Solanum volubile
Citation:
Fl. Ind. Occ. 1: 458. 1797.
Type:
"West Indies", O. Swartz s.n. (lectotype, propsoed in Stern thesis: BM! [BM000815975]; possible isolectotypes: BM! [BM000886692], S).
Written by:
Stephen Stern
Habit:
Scandent shrub to woody vine 1-4 m. Stems moderately to densely armed with recurved, tan to orange roselike prickles, these 2-10 mm long, the base 1-7 x 0.5-1.5 mm, moderately pubescent with tan to rusty, porrect-stellate hairs, the stalks 0.5-3 mm, multiseriate, the rays 3-8, 0.5-1 mm, unicellular to multicellular, the midpoints nearly absent.
Sympodial structure:
Sympodial units difoliate, the leaves usually geminate, those of a pair often unequal.
Leaves:
Leaves simple, the blades 4-15 x 1-7 cm, ovate, leaves chartaceous, slightly discolorous, dark green adaxially, green to whitish green abaxially, the adaxial surface sparsely to moderately pubescent with stellate hairs like those of the stem but with the stalks to 0.5 mm and the midpoints to 0.5 mm (2-3 mm in some specimens from Trinidad), the abaxial surface moderately pubescent with stellate hairs like those of the stem; major veins