Coleus serracafemaensis (Lamiaceae), a New Succulent Species from Southwest Angola

Abstract

Coleus serracafemaensis, an ascending sparingly branched shrub with tuberous roots and sky-blue flowers is described here as a new species. It has a restricted range and is only known from Serra Cafema Mountain in southern Angola (within the Kaokoveld Centre of Endemism, southwestern Angola and northwestern Namibia). It grows on granite derived soil among granite boulders in a steep south facing boulder strewn kloof. Diagnostic characters for Coleus serracafemaensis include the large, tuberous rootstock, photosynthesizing stems with peeling bark, distinctly petiolate, broadly ovate to trullate leaves and its large sparingly branched panicles and accrescent sub-equally 5-lobed calyces, each lobe ending in a spine. Coleus serracafemaensis belongs to a group of species previously recognized as belonging to the genus Holostylon which includes 4 species with virgate ascending stems from a perennial base, persistent pedicels breaking near the base of the deciduous fruiting calyx, single flowered cymes and minutely lobed, almost entire style apices. A comparison of some of the more prominent morphological features to differentiate between Coleus serracafemaensis and its possible nearest relative, Coleus gracilipedicellatum, is provided. Based on IUCN Red List categories and criteria, a conservation assessment of Vulnerable (VU D2) is recommended for the new species.