Nemesia arenifera Bester & H.M.Steyn, 2013

Bester, Stoffel P. & Steyn, Hester M., 2013, Nemesia arenifera (Scrophulariaceae), a new species from the Sandveld, Northern Cape Province, South Africa, and the lectotypification of N. viscosa, Phytotaxa 126 (1), pp. 49-54 : 50-53

Nemesia arenifera Bester & H.M.Steyn , spec. nov. ( Fig. 1 )

Diagnosis:— Nemesia areniferae sp. nov. N. rupicolae Hilliard in Hilliard and Burtt (1986: 396) quoad labium inferum corollae in linea cum calcari portatum plusminusque ad pedicellum parallelum similis, sed floribus multo minoribus, luteis (non plerumque albis vel dilute roseis, dilute caeruleis vel malvinis), foliis anguste lanceolatis ad ellipticis vel oblongis, minute dentatis (non late ovatis, non manifeste dentatis). Ceterum, hae species bene distinctae distributione geographica: species nova littora incolens ad oras occidentales provinciae Northern Cape sed N. rupicola species montana rupes incolens in regione orientali Africae australis.

Type: — SOUTH AFRICA. Northern Cape: Namaqualand District. Namaqua National Park , ca. 24.6 km NE of Koingnaas, 203 m, 30°01'13.2"S 17°25'35.1"E (3017 AB), 11 August 2011, M. Koekemoer 4202 (holotype PRE!; isotypes BOL!, K!, KMG!, NBG!)

Description: —(All measurements are based on herbarium specimens). Annual, erect herb 40–300 mm high; stems simple or branching from base, lateral stems up to 100 mm long, square in cross-section, ridged because of decurrent leaf bases, often dark reddish, leafy. All parts of plant glandular pilose, except most of corolla, with spaced, transparent to whitish hairs, mostly ± patent, terete with exudate a little broader than hair itself. Leaves simple, opposite to subopposite or sometimes alternate near stem apex, sessile to shortly petiolate, decurrent on stem; leaves on short, lateral shoots tufted and appear congested and clumped together; lamina narrowly lanceolate, elliptical or oblong, often longer than internodes, 11–40 × 2–7 mm; base attenuate; apex mostly obtuse sometimes sub-obtuse, rarely acute; margins entire to sparingly dentate with 2–7 pairs of very small, narrowly deltoid teeth, usually in upper half. Bracts alternate, sessile, leaf-like, becoming smaller upwards. Pedicels up to 9 mm long, elongating and recurved or variously contorted when fruit matures. Calyx 5-lobed, spreading, 1.5–6.3 × 0.4–1.8 mm, weakly bilabiate with two lobes somewhat broader than the other three, oblanceolate to narrowly obovate or oblong; apex mostly obtuse some sub-obtuse, glandular pilose. Flowers axillary or in lax racemes up to 80 mm long. Corolla bilabiate, 3.8–8.3 × 1.9–6.5 mm, pale to bright yellow; upper lip 4-lobed, 3.9–5.1 × 2.4–3.8 mm, base a stronger yellow with faint magenta to maroon venation forming vertical streaks, continuing down into the tube, base ± perpendicular to margins, apex rounded to emarginate; two inner lobes slightly smaller than other two, semi-erect, oblong to ovate; two outer lobes oblong to elliptic, slightly spreading; lower lip with one lobe, widely obovate and emarginate or obcordate, 2.3–2.6 × 1.0– 3.3 mm, basal portion inflated into convex projecting palate; palate bright yellow, longitudinally grooved, glabrous; boss glabrous or slightly papillate, a stronger yellow than main part of corolla; tube> 0.5 mm long, pale yellow; hypocotyle (floor of corolla tube) 3.0– 3.3 mm long, sides invaginated to form a narrow channel, base of tube drawn out into a conical, backward-projecting spur, 1.8–4.4 × 0.2–1.4 mm, glabrous, bright yellow, held ± parallel to the pedicel. Stamens 4, lying in a shallow depression in upper inside surface of corolla tube; filaments of anticous pair 1.1–1.8 mm long, sigmoid, ± straight in middle; posticous filaments 0.6–0.7 mm long, ± straight except at base; anthers 0.5–0.6 mm long, each pair strongly coherent. Ovary ovoid, 2.0–2.5 × 1.0– 1.5 mm, glabrous, laterally compressed; style stout, straight, 0.4–0.5 × 0.3–0.4 mm, compressed contrary to the ovary, apex wider than base, lying between anther pairs; stigma simple, oval or slightly triangular in cross-section, stigmatic surface finely papillate, darker than style. Capsules ± oblong-ovoid in outline, 4.5–11.0 × 4.0–5.0 mm, laterally compressed contrary to septum, apex emarginate to bilobed, lobes rounded to acute with very steep angle between them, apical incision 1.0– 2.3 mm deep. Seeds widely ovate, 1.2 × 0.3–1.7 mm, light brown, verruculate, winged; wing membranous and fluted. Flowering & fruiting: August–September.

