Premna sebrabergensis Swanepoel, Van Jaarsv. & A.E.van Wyk, sp. nov. (Figs 1–4)

Diagnosis:— A woody shrub or tree, morphologically resembling Premna senensis and P. sulphurea. It differs from P. senensis in being smaller, up to 3 m tall (vs. up to 6 m); indumentum on vegetative parts consisting of scattered simple trichomes, curved, antrorse, and minute yellow glandular scales (vs. spreading pilose, trichomes simple or multicellular, scales absent); leaves opposite (vs. opposite or 3-whorled), lamina ovate, rarely elliptic, attenuate to acuminate or acute towards apex (vs. ovate, oblong or obovate to suborbicular, rounded or acuminate); inflorescences paniculately arranged cymes (vs. open corymbs), indumentum similar to vegetative parts with straight simple trichomes in addition (vs. pubescent, lacking scales); calyx distinctly 5-lobed (vs. distinctly to obsoletely 4-lobed); corolla tube shorter than calyx [two thirds the length] (vs. longer [ca. twice as long]), corolla lobes puberulous abaxially (vs. glabrous); stamens not exceeding corolla lobes (vs. exceeding), filaments 1.1–1.3 mm long (vs. longer, ca. 3.5 mm). It differs from P. sulphurea in having the indumentum on vegetative parts consisting of white antrorsely-directed, simple trichomes, and minute, yellow, glandular scales (vs. tawny stellate tomentose trichomes); lamina narrowly to broadly ovate, rarely elliptic (vs. oblong or obovate-oblong), shorter, 10–78 mm long (vs. 75–150 mm); calyx lobes acute (vs. rounded or obtuse); corolla cream-white or green-white (vs. sulphur-yellow or whitish violet); stamens inserted near throat of corolla tube (vs. below the middle).

Type:— NAMIBIA. Kunene Region: Zebra Mountains, ca. 2.5 km from Etemba along track to Enyandi, amongst boulders, 1713 BA, 740 m a.s.l., 27 April 2025, Swanepoel 661 (holotype WIND!; isotypes LUBA!, PRE!, PRU!).

Woody shrub or small tree up to 3 m tall; all vegetative parts with scattered to dense, white, curved, antrorsely-directed, simple trichomes, and minute, yellow, glandular scales; crushed leaves with no distinctive scent. Stems single or multi-stemmed from just below or above ground level, cylindrical; bark longitudinally ridged, fissured on older stems, grey-brown; branches furrowed, sometimes peeling in filiform strips; older branches dark brown with tawny lenticels; young branches green, becoming light brown. Leaves thin, soft, opposite and decussate; petiole slender, terete, slightly grooved, 4–25 mm long; lamina narrowly to broadly ovate, rarely elliptic, usually attenuate to acuminate towards apex, apex obtuse or acute, base cuneate, flat to conduplicate, (10–)30–40(–78) × (4–)15–20(–37) mm, green to yellow-green (due to yellow scales), slightly discolorous, margins entire, often undulate, or especially on long shoots coarsely dentate or crenate-dentate, midrib and 3–7 principal lateral veins each side prominently raised abaxially, simple trichomes rarely almost absent adaxially. Inflorescences terminal with flowers in cymes paniculately arranged, up to 50 mm long; bracts and bracteoles narrowly triangular, bracts up to 2.5 mm long, bracteoles up to 1 mm long, indumentum similar to vegetative parts but with straight simple trichomes usually in addition. Flowers hermaphrodite; pedicels up to 3 mm long. Calyx with indumentum abaxially similar to vegetative parts, adaxially glabrous; tube cupuliform, 2-lipped, 2.1–2.3 mm long, ca. 1.4 mm diam., fruiting calyx somewhat enlarged, cupuliform, prominently reticulately nerved; lobes 5, distinct, narrowly triangular to triangular, 0.5– 0.9 mm long, the 2 lobes on anterior side slightly longer than the 3 lobes on posterior side. Corolla cream-white or green-white, 2-lipped, not-aromatic when crushed; tube cylindric, ca. 2.1 mm long, 1.3 mm diam., glabrous, villous inside near throat, trichomes white, submoniliform (visible in fresh material), shorter than stamens; lips puberulous towards apex abaxially, margins entire or irregularly crenulate, posterior lip emarginate, ovate or suborbicular, ca. 1.8 × 1.5 mm, ciliate, sub-cucullate, erect, forming a hood over anthers; anterior lip 3-lobed, lobes on specific flower all similar or polymorphic, oblong, ovate, elliptic or triangular, spreading, 1.3–1.6 × 0.8–1.0 mm, median one largest. Stamens didynamous, inserted near throat of corolla tube, exserted ca. 1 mm; filaments tapering, short filament ca. 1.1 mm long, long filament ca. 1.3 mm long; anthers dorsifixed, reniform, ca. 0.3 × 0.5 mm, pale to dark brown or orange, thecae elliptic, divergent. Gynoecium ca. 4 mm long; ovary ovoid or globose, 0.9–1.1 × 0.8–1.0 mm diam., with dense globose glands towards apex and subtended by a brownish tissue (nectary/disc?) at the base (Figs 4F & 4G), 4-locular with 1 ovule per loculus; ovules narrowly ovoid, ca. 0.5 mm long; style filiform, ca. 3 mm long, equal to or slightly exceeding stamens, stigma shortly 2-fid with minute papillae. Fruit drupaceous, obovoid or globose when mature, ca. 5 mm diam., mesocarp including exocarp thin, fleshy, black, endocarp broadly obovoid, saccate-like (sensu Satthaphorn et al. 2025).

