Solanum ratale D. McClelland, 2020

McClelland, Donald H. R., Nee, Michael & Knapp, Sandra, 2020, New names and status for Pacific spiny species of Solanum (Solanaceae, subgenus Leptostemonum Bitter; the Leptostemonum Clade), PhytoKeys 145, pp. 1-36 : 1

Solanum ratale D. McClelland sp. nov. Figure 10

Diagnosis.

Like Solanum pseudopedunculatum D.McClelland but differing in shorter stature, densely glandular new growth, stellate trichomes with elongate midpoints that sometimes lack rays, smaller flowers and smaller, few-seeded fruits.

Type.

Fiji. Viti Levu: Mba, (Tholo North), Western division, village of Nadarivatu, Fish Hatchery 2600 ft, 9 Feb 1941 (fl, fr), O. Degener 14324 (holotype: A; isotypes: K [K000922635, K001155453], UC [acc. #1016245], US [acc. #1943693, barcode 02838817])

Description.

Shrub or small tree 0.5-1.5 m, the internodes to 3.4 cm long, unarmed or densely armed. Stems densely pubescent with yellow-ferruginous, sessile or short-stalked porrect-stellate trichomes, the stalks of various lengths to 0.2 mm long, somewhat bulbous, the rays 6-8 or absent, 0.15-0.25 mm long, the midpoint to 1.2 mm long, the prickles, if present, 4-6 mm long, dense, straight and somewhat retrorse (downward pointing), yellow or straw-colored; new growth densely to sparsely pubescent with sessile and short-stalked porrect-stellate trichomes and densely pubescent with minute glandular papillae ca. 0.04 mm long; bark of older stems reddish brown. Sympodial units difoliate, the leaves geminate, members of a pair similar in size and shape. Leaves simple; blades 4.3-10.4 cm long, 1.3-2.6 cm wide, 2.8-5.2 times as long as wide, narrowly lanceolate to narrowly elliptic, chartaceous to subcoriaceous, concolorous, armed or unarmed; adaxial surfaces moderately to sparsely pubescent with sessile and very short-stalked porrect-stellate trichomes and in some individuals with scattered prickles 3-4 mm long, along the veins, the stellate trichomes with the stalks to 0.6 mm long, the rays 4-8 or absent and the trichomes appearing simple, 0.2-0.3 mm long, the midpoint 1-2 mm long, sometimes gland-tipped; abaxial surfaces densely pubescent with sessile and stalked porrect-stellate trichomes and sometimes with prickles along the veins, the stellate trichomes with bulbous stalks to 0.1 mm long, the rays 6-8 or absent and the trichomes appearing simple, 0.25-0.4 mm long, the midpoint 1-2 mm long, much longer than the rays, the prickles if present 2-4 mm long, on the principal veins only, not on the midrib; principal veins 5-7 pairs, the midrib raised abaxially, raised adaxially, the lateral veins weakly brochidodromous, raised abaxially, raised adaxially, if the rest of the plant prickly then the veins with scattered, straw-colored prickles; base cuneate or rounded, equilateral or oblique; margins entire; apex acuminate; petiole 0.4-1.3 cm long, 0.6-1.0 mm in diameter, moderately to densely stellate-pubescent and sometimes with a few straight prickles like the leaf surfaces and stems, channeled above. Inflorescence to 1.8 cm long, appearing lateral, extra-axillary, emerging from the middle 1/3 of the internode, usually unbranched, occasionally forked, with (1-)4-13 flowers, moderately to densely pubescent with sessile and stalked porrect-stellate trichomes like those of the stems, in prickly individuals with 1-3 prickles; peduncle to 0.9 cm long, to 0.6 mm in diameter, pubescent and prickly like the stems; pedicels 0.6-0.8 cm long, ca. 0.3 mm in diameter at the base, ca. 0.6 mm in diameter below the calyx, bent to approximately 90° below the calyx, gradually increasing in diameter in the distal ca. 1/3, moderately to densely pubescent, articulated at the base; pedicel scars congested to spaced 2.2 mm apart, rigid, in two rows. Buds globose, the calyx moderately stellate-pubescent, the corolla densely stellate-pubescent where exposed abaxially, strongly exserted from the calyx before anthesis. Flowers 5-merous, all perfect. Calyx 1.5-2.3 mm long, appearing nearly truncate with caudate to subulate lobe tips, the tube 0.6-1.1 mm long, the lobe tips 0.9-1.3 mm long, the sinuses opaque when dry, not splitting or splitting in the sinuses during fruit development and then the lobes deltate, moderately pubescent abaxially, glabrous adaxially. Corolla ca. 0.5 cm in diameter, stellate, white, the interpetalar tissue well-developed, glabrous, the lobes 3.2-3.8 mm long, 1.9-2.2 mm wide, oblong, spreading at anthesis, moderately pubescent abaxially along the midvein, glabrous adaxially. Stamens equal; filament tube minute; free portion of the filaments ca. 0.5 mm long, glabrous; anthers ca. 1.3 mm long, 0.6 mm wide, oblong, somewhat incurved, apparently yellow, spreading, poricidal at the tips, the pores directed distally, extending around the edge of the apex. Ovary ca. 0.8 mm in diameter, globose, with a few simple glandular hairs at the apex; style ca. 2.8 mm long, ca. 0.3 mm in diameter, exserted from the anther cone, cylindrical, straight, glabrous; stigma ca. 0.5 mm in diameter, capitate, the surface minutely papillate. Fruit a globose, apparently juicy berry, 0.5-0.7 cm in diameter, black or deep purple when mature, glabrous, the pericarp thin, glossy, opaque; fruiting calyx not markedly accrescent, the lobes 2-3(-4) mm long, 1.3-1.6 mm wide, sparsely to moderately pubescent, appressed or somewhat reflexed; fruiting pedicels 0.8-1.5 cm long, ca. 0.5 mm in diameter at the base, 1.4-2.0 mm in diameter below the calyx, straight, gradually increasing in diameter in the distal ca. 2/3, sparsely to moderately pubescent,. Seeds 4-12 per berry, 2.3-2.5 mm long, 1.5-1.9 mm wide, flattened-reniform, yellow-tan when dry, the surface with the central area nearly smooth, the margins minutely and quite deeply pitted (alveolate), the walls of the testal cells straight. Chromosome number not known.

