Solanum robinsonii Bonati, Bull. Soc. Bot. Geneve , ser . 2, 3: 311. 1914.

Aubriot, Xavier & Knapp, Sandra, 2022, A revision of the " spiny solanums " of Tropical Asia (Solanum, the Leptostemonum Clade, Solanaceae), PhytoKeys 198, pp. 1-270 : 1

38. Solanum robinsonii Bonati, Bull. Soc. Bot. Geneve, ser. 2, 3: 311. 1914.

Figs 2C , 65

Type.

Vietnam. Khánh Hòa: Nha-trang and vicinity, 11-26 Mar 1911, C.B. Robinson 1082 (lectotype, designated here: P [P00054128]; isolectotype: K [K000922030]) .

Description.

Erect shrub, up to 1 m tall, unarmed. Stems erect, terete, sparsely to moderately stellate-pubescent, glabrescent; pubescence of mixed sessile and short-stalked porrect-stellate trichomes, the stalks to 0.08 mm long, the rays 7-8, 0.1-0.2 mm long, the midpoints to 0.03 mm long with bulbous bases; new growth densely stellate-pubescent, light brownish green; bark of older stems brownish grey, glabrous. Sympodial units plurifoliate, the leaves not geminate. Leaves simple, entire, the blades 3-8 cm long, 1-3 cm wide, ca. 2-3 times longer than wide, elliptic to ovate, chartaceous, strongly discolorous; adaxial surface moderately stellate pubescent, the trichomes porrect-stellate, sessile and short-stalked, the stalks extremely short, the rays 6-8, 0.05-0.15 mm long, the midpoints to 0.08 mm long, with bulbous bases; abaxial surface densely stellate-pubescent with sessile and short-stalked porrect-stellate trichomes, the stalks if present to 0.5 mm, the rays 5-10, 0.2-0.5 mm long, the midpoints to 0.2 mm, stout with a bulbous base, the lamina completely obscured; major veins 4-9 pairs, markedly impressed above, drying light green; base cuneate; margins entire or somewhat undulate, never lobed; apex rounded to acute; petiole 0.5-1 cm long, 1/10-1/5 of the leaf blade length, densely stellate-pubescent with trichomes like those of the stems and leaves. Inflorescences 1-3 cm long, internodal and lateral, unbranched, with ca. 5-10 flowers, only a few flowers open at any one time, densely stellate pubescent with porrect-stellate trichomes like those of the stems; peduncle 0.4-2.5 cm long; pedicels 4-9 mm long, 0.7-1 mm in diameter at the base, 1.3-1.5 mm in diameter at the apex, erect to recurved, densely stellate-pubescent with porrect stellate-trichomes like those of the axes, articulated at the base; pedicel scars spaced 0.5-2 mm apart. Buds elongate-ovoid, pointed at the tip, the corolla ca. halfway exserted from the calyx before anthesis. Flowers 5-merous, apparently all perfect. Calyx with the tube 1.4-2 mm long, campanulate, the lobes 2-3 mm long, 0.6-0.8 mm wide, narrowly deltate and narrowing to an elongate acumen, the acumen 2/3-3/4 the total lobe length, densely stellate-pubescent with porrect stellate-trichomes like those of the pedicels. Corolla 1-2 cm in diameter, blue to purple, stellate, lobed ca. 1/2-2/3 of the way to the base, the lobes 4-5 mm long, 2-2.5 mm wide, deltate, spreading at anthesis, densely stellate-pubescent abaxially on parts exposed in bud. Stamens equal or very slightly unequal with 2 longer than the rest; anthers 5-6 mm long, 0.5-0.75 mm wide, if unequal then 2 ca. 0.1 mm longer than the rest, tapering, connivent, yellow, glabrous, poricidal at the tips, the pores not lengthening to slits with age; filament tube <0.5 mm long; free portion of the filaments 0.4-0.75 mm, glabrous. Ovary conical, with minute glandular hairs at the top; style 7.5-9 mm long, slender, curved at the apex, glabrous; stigma capitate, minutely papillate. Fruit a globose berry, 1-2 per infructescence, 0.7-1.2 cm in diameter, the pericarp smooth, red when mature, glabrous; fruiting pedicels 1.2-1.6 cm long, ca. 0.5 mm in diameter at the base, 1.5-1.8 mm in diameter at the apex, woody, erect to recurved; fruiting calyx lobes slightly expanding to 4-5 mm long, 1/2-2/3 the length of the mature fruit, narrowly deltate, appressed to the berry, ending with a long acumen. Seeds ca. 10-15 per berry, 3-4 mm long, 2.5-3 mm wide, flattened-reniform, dull yellow, the surface minutely pitted, the testal cells pentagonal in outline. Chromosome number: not known.