Phenology:— Flowers and fruit have been recorded from April to June (late summer to winter).

Distribution and habitat:— Currently, Premna sebrabergensis is only known from four localities in the Kaokoveld Centre of Endemism, southwestern Angola and northwestern Namibia, specifically in the Zebra Mountains of Namibia and its continuation in Angola (Fig. 5). It typically inhabits plains and hillsides, primarily thriving in clay soils derived from the Kunene Igneous Complex, which includes dark leucotroctolite, olivine-bearing anorthosite, dunite, gabbro and norite (Miller et al. 1980, Maier et al. 2013). The species is found at elevations ranging from 870 to 925 m a.s.l., ca. 165–225 km inland from the Atlantic Ocean. The region receives an average annual rainfall of 250 to 350 mm, mainly during the summer months (Atlas of Namibia Team 2022). However, it is possible that the species has a wider distribution within the Zebra Mountains, as many areas remain difficult to access.

Conservation status:— Premna sebrabergensis has been recorded at only four localities where it is rare to locally common. Although a brief search at various other localities with seemingly suitable habitat did not reveal any plants, it is probably more widespread than currently known (see under ‘Distribution and habitat’ above). The extent of occurrence (EOO) has been calculated as 1012 km ² and the area of occupancy (AOO) as 20 km ², based on a cell width of 2 km as recommended by the IUCN Standards and Petitions Committee (2024). Due to its limited geographical range (AOO <500 km ²), with only four known localities and habitat under pressure from prolonged drought conditions, Premna sebrabergensis is here provisionally assessed as Endangered EN B2a,b(iii) (IUCN 2012).

Etymology:— The specific epithet refers to the Zebra Mountains, known as Sebraberge in Afrikaans, located in northwestern Namibia and southwestern Angola, where Premna sebrabergensis is exclusively found.

Notes:— Premna sebrabergensis has been confused with Volkameria glabra in the herbarium. However, apart from being from a different genus, it can be differentiated from the latter by the indumentum (presence of yellow scales, the latter retaining their colour in herbarium specimens [vs. scales whitish, but turning blackish upon drying to give the leaves a punctate appearance]), leaves opposite (vs. usually 3-whorled, occasionally opposite), lamina usually attenuate to acuminate towards apex (vs. acute or obtuse), corolla tube ca. as long as the calyx tube, ca. 2.2 mm (vs. 2–4 times as long, 4–8 mm), corolla lobes much shorter, posterior lobe (lip) erect, forming a hood over stamens, 1.3–1.8 mm long (vs. lobes spreading i.e. not hood-forming, 3–4 mm long), stamens pale green, barely exserted from corolla tube, ca. 1 mm long (vs. mauve or lilac, long exserted, 5–7 mm) and the fruit which is black when mature, smaller, ca. 5 mm diam. (vs. cream, 6–10 mm diam).

It is unlikely that the new species will be confused with any of the other species of Premna in Angola: Premna angolensis has the leaves ternate, quaternate or opposite (vs. opposite), the calyx truncate or scarcely lobed (vs. distinctly triangular lobed); indumentum on vegetative parts of P. congolensis lacks scales (vs. scales present), the inflorescence is corymbiform (vs. flowers in cymes paniculately arranged), the corolla tube is ca. double the size (ca. 4 mm long) (vs. ca. 2.1 mm); P. polita has the inflorescence umbellate-corymbose (vs. flowers in cymes paniculately arranged) and the fruit glandular-puberulous all over (vs. with sparsely scattered minute globose glands towards apex).

Additional specimens examined (paratypes):— ANGOLA, Cunene Province:—1613: Serra Cuio, 25 km southeast of Oncocua along track to Chitado, 870 m, (– DC), 3 May 2015, Swanepoel 659 (LUBA!, PRU!); Serra Uanguembela, 32 km east-southeast of Oncocua along track to Chitado, 917 m, (– DD), 25 April 2016, Swanepoel 660 (LUBA!, PRU!).

NAMIBIA, Kunene Region:—1713: On rocky outcrop near baobab, 925 m, (– AD), 10 March 2003, Hoffman LH 875 (WIND!); Zebra Mountains, valley ca. 6 km south of Ombuku, 880 m, (– AD), 27 May 2012, Swanepoel & Van Jaarsveld 657 (WIND!); Zebra Mountains, valley ca. 7 km south of Ombuku, 890 m, (– AD), 6 May 2013, Swanepoel 658 (WIND!).