Acanthopsis ludoviciana H.M.Steyn, 2015

Steyn, Hester M. & Van Wyk, Abraham E., 2015, Taxonomic notes on the Acanthopsis disperma-hoffmannseggiana complex (Acanthaceae, tribe Acantheae), with an interim key to members of the genus, Phytotaxa 219 (1), pp. 1-26 : 10-11

2. Acanthopsis ludoviciana H.M.Steyn , sp. nov. ( Figs. 1 , 3B , 5 )

Acanthopsis ludoviciana differs from A. disperma in being a perennial subshrub with gnarled stems and short internodes (vs. an acaulescent herb), sessile decurrent leaves (vs. petiolated leaves), and a glaucous appearance due to densely packed, short, appressed hairs on the leaves (vs. green leaves with appressed, strigose or spreading hairs). In addition, A. ludoviciana has a lemon-yellow corolla throat (vs. the white throat of both A. disperma and A. adamanticola ). It further differs from A. adamanticola in having sessile, decurrent leaves (vs. petiolated leaves), inflorescences 12–14 mm in diameter (vs. (8–)10– 12(–15) mm in diameter) and a distribution range in the Richtersveld, Northern Cape (vs. the Sperrgebiet in Namibia ).

Type: — SOUTH AFRICA. Northern Cape: Richtersveld National Park, Helskloof Pass amongst Aloe pearsonii , 514 m, (2816 BD), 3 September 2012, Koekemoer 4370 (holotype PRE0861488 -0!; isotypes KMG!, NBG!) .

A. hoffmannseggiana sensu Williamson (2000: 189 fig.), misapplied name, non (Nees) C.B.Clarke.

Perennial, rounded subshrub up to 300 mm high, with gnarled stems and short internodes (<5(–8) mm long). Leaves oblanceolate, 40–60(–80) × 10–15(–20) mm; margin undulate, coarsely dentate spinose, spines rigid, 3–5(–6) mm long, yellowish orange; glaucous with appressed, densely packed short hairs; base attenuate, decurrent, often with tufts of long, silky hairs. Inflorescences 35–60(–75) mm long, 12–14 mm in diameter. Bracts obovate to wedge-shaped, (17–) 20–24 mm long, base 8–11 mm long; middle and upper bracts ending in 5 primary spines, central primary spine usually broadest and compound (with 2 or 3 pairs of marginal secondary spines, occasionally with only 1 pair of marginal spines), lateral spines usually with 1 or 2 basal and 2 or 3 marginal secondary spines; primary spines usually recurved and secondary spines spreading in fruit; bract base pubescent with deflexed to spreading short hairs (often also with scattered long hairs), long, silky hairs adaxially; spines velvety with spreading short hairs interspersed with short glandular hairs (rarely villose—see Notes). Bracteoles sickle-shaped, 7–8(–10) mm long, silky hairy especially towards tip. Calyx tips usually tinged brown, with long, white hairs clearly visible between bracts; dorsal sepal obovate, cuspidate, 11–14 mm long, densely silky hairy, 7–9-veined from base; ventral sepal ovate, 11–13 mm long, densely silky hairy, 5–7-veined from base; lateral sepals 7–8(–10) mm long, densely silky hairy. Flowers blue-purple with lemon-yellow throat; corolla 22–28(–32) × 11–13 mm, tube (6–) 8–10 mm long; central lobe wider than long or equal, constricted at base, truncate to emarginate. Stamens with beige-brown (sometimes purplish) anthers, 2 mm long; filaments 4–5 mm long, glandular. Style with ring of glandular hairs at base. Capsules ovate in face view, flattened, glabrous, shiny, 6–8 × 3–4 mm, 2-seeded. Seeds (4–)5 × 3 mm, covered with long white hygroscopic hairs.

Eponymy: —Named after Louis Johannes Steyn [1999–], the first author’s godson; ludoviciana is the Latinised version of “Louis”.

Distribution, ecology and phenology: — Acanthopsis ludoviciana is centred in the core part of the Gariep Centre of Endemism ( Van Wyk & Smith 2001) and is only known from Helskloof and surroundings in the Richtersveld, Northern Cape, South Africa ( Fig. 1 ). It is endemic to the Succulent Karoo Biome ( Rutherford & Westfall 1994, Low & Rebelo 1996, Mucina & Rutherford 2006) and falls within the Central Richtersveld Mountain Shrubland (SKr 1) vegetation type ( Mucina & Rutherford 2006). This area receives dense fog with associated condensation and the mean annual precipitation (mainly in winter) can be as high as 200 mm, but for most of the areas it is probably less than 90 mm. Acanthopsis ludoviciana grows on mountain slopes between elevations of 240–980 m, and prefers loamy sand to sandy soils derived from weathered granite and quartzite. Flowering time: August and September.