Distribution and ecology

(Figure 9 ). Solanum ratale is endemic to Fiji on the islands of Viti Levu and Vanua Levu. It is known from elevation of 200 to 800 m but may grow at lower elevation near Suva (but see below). The habitat has been recorded as logged-off forest (Degener 14324) or dense forest along streams (Smith 5370).

Phenology.

Known to flower and fruit February, May, and June.

Etymology.

The specific epithet which means "pertaining to rafts" references a note on Horne 679 indicating that the light wood was used for making rafts. Another specimen bearing Horne’s collection number of 679 (K000687673, Trichospermum calyculatum (Seem.) Burret of the Tiliaceae ) has a label "on waste land between Suva and the town of Koluba, Viti Levu, June 1878" but makes no mention of uses. This suggests a possible label mix-up, with the original label of Horne 679 being affixed to the duplicate of Horne 678; Trichospermum is a small tree with light wood, more likely to be used for making rafts and growing at lower elevations. Horne (1881), however, lists " Solanum sp. nov." as both his 678 and 679, so it appears he used the number 679 twice.

Preliminary conservation assessment

( IUCN 2019). EOO = 862 km2 [EN -Endangered]; AOO = 16 km2 [EN -Endangered]. Solanum ratale is known from only a few locations in forest, and no recent collections. We therefore assess it as EN (B1,2a,b), based on its relatively restricted distribution and the threats to forest habitat in island archipelagoes.

Discussion.

Very little is known about S. ratale due to the few collections in herbaria. It is most similar to S. pseudopedunculatum but can be distinguished by its shorter habit, occasionally prickly individuals, shorter pedicels, and smaller corolla, anthers, and fruit.

Solanum ratale is polymorphic for presence of prickles on all parts, as is found in many other spiny solanums, both in the Old and New World (e.g., S. elaeagnifolium Cav., see Knapp et al. 2017; S. setaceum Dammer and S. schumannianum Dammer, see Vorontsova and Knapp 2016). The collection Smith 5370 from Viti Levu is densely prickly, but otherwise conforms exactly to the other collections of S. ratale . This collection has been identified in herbaria as S. retrorsum Elmer, a Philippine species with a similar polymorphism in the possession of retrorse prickles, but differing in its plurifoliate sympodial units, larger trichomes with midpoints equal to the rays, and bright red berry.

Additional specimens examined.

Fiji. Vanua Levu: Mt. Labasa, 15 Jul 1883, Greenwood 619 (K); Rabi [Rambi] Island, May 1878 (fl, fr), Horne 678 (K). Viti Levu: Central Division, near Lutu, May 1878 (fl, fr), Horne 595 (GH, K); near Suva, Jun 1878 (fl, fr) Horne 679 [a] (GH, K); Mba (formerly Tholo North), valley of Nggaliwana Creek, N of sawmill at Navai, 725-850 m, 21 Jul 1947, Smith 5370 (A, US).

Figures

Figure 9. Distribution of Solanum pseudopedunculatum and S. ratale.

Figure 10. Solanum ratale D. McClelland (isotype Degener 14324, US [acc. 1943693, barcode 02838817]).