Distribution

(Fig. 66 ). Solanum robinsonii is endemic to Vietnam; the few known collections are restricted to Khánh Hòa and Ninh Thuân provinces of southeast Vietnam.

Ecology and habitat.

Solanum robinsonii grows on hillsides in deciduous forests, at ca. 200 m elevation.

Common names and uses.

None recorded.

Preliminary conservation status

( IUCN 2019). Endangered (EN [B1,2abii,iii]). EOO (610 km2, EN); AOO (20 km2, EN). Solanum robinsonii has a narrow distribution and grows in coastal forests that are subject to much anthropogenic disturbance. The species is of concern due to extreme habitat alteration ( Wikramanayake et al. 2002).

Discussion.

Solanum robinsonii is superficially similar to S. putii of Thailand and S. nienkui of Hainan Island, China. The three taxa share a spindly shrubby habit, long, thin anthers and small red berries. Solanum robinsonii can be distinguished from S. putii in its more narrowly elliptic leaves that are more strongly discolorous when dry, and from S. nienkui in its slightly larger corollas (to 2 cm in diameter versus to 1.3 cm in diameter) that are less deeply stellate, and in its longer style (7.5-9 mm long versus 5.5-6 mm long).

The strongly discolorous leaves of S. robinsonii are reminiscent to those of S. giganteum , but that species has highly branched inflorescences and stout, prickly stems. Specimens of S. robinsonii have been considered to look like S. elaeagnifolium (annotation by D.E. Symon on the isolectotype specimen at Kew); this is due to the bulbous bases of the midpoints that make the trichomes look slightly lepidote. Solanum elaeagnifolium , however, has true lepidote trichomes that are more shield-like in structure (see Knapp et al. 2017).

Hul and Dy Phon (2014) erroneously cited the specimen in P as the holotype of S. robinsonii . Although Bonati worked in Paris, he did not cite any herbarium in the protologue or in the introductory part of his treatment ( Bonati 1914), so lectotypification is necessary. We here select the Paris sheet (P00054128) annotated by Hul and Dy Phon as “holotype” as the lectotype for S. robinsonii .

Specimens examined.

See Suppl. materials 1-3.

Figures

Figure 2. Vegetative characters for tropical Asian spiny solanums A large and densely hairy repand leaf of S. lasiocarpum (Meeboonya et al. RM 287, Thailand) B small, pubescent, very shallowly lobed leaf of S. miyakojimense (field photograph, unvouchered, Taiwan) C entire, pubescent leaf of S. robinsonii (Nuraliev 3031, Vietnam) D glabrescent and deeply dissected leaf of S. virginianum (Sampath Kumar et al. 126968, India) E conical straight prickles on a pubescent young stem of S. hovei (field photograph, unvouchered, India) F strongly hooked prickles on a glabrous young stem and on the abaxial leaf surface of S. trilobatum (Meeboonya et al. RM 242, Thailand) G needle-like purple prickles on the adaxial leaf surface of S. cyanocarphium (field photograph, unvouchered, Vietnam) H pubescent young stem of S. barbisetum armed with prickles and bristles (Suksathan et al. PS 3832, Thailand). Photograph credits: A, B, D-F X. Aubriot C, G M. Nuraliev H D. Pedersen.

Figure 65. Solanum robinsonii Bonati A herbarium specimen (holotype) collected in Vietnam in 1911 (Robinson 1082, P 00054128) B habit (Nuraliev 3031, Vietnam) C detail of the abaxial surface of a leaf blade (Nuraliev 3031, Vietnam) D inflorescence and detail view of an open flower (Nuraliev 3031, Vietnam) E detail view of a fruit (Nuraliev 3031, Vietnam). Photograph credits: A CC-BY, Museum national d'Histoire naturelle, Paris B-E M. Nuraliev.

Figure 66. Distribution of S. robinsonii.