Acanthopsis dispermoides 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 : 23-25

7. Acanthopsis dispermoides H.M.Steyn , sp. nov. ( Figs. 1 , 3G , 10 )

Acanthopsis dispermoides can be distinguished from A. disperma by being a biennial or perennial (vs. an annual herb), with subsessile (petiole 2mm long) to sessile leaves (vs. petiolated leaves; petiole 3–10 mm long) and a distribution which is restricted to the Western Cape (vs. Namibia and Northern Cape, South Africa), and from A. hoffmannseggiana , its closest neighbour (and probably relative) occurring to the north of the Swartberg Mountains in the Great Karoo, by the much shorter (sub-sessile; <0.2 mm long) glandular hairs on the bracts (vs. 0.2–0.3(–0.4) mm long), the strigose to appressed leaf indumentum (vs. spreading glandular hairs) and the narrower ((8–) 10–12 mm in diameter) inflorescences (vs. (12–)15–18(–20) mm in diameter).

Type: — SOUTH AFRICA. [Western Cape]: Little Karoo. Eastern foothills of Warmwaterberg. Lot 2, near spring, 600 m, (3320 DD), 21 August 1971, Boucher 1560 ( PRE 40576 ) (holotype PRE0129553 -0!; isotype NBG0274662 -0!) .

A. disperma sensu Vlok & Schutte-Vlok (2010: 187 fig.), misapplied name, non Nees.

Biennial or perennial acaulescent herb, rarely a subshrub with reduced branching, up to 100(–200) mm high. Leaves tufted, oblanceolate to lanceolate, 40–80(–100) × 8–12(–18) mm; margin undulate, irregular shallowly dentate spinose, spines fine up to 2(3) mm long; hairs appressed to strigose with isolated sessile or subsessile glands; base attenuate; sessile to subsessile, if petiole present (up to 2 mm long). Inflorescences 25–60(–70) mm long, (8–) 10–12 mm in diameter. Bracts obovate to fan-shaped, 13–15(–20) mm long, base 5–8 mm long; middle and upper bracts ending in 5 primary spines; central primary spine always compound (with 2 or 3(4) pairs of marginal secondary spines), lateral spines with 2 basal secondary spines and 3(4) marginal secondary spines; spine tips often tinged maroon; primary spines usually recurved and secondary spines spreading in fruit; bract base hirsute to pubescent with deflexed to spreading short hairs, spines usually villose (long silky hairs interspersed with deflexed to spreading short hairs and short, subsessile glandular hairs, the latter <0.2 mm long). Bracteoles lanceolate, 7–9(–10) mm long, silky hairy. Calyx tips often tinged maroon; dorsal sepal ovate, apiculate to cuspidate, 10–12(–14) mm long, densely silky hairy, especially adaxially, 5–7-veined from base; ventral sepal ovate, 8–11 mm long, densely silky hairy, especially adaxially, 5–7-veined from base; lateral sepals 7–9 mm long, densely silky hairy. Flowers blue-purple with white throat, corolla 23–27 × 10–12 mm, tube 8–12 mm long, central lobe wider than long or equal, slightly constricted at base, truncate to emarginated. Stamens with anthers purple-black, 2 mm long; filaments 4–5 mm long, sparsely glandular, hairy towards base. Style with patch of glandular hairs at base. Capsules ovate in face view, flattened, glabrous, shiny, 6–7 × 3–4 mm, 2-seeded. Seeds 4 × 3 mm, covered with long white hygroscopic hairs.

Etymology: —The specific epithet, dispermoides (the Latin meaning “resembling disperma”) refers to the fact that the taxon were hitherto misidentified as A. disperma as opposed to the probably more closely related A. hoffmannseggiana , due to the absence of long, viscid glandular hairs on the bracts.

Distribution, ecology and phenology: —Known from only five populations in the western Little Karoo between Wittepoort in the north to Warmwaterberg in the south ( Fig. 1 ), a range falling within the Little Karoo Centre of Endemism ( Van Wyk & Smith 2001). Acanthopsis dispermoides grows on mountain slopes and rocky ridges (between 370–600 m) in a region receiving an average of 200–300 mm of rain per year. It is often found in the transition zone between the Fynbos and Succulent Karoo Biomes ( Rutherford & Westfall 1994, Low & Rebelo 1996, Mucina & Rutherford 2006) on sandstone or shale. Vlok & Schutte-Vlok (2010) recorded that this Little Karoo species can be abundant in clayey soils in Gwarrieveld (Thicket Biome), Ranteveld and Apronveld (Succulent Karoo Biome). Flowering time: June–October.

Conservation status: — Acanthopsis dispermoides has a restricted range (Extent of Occurrence 716 km ²), and occurs in an area that is severely overgrazed in places. It is however locally abundant, resilient to disturbance and appears to thrive under conditions of overgrazing, and is therefore unlikely to be threatened (J. Vlok, pers. com. 2015), and classified as Least Concern ( IUCN 2001) (L. von Staden, pers. com. 2015).

Notes: —Based on the distribution and the absence of long, viscid glandular hairs on the bracts, Viviers, Vlok & Bond 272 (PRE!) from Anysberg Mountain, is included in Acanthopsis dispermoides although the leaf indumentum includes spreading glandular hairs. Further fieldwork is needed to clarify the relationships between the two Western Cape species ( A. dispermoides and A. hoffmannseggiana ) and to determine the full distribution range and the abundance of Acanthopsis dispermoides . As more taxonomic evidence becomes available in future, it is quite possible that A. dispermoides would rather be regarded as an infraspecific taxon within A. hoffmannseggiana (see Notes under A. hoffmannseggiana ). For the moment, however, A. dispermoides is recognized at species level to highlight its morphological distinctness (mainly in bract and leaf indumentum and inflorescence diameter), and its geographical confinement to the Little Karoo, the most southerly distribution for a member of the genus.

Additional specimens examined: — SOUTH AFRICA. Western Cape: Wittepoort, (3320 BD), 23 September 1941, Barker 1507 ( NBG!) ; District Ladismith: Touwsberg; NW side of Touwsberg; Foothills of farm Kleinfontein 123, S33°32’31.5”, E20°55’36”, 450 m, (3320 DB), 6 October 1993, Bredenkamp 830 ( PRE!) ; Touwsberg; Farm Kleinfontein NW side of mountain, (3320 DB), 6 October 1993, Smook 8679 ( PRE!) ; Warmwaterberg, (3320 DD), 11 July 1945, Compton 20531 ( NBG!) ; Swellendam District. Warmwaterberg , at back of reception, along hiking trail, 510 m, (3320 DD), 16 August 2013, Steyn 1912 ( PRE!) ; Swellendam Div.; Warmwaterberg; ridge above Warmwaterberg hotel 18 mi. from Barrydale on rd. to Ladismith , 3000 ft, (3320 DD), 21 June 1963, Taylor 4874 ( PRE!, NBG!) ; Klein Karoo. Pad na Kromkloof by Droogedam , 370 m, (3321 CA), 16 June 1993, Bohnen 9352 ( NBG!) .

Without precise locality: Fourie STE31220 (NBG!).

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 10. Acanthopsis dispermoides: morphology. A & B. Habit. C & D. Leaf indumentum. E–G. Bract. H. Calyx. I. Flower (corolla lobes blue-purple; throat white). J. Glandular hairs at base of style. K. Capsule. L. Seed. Vouchers: C, E, G–J = Steyn 1912 (PRE), D, F, K, L = Boucher PRE 40576 (PRE).