Solanum vagum Nees, Trans. Linn. Soc. London 17(1): 48 1834.

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

46. Solanum vagum Nees, Trans. Linn. Soc. London 17(1): 48 1834.

Fig. 76

Type.

India. Sin. loc., "S. corymbosum Pers.?, hb. Wight", Herb. Wight s.n. (Wallich cat. 2624b) (lectotype, designated here: GZU [GZU000255872]; isolectotypes: K [K001152841], K-W [K001116639]).

Description.

Erect shrubs 0.5-2.5 m tall, unarmed. Stems erect, terete, sparsely to moderately stellate-pubescent, soon glabrescent; pubescence of sessile to short-stalked porrect-stellate to somewhat multangulate trichomes, the stalks 0.1-0.2 mm long, the rays 4-12, 0.1-0.2 mm long, the midpoints shorter than or as long as the rays; new growth densely stellate-pubescent, the trichomes porrect-stellate, sessile or short-stalked, the stalks 0.1-0.2 mm long, the rays 6-8, 0.2-0.5 mm long, the midpoints equal to the rays; bark of older stems glabrescent, usually with only a few scattered stellate trichomes, greyish brown and somewhat shiny. Sympodial units plurifoliate, the leaves not geminate. Leaves simple, entire, the blades 5-15 cm long, 1.5-7 cm wide, lanceolate to narrowly elliptic to elliptic, membranous, discolorous; adaxial surface drying dark, glabrous or with a few scattered sessile porrect-stellate trichomes on the veins and lamina, the trichomes more delicate than those of the abaxial surfaces, with 4-8 rays 0.1-0.2 mm long and midpoints equal to the rays; abaxial surface paler, almost glabrous to moderately pubescent, the trichomes sessile or very short-stalked, the rays 4-8, 0.3-0.5 mm long, the midpoints equal to the rays; major veins 6-8 pairs, prominent and drying yellowish or darker than the lamina abaxially; base acute, somewhat oblique, but not markedly so; margins entire or slightly sinuate and irregularly lobed; apex acute to somewhat acuminate; petiole 2-6 cm long, 1/2 or more of the leaf blade length, glabrous to sparsely stellate-pubescent with porrect-stellate stellate trichomes like the stems. Inflorescences 3-8 cm long, apparently terminal or lateral, usually unbranched but occasional forked, with 4-10 flowers, 1-2 flowers open at any one time, glabrous to very sparsely pubescent with sessile porrect-stellate trichomes like those of the stems; peduncle 1-3 cm long; pedicels 1-1.2 cm long, 1-1.2 mm in diameter at the base, 1.5-1.8 mm in diameter at the apex, erect at anthesis, glabrous or sparsely stellate-pubescent like the inflorescence axes, articulated at the base or just above and leaving a minute peg on the inflorescence axis; pedicel scars spaced 1-3 mm apart. Buds ovoid, not markedly tapering, densely stellate-pubescent, strongly exerted from the calyx tube before anthesis, but the calyx acumens nearly to the tips of the buds. Flowers 5-merous, apparently all perfect. Calyx with the tube 1.5-2 mm long, conical, the lobes 1-2 mm long, 1-1.2 mm wide, narrowly deltate with a long subulate acumen to 2.5 mm long, glabrous or very sparsely pubescent abaxially with sessile porrect-stellate trichomes like those of the pedicels. Corolla 2-3 cm in diameter, white, stellate, lobed nearly to the base, the lobes 8-10 mm long, 2.5-3 mm wide, narrowly deltate, spreading at anthesis, glabrous adaxially, moderately pubescent abaxially with sessile stellate porrect trichomes, the rays 3-10, ca. 0.1 mm long, the midpoints equal to the rays, the tips somewhat cucullate. Stamens equal in bud, unequal at anthesis, with 4 short and one long and curved; long anther 7-9 mm long and strongly curved upwards, 1-1.5 mm wide, the short anthers 3-6 mm long, 1-1.5 mm wide, elliptic but the longer one somewhat tapering, all yellow, glabrous, poricidal at the tips, the pores directed distally and not elongating with age; filament tube minute, glabrous; free portion of all filaments ca. 0.5 mm long, glabrous; Ovary conical, glabrous or with a few porrect-stellate trichomes at the apex; style 9-11 mm long, slender, strongly curved in same direction as the long anther, glabrous or with a few porrect-stellate trichomes at the very base; stigma capitate, minutely papillate. Fruit a globose berry, 2-4 per infructescence, 0.8-1 cm in diameter, red at maturity, the pericarp thin and shiny, glabrous; fruiting pedicels 1.5-1.8 cm long, ca. 1 mm in diameter at the base, 2-2.5 mm in diameter at the apex, woody and erect; fruiting calyx lobes not markedly accrescent, splitting to the base and expanding to 4-6 mm long including the acumen which often breaks off in dry specimens. Seeds 10-20 per berry, 4-4.5 mm long, 3-4 mm wide, flattened-reniform, pale tan, the surfaces smooth in the seed centre, minutely pitted on the thickened margins, the testal cells somewhat sinuate in outline. Chromosome number; n = 12 ( Madhavadian 1968).

