from the Kaokoveld Centre of Endemism, located in southwestern Angola and northwestern Namibia. The species typically grows on arid hillsides, in valleys, and along ephemeral rivers and drainage lines.

Diagnostic characters for Z. kaokoense include its growth as a shrub or small tree, the presence of curved prickles on the branches, petioles, leaf rachises, and some leaflets, as well as fine pubescence (puberulous) on young branches, petioles, rachises, and inflorescence axes. The leaflets are discolorous and contain both marginal and scattered secretory cavities. The inflorescences are either paniculate or racemose-paniculate, and the female flowers have gynoecia with one or two carpels.

Morphologically and genetically, Z. kaokoense is most similar to Z. chalybeum, which is likely its closest relative. The taxonomic status of Z. ovatifoliolatum is still unresolved and will require further fieldwork and comparative analysis, particularly with Z. chalybeum, as the two species may be conspecific. According to IUCN Red List criteria, Z. kaokoense is provisionally assessed as Least Concern (LC) in terms of conservation status.