Notes: —Specimens collected from Numees Copper mine and Kodaspiek (Jürgens 10117, Nicholas 2502, Oliver, Tölken & Venter 396 and Venter 8180), have bract spines with densely hairy (villose) margins in contrast to the rest of the specimens with velvety spines.

Conservation status: — Acanthopsis ludoviciana is localised, only known from four populations with an extent of occurrence of 206 km 2. Within this area the species is locally common and the population appears stable. The area is, however, subjected to severe overstocking (mainly goats and sheep) and, should grazing pressure continue to increase, the population is potentially at risk. The species therefore qualifies for Vulnerable under criterion D2 ( IUCN 2001) (L. von Staden, pers. comm. 2014).

Additional specimens examined: — SOUTH AFRICA. Northern Cape: Richtersveld. Kodaspiek , 980 m, (2816 BB), 2 September 1977, Oliver, Tölken & Venter 396 ( PRE!) ; Richtersveld. Kodaspiek , (2816 BB), 1 September 1980, Venter 8180 ( PRE!) ; Richtersveld, Numees Experimental site, (2816 BD), September 1981, Jürgens 10117 ( NBG!) ; Richtersveld ; Helskloof , (2816 BD), September 1953, Munro 1271 ( PRE!) ; Richtersveld ; Numees copper mine ; on rocky mountain side, 244 m, (2816 BD), 27 August 1987, Nicholas 2502 ( PRE!) ; Namaqualand District. Richtersveld National Park. W end of Helskloof Pass , 558 m, (2816 BD), 13 September 2010, Steyn 1815 ( PRE!) ; Namaqualand District. Richtersveld National Park. Helskloof, on turn-off to Paradyskloof , 606 m, (2816 BD), 15 September 2010, Steyn 1818 ( PRE!) ; Hottentotparadysberg ; head of Helskloof , 800 m, (2816 BD), 28 August 1977, Thompson & Le Roux 119 ( NBG!, PRE!) ; Richtersveld ; on top of Hellsberge , (2816 BD), 10 September 1961, Van Breda 1299 ( PRE!) ; Top of Helskloof. Area mountainous, rocky with Mesembryanthemaceae dominant, (2816 BD), 15 September 1977, Van Jaarsveld 2542 ( NBG!) ; Richtersveld National Park, Numees Mountain west of upper Helskloof , (2816 BD), 19 July 2014, Van Wyk 303 ( PRE!) ; Between Gannakouriep Camp and Helskloof turn-off, 385 m, (2817 AC), 13 September 2010, Steyn 1814b ( PRE!) ; Namaqualand District. Richtersveld National Park. Helskloof, on turn-off to Paradyskloof , 493 m, (2817 AC), 15 September 2010, Steyn 1819 ( PRE!) ; Richtersveld, road up SW slope of Vandersterrberg, from Glybank campsite to Koeskopfontein , (2817 AC), 25 August 2014, Von Staden CNR 9138 ( PRE!) .

Figures

FIGURE 1. Known distribution of species within the Acanthopsis disperma-hoffmannseggiana complex. A: A. ludoviciana (●) and A. tuba (Δ), B: A. adamanticola (▲), A. disperma (○), A. dispermoides (□), A. hoffmannseggiana (■) and A. villosa (ۗ).

FIGURE 3. Comparison of floral parts in members of the Acanthopsis disperma-hoffmannseggianna species complex (from left to right): bract(s) (abaxial views), bracteoles, calyx (4 sepals) and flower. A. A. tuba. B. A. ludoviciana. C. A. adamanticola. D. A. villosa. E. A. hoffmannseggiana. F. A. disperma. G. A. dispermoides. Note: if two bracts per species are illustrated, the one on the left is from lower down in the same inflorescence. Scale bar = 10 mm. Vouchers:A = Von Staden CNR 9139 (PRE), B = Koekemoer 4370 (PRE), C = Germishuizen 10074 (PRE), D = Koekemoer 4398 (PRE), E = Steyn 1907 (PRE), F = Koekemoer 4187 (PRE), G = Steyn 1912 (PRE).

FIGURE 5. Acanthopsis ludoviciana: morphology.A–C. Habit. D & E. Leaf indumentum. F–H. Bract. I. Calyx. J. Flower (corolla lobes blue-purple; throat lemon-yellow). K. Glandular hairs at base of style. L. Seed. Vouchers: D, E, G, K, L = Steyn 1814b (PRE), F, H = Koekemoer 4370 (PRE), I, J = Steyn 1818 (PRE). Photographs: M. Koekemoer (A–C).