Distribution

(Fig. 77 ). Solanum vagum occurs in southern India (states of Kerala and Tamil Nadu) and in Sri Lanka.

Ecology and habitat.

Solanum vagum grows in dry open woodland, degraded vegetation, grasslands and open areas; occurring from sea level to 750 m elevation.

Common names and uses.

None recorded.

Preliminary conservation status

( IUCN 2019). Least Concern (LC). EOO (75,338 km2, LC); AOO (76 km2, EN). Solanum vagum is found both in southern India and Sri Lanka, and where it occurs it is a plant of open, disturbed areas, suggesting that it is not of immediate conservation concern.

Discussion.

Solanum vagum is morphologically similar and probably closely related to S. pubescens , sharing with that species zygomorphic flowers at anthesis, heteromorphic anthers and shiny berries on erect or slightly pendulous pedicels. Hepper (1987) treated material of S. vagum from Sri Lanka as S. pubescens in the "Revised Handbook to the Flora of Ceylon". It differs from S. pubescens in its complete lack of glandular pubescence, its narrowly elliptic leaves with attenuate bases and slightly larger, white (rather than violet) flowers. The pubescence of adaxial leaf surfaces of S. vagum is of very sparse sessile stellate trichomes with midpoints usually equal to the rays, and the lamina is clearly visible, while in S. pubescens the lamina of young leaves is obscured by the dense covering of glandular stellate to multangulate stalked trichomes with elongate midpoints. The two species apparently co-occur in southern India, while all specimens we have seen identified as S. pubescens from Sri Lanka are referable to S. vagum .

The long anther in the flowers of S. vagum appears to expand after anthesis; specimens with buds or very young flowers have the anthers all of equal size, while older flowers have one anther markedly longer than the rest. Post-anthesis anther expansion occurs in the unrelated S. turneroides Chodat (Brevantherum clade, see Stern et al. 2013) of southern South America. Buds of S. pubescens and the African species S. somalense Franch., which greatly resemble those of S. vagum , also have the anthers of more or less equal length and buds that are not markedly curved.

Solanum vagum is probably a member of the Giganteum clade (sensu Vorontsova et al. 2013; Aubriot et al. 2016a) based on similarity with S. pubescens and the African/Middle Eastern species S. somalense . These taxa can be distinguished from S. giganteum , the only other member of the group occurring in tropical Asia, by their zygomorphic flowers and calyx lobes with long subulate tips that are especially visible in bud.

The species has been indicated as endemic to the southern part of the Western Ghats biodiversity hotspot (https://indiabiodiversity.org/biodiv/species/show/264048) but also occurs in Sri Lanka.

Nees van Esenbeck (1834) validated the herbarium name previously listed as Wallich cat. 2624 citing two collections; " Solanum vagum . Herb. Heyn., Wall. l.c." (Wallich cat. 2624a) and " Solanum corymbosum? Herb. Wight" (Wallich cat. 2624b). We have selected the specimen at GZU that comes from Nees van Esenbeck’s own herbarium ( Stafleu and Cowan 1981) as the lectotype for S. vagum because it is clear that it was used by Nees, comes from one of the original collections in the Wallich herbarium and has both mature flowers and fruits. This collection from the Wight herbarium (Wallich cat. 2624b) also has more widely distributed duplicates than the other syntype from the Heyne herbarium (Wallich cat. 2624a). Although a specimen in BM (BM000900081) is labelled "Wall. cat. 2624b" it is also labelled as being from "herb. Heyne" and so is here treated as a syntype, not as an isolectotype.

Specimens examined.

See Suppl. materials 1-3.

Figures

Figure 76. Solanum vagum B. Heyne ex Nees A herbarium specimen collected in India in 1818 (Herb. Wight s. n. (Wallich cat. 2624 A), K 001116638) B habit (field photograph, unvouchered, India) C detail view of an infructescence (field photograph, unvouchered, India). Photograph credits: A © copyright of the Board of Trustees of the Royal Botanic Gardens, Kew B, C R. Vellingiri.

Figure 77. Distribution of S. vagum.