Distinguishing characters: — Nemesia arenifera does not resemble any known Nemesia species from southern Africa. Diagnostic characters include the erect habit, small yellow flowers with the spur carried parallel to the pedicel and the viscid indumentum. It differs from N. viscosa in habit, leaf and floral characters ( Table 1). In N. arenifera and N. rupicola the lower lip of the flower is in line with the spur and parallel to the pedicel, however, these species differ significantly from each other in habit, distribution, leaf and various floral characters ( Table 1).

Etymology: —The specific epithet, arenifera , refers to the preference of this species for deep, loose, sandy soils. The glands that cover the whole plant surface exude a sticky substance and sand adheres to this so the plant is literally “covered in sand”.

Distribution and habitat: — Nemesia arenifera seems to be restricted to the arid coastal dune systems from Alexander Bay in the north to Groen River Mouth in the south ( Fig. 2 ) at an elevation of less than 300 m. Current distribution records suggest it to be a Northern Cape, coastal endemic.

It occurs in deep, loose aeolian sand, ranging from white through yellow to red. This species is known only from the Namaqualand Sandveld Bioregion (vegetation types SKs1, SKs7, SKs8) and Sand Fynbos Bioregion (vegetation type FFd1) within the Succulent Karoo and Fynbos Biomes respectively ( Mucina & Rutherford 2006). Winter rains are predominant, falling mainly between May and August with an average of 50–114 mm per annum. Dense fog, especially in winter, contributes to the precipitation and frost is very rare.

Conservation status: — Nemesia arenifera currently has a threat status of LC (Least Concern) (L. von Staden pers. comm.). Although this species has a restricted range (extent of occurrence of 2 767 km ²), it is fairly common (known from more than 10 locations), and subpopulations can be large during years of above average rainfall. Some subpopulations near the coast may be declining due to habitat loss because of mining. However, only about 3% of this species’ range is currently transformed, and mining is unlikely to be a severe threat.

