Solanum wilkinsii Moore (1926: 95)

Bean, A. R., 2012, A taxonomic revision of the Solanum echinatum group (Solanaceae), Phytotaxa 57 (1), pp. 33-50 : 47-50

Solanum wilkinsii Moore (1926: 95) ( Fig. 5 ).

Type: — AUSTRALIA. Northern Territory: Groote Eylandt , March 1925, C.H. Wilkins 131 (holotype BM! [ BM000849515 ] ).

Prostrate or sprawling shrub 0.1–0.8 m high. Adult branchlets yellow, brown or purplish; prickles 0–230 per decimetre, straight, acicular, 0.5–3 mm long, 6–9 times longer than wide, glabrous; stellate hairs very dense, 0.3–0.5 mm in diameter, the stalks 0–0.3 mm long, the central ray 0.8–1.2 times as long as laterals. Adult leaves simple, the blades narrowly ovate to ovate, 4.1–8.3 cm long, 1.9–3.3 cm wide, 2.2–3.5 times longer than broad. Upper surface green or grey-green, prickles absent; stellate hairs sparse to moderate density, spaced 0.2–0.4 mm apart, 0.3–0.4 mm across, the stalks 0–0.1 mm long, the central ray 0.8–1.2 times as long as laterals. Lower surface white or grey, prickles absent; stellate hairs very dense, spaced ca. 0.05 mm apart, 0.3–0.4 mm diameter, the stalks 0–0.1 mm long, the central ray 0.8–1.2 times as long as laterals; entire, the base cuneate or obtuse, the oblique part 0–10 mm long, obliqueness index 0–12 percent, the apex acute; petioles 0.9–3.0 cm long, 18–42 % length of lamina, prickles absent. Inflorescence 3–5-flowered, with common peduncle 8–23 mm long, rachis prickles present; pedicels at anthesis 4–9 mm long, prickles absent or present; calyx tube 2.5–3.5 mm long, the lobes deltate to attenuate, 2–6 mm long; calyx prickles absent or present at anthesis, 0–60 per flower, 0.5–5 mm long; calyx stellae very dense, yellow to brown, 0.3–0.45 mm across, the stalks 0–0.3 mm long, the central ray 0.8–1.2 times as long as laterals. Corolla purple, 12–16 mm long, the inner surface glabrous; anthers 4.1–5.1 mm long; free part of the filaments 2–2.8 mm long; style ca. 10 mm long, erect, protruding between anthers or strongly bent, eccentric, glabrous. Fruiting calyx almost closed at the apex rendering fruit almost invisible; stellate hairs all about the same size, the stalks 0–0.3 mm long, proto-prickles absent; prickles>100, 1.5–8 mm long, straight, with stellae attached near the base; pedicels 8–14 mm long. Mature fruits 1 or 2 per inflorescence, oblate, ca. 15 mm diameter.

Distribution and habitat: — Solanum wilkinsii is endemic to north-eastern Northern Territory, including several islands in the Gulf of Carpentaria ( Map 1 ). It grows on stabilised coastal dunes in “ Acacia scrub” or coastal vine forest, or on ridges with deep sandy soil.

Phenology: —Flowers and fruits have been recorded in March and April.

Specimens examined: — AUSTRALIA. Northern Territory: Blue Mud Bay, Morgan Island , 30 April 1993, I.D. Cowie 3981 & G. Leach (DNA, MEL); Bickerton Island, 29 April 1993, C.R. Dunlop 9305 & G.J. Leach (DNA); Winchelsea Island, 13 May 1993, J. Egan 2441 ( BRI, DNA); Wessel Islands , 16 October 1972, P.K. Latz 3488 ( BRI, DNA); Mouth of Angurugu River , Groote Eylandt, 9 March 1988, J. Russell-Smith 5161 & D. Lucas ( BRI, CANB, DNA); Little Lagoon, Groote Eylandt, 14 April 1948, R.L. Specht 239 ( BRI, CANB, MEL); Emenbinungwa, S of Dalimba Bay, Groote Eylandt , 17 March 1979, J. Waddy 744 ( CANB); Groote Eylandt , February 1925, C.H. Wilkins 82 ( BM).

Notes: —The prickles on the branchlets of S. wilkinsii are no more than 3 mm long, and on some specimens they are completely lacking. It is also characterised by the more erect habit (reportedly up to 0.8 m high), the moderate density of stellate hairs on the upper leaf surface and the very small stellate hairs (0.3–0.5 mm across) on all plant parts.

Its small stellate hairs distinguish it from S. echinatum and S. lucani ; while from S. lapidosum , S. medicagineum and S. rhaphiotes it is distinguished by its larger corolla, longer filaments and very short (sometimes absent) branchlet prickles. From S. fecundum , it differs by the more upright habit, the shorter prickles of the branchlets, the smaller stellate hairs of the lower leaf surface, the fewer flowers in the inflorescences, the longer calyx lobes, and the oblate fruits. Its preference for deep sandy soils near the ocean is also diagnostic.

The author of the name S. wilkinsii mentioned the collection number “131” of Wilkins, and it was the sole specimen cited. It may therefore be regarded as the holotype.

The specimen Latz 3488 (cited above) is only tentatively included here: it differs from all other collections by the broader leaves (ca. 1.5 times longer than wide) and the very dense stellate hairs on the upper leaf surface. In other vegetative characters, it appears to agree with S. wilkinsii , but it may represent an undescribed taxon.

Figures

MAP 1. Distribution of Solanum echinatum (circles); Solanum wilkinsii (triangles); Solanum medicagineum (stars).

FIGURE 5. Solanum wilkinsii. A. branchlet and leaves; B. a stellate hair from the branchlet; C. corolla and stamens; D. calyx and pedicel at anthesis; E. ovary and style; F. infructescence showing fruiting calyces; G. transverse view of dried fruit; H. polar view of dried fruit; I. a section of the fruiting calyx showing prickles and hairs. A–E from Dunlop 9305; F, I from Egan 2441; G–H from Egan 2770. Scale bar: A = 7.5 mm, B = 0.25 mm, C = 4 mm, D = 4 mm, E = 2 mm, F = 8 mm, G = 6 mm, H = 6 mm, I = 1.5 mm.