Acanthopsis nitida H.M.Steyn, 2017

Steyn, Hester M. & Van Wyk, Abraham E., 2017, Taxonomic notes on Acanthopsis (Acanthaceae, tribe Acantheae): the group with semi-dense spikes and 5 - fid bracts, Phytotaxa 324 (2), pp. 101-121 : 111-113

3. Acanthopsis nitida H.M.Steyn , sp. nov. ( Figs. 1 , 3C & 6 )

Type: — SOUTH AFRICA. Northern Cape: Namaqualand District. Anenous Pass, S of road, 709 m, (2917 BA), 9 October 2015, Steyn 2129, (holotype PRE 0866187!, isotype NBG!).

Diagnosis: — Acanthopsis nitida differs from all other members of the group with semi-dense spikes and 5-fid bracts in its glossy appearance (not matt), yellow-green puberulent to sub-glabrous leaves (not grey or green strigose to villose leaves) and in having a glabrous (not variously hairy) calyx.

Perennial, compact subshrub, 7–10 cm tall with very short internodes. Leaves sessile, base petiole-like with spines 3–7 mm long; lamina oblanceolate, 40–60(–90) × 8–12 mm, often with yellow-green appearance, puberulent with strigose to spreading short hairs, also with subsessile glandular hairs; apex acute, base attenuate, margin undulate, dentate-spinose, spines rigid, 3–5(–8) mm long, yellow to brown. Inflorescences semi-dense, cylindrical, subsessile, 45–55 mm long, (8–) 10–13 mm in diameter. Bracts broadly obovate to wedge-shaped, (15–) 20–30 mm long (including spines), lamina 8–11 mm long, base obtuse to attenuate; lamina and spines glabrous to puberulent with short white, spreading, hairs and isolated subsessile glandular hairs abaxially, silky-hairy adaxially; middle and upper bracts ending in 5(–7) primary spines; central primary spine often compound with one pair of marginal secondary spines, often simple; lateral primary spines very often with 1 long basal secondary spine (shorter than primary spine) on side facing central primary spine and a short marginal secondary spine on opposite side; spines divergent in flower, spreading to recurved in fruit. Bracteoles linear, 8(–12) mm long, silky-hairy adaxially. Calyx brown-tipped with dorsal sepal ovate, acuminate, 13–15(–16) mm long, glabrous abaxially, silky-hairy adaxially, 7–9(–11)-veined; ventral sepal ovate, 12– 13(–15) mm long, glabrous abaxially, silky-hairy adaxially, 5–7(–9)-veined; lateral sepals 8–9(–10) mm long, glabrous abaxially, silky-hairy adaxially, especially towards base. Corolla lilac to purple with lemon-yellow throat, 25–27 × 10–12 mm, tube 8(–9) mm long, central lobe as wide as long, constricted at the base, emarginate. Filaments 7–8 mm long, glandular; anthers beige, 3 mm long. Style covered with glandular hairs at the base. Capsules 8–9 × 3 mm. Seed 3 × 3 mm.

Etymology: —The specific epithet nitida , meaning “shiny/glossy”, refers to the glossy leaves, floral bracts and calyx of this species.

Distribution, ecology and phenology: — Acanthopsis nitida is endemic to the Northern Cape and is known from three localities in an area to the west of Steinkopf ( Fig. 1 ). It is centred in the core part of the Gariep Centre of Endemism ( Van Wyk & Smith 2001), a biogeographical region rich in restricted-range plants and animals. This distribution falls within the Succulent Karoo Biome ( Rutherford & Westfall 1994, Low & Rebelo 1996, Mucina & Rutherford 2006) in the Richtersveld Bioregion, Anenous Plateau Shrubland ( Mucina & Rutherford 2006) where it receives predominantly winter rains with an average of ± 150 mm per year. The specimens were collected on stony mountain slopes in well-drained sandy soils at elevations of 690–1100 m. Specimens with flowers were collected between August and October.

Conservation status: — Acanthopsis nitida is a range-restricted species (EOO 42 km ²) known from three locations within a small area. It is potentially threatened by habitat loss and degradation due to mining and overgrazing and is categorised as Endangered B1ab(iii) according to the IUCN Red List Category and Criteria ( IUCN 2012) (L. von Staden, pers. comm.).

Additional specimens examined (Paratypes): — SOUTH AFRICA. Northern Cape: Namaqualand District. Anenous Pass, S slope of mountain, 691 m, (2917 BA), 22 August 2012, Steyn 1884 ( PRE) ; Steinkopf District ; Anenous Pass; Approximately 17 km West of Steinkopf ; hills on southern side of the Pass on the old road, 1100 m, (2917 BC), 20 December 1992, Burgoyne 1514 ( PRE) ; Namaqualand District . On dirt road NW of Eyams, 838 m, (2917 BC), 10 October 2015, Steyn 2138 ( PRE) .

Notes: — Acanthopsis nitida can be easily distinguished from the other subshrubs with semi-dense inflorescences in the genus by its glossy appearance (not matt) and yellow-green (not green or grey-green) leaves. Although the central primary spine could be simple or compound (one pair of short, marginal secondary spines), the lateral primary spines always have a basal secondary spine on the side facing the central primary spine.

Figures

FIGURE 1. Known distribution of A. glabra (○), A. scullyi (▲), A. nitida (□), A. glandulopalmata (■) A. insueta (Δ) and A. carduifolia (●). Thunberg’s route (1774) indicated in red. (for explanation see Notes under taxonomic treatment of A. carduifolia)

FIGURE 3. Comparison of floral parts, associated bracts and bracteoles (from left to right): bracts (2), bracteoles (2), calyx (4 sepals: dorsal, ventral and 2 lateral ones) and corolla with anthers.A. A. glabra, B. A. scullyi, C. A. nitida, D. A. glandulopalmata, E. A. insueta, F. A. carduifolia. Note: the bract on the left is from lower down in the same inflorescence. Scale bar = 10 mm. Vouchers:A = Steyn 1893 (PRE), B = Steyn 1911 (PRE), C = Steyn 1884 (PRE), D = Steyn 1890 (PRE), E = Steyn 1805 (PRE), F = Koekemoer 4620 (PRE).

FIGURE 6. Acanthopsis nitida. A & B. Habit. C & D. Leaf indumentum (abaxial). E & F. Bract. G. Calyx. H. Corolla (lobes lilac to purple; throat lemon-yellow). I. Glandular hairs at base of style. J. Capsule. K. Capsule with seed. Vouchers: C–I = Steyn 1884 (PRE), J = Burgoyne 1514 (PRE), K = Steyn 2129 (PRE). Photographed by: M. Koekemoer (A & B) and H.M. Steyn (C–K).