Additional specimens examined (paratypes): — SOUTH AFRICA. Northern Cape: Namaqualand, Alexander Bay, Visagiesfonteinkop at base of granite outcrop (2816DC), 26 August 1978, A. Le Roux & M. Ramsey 212 (PRE!); In arenosis prope Port Nolloth. In Namaland Minore, 50 ft, (2916BD), August 1883, H. Bolus in Herb. Normale Austro-Africanum 650 (PRE!); Namaqualand District, between Koingnaas and Kleinzee, on turn-off towards the coast where the new Nuclear Powerstation is planned, 56 m, 29°49'14"S 17°06'10"E (2917CC), 11 August 2007, S.P. Bester 7928 (PRE!); Namaqualand, Sandveld, Farm: Zonnekwa 326, plateau W of Sonnekwa homestead on a plateau dune (2917CC), 21 August 1993, A. le Roux 4524 (NBG, scan!); Namaqua National Park, Farm: Taaiboschvlakte 337, ± 13.4 km NNW of Riethuis homestead, 189 m, 29°59'56.4"S 17°23'22.9"E (2917CD), 15 August 2009, S.P. Bester 9488 (PRE!); Namaqua National Park. Farm: Taaibosch Vlakte 337, 22.6 km NW of Soebatsfontein and 25.5 km NNE of Koingnaas, 211 m, 29°59'29"S 17°24'31"E (2917CD), 13 August 2007, S.P. Bester 7968 (PRE!, KMG!, KSAN!, MO!); Namaqualand District, between Koingnaas and Kleinzee, 43 m, 30°06'54" S 17°12'56" E (3017AA), 10 August 2007, S.P. Bester 7879 (PRE!); Namaqualand National Park, Farm: Roodelaagte 476, ± 18.4 km NE of Hondeklip Bay, 131 m, 30°11'48.6"S 17°24'22.8"E (3017AB), 18 August 2009, S.P. Bester 9534 (PRE!); Namaqua National Park, Farm: 477, Jantjieskop portion, ± 15.6 km directly NE of Hondeklipbaai, 185 m, 30°14'25.0"S 17°24'38.0"E (3017AB), 19 August 2009, S.P. Bester 9544 (PRE!); 100 m from Koiingnaas-Hondeklip Bay main road at Swartlintjies River (3017AB), 27 August 1986, A. le Roux & J.W. Lloyd 359 (NBG, scan!); Namaqualand National Park, Farm 477, ± 400 m W of Taaiboschduin homestead and ± 15.8 km NE of Hondeklip Bay, 177 m, 30°15'32.7"S 17°25'40.2"E (3017AD), 17 August 2009, S.P. Bester 9508 (KSAN!, PRE!); Namaqua National Park, Farm: Avontuur 488, ± 10.2 km directly SE of Hondeklipbaai, 129 m, 30°21'19.9"S 17°22'24.5"E (3017AD), 19 August 2009, S.P. Bester 9571 (PRE!); Namaqua National Park, Farm: Kanoep 491, ± 23.8 km SE of Hondeklip Bay, 30°28'54.0"S 17°26'14.5"E, 47 m, (3017AD), 21 August 2009, S.P. Bester 9631 (NBG!, PRE!); Namaqua National Park. Farm: Diknek 486, 56m, 30°22'59"S 17°27'31"E (3017AD), 7 September 2010, S.P. Bester 10061 (PRE!); Namaqua National Park, Farm: Avontuur 488, S of Wallekraal-Hondeklipbaai road, 130 m, 30°21'16"S 17°22'20"E (3017AD), 11 August 2006, H.M. Steyn 967 (PRE!); Namaqua National Park, West Coast section, ca. 15 km North of Groenrivier, Kawass Annex area, 27 m, 30°44'12"S 17°31'35"E (3017DA), 19 August 2005, S.P. Bester 5950c (PRE!); Groen Rivier Mouth near lighthouse (3017DC), 25 August 2002, P. Goldblatt & L.J. Porter 12115 (NBG, scan!).

Figures

FIGURE 1.—Nemesia arenifera. A: habit. B: toothed leaf margin with glands. C–E: flower, C: front view at angle; D: side-view; E: viewed from below. F: mature capsule. G: seed. A–E: Steyn 967 (PRE); F & G: Bester 9508 (PRE). Scale bars: A, 10 mm; B, 0.35 mm; C, 1 mm; D & E, 1 mm (between D & E); F, 2 mm; G, 0.2 mm. Artist: G. Condy.

FIGURE 2.—Known distribution of Nemesia arenifera, based on specimens at PRE and NBG. Specimens collected through the National Herbarium Plant Collecting Programme (2005–2011), •; other collections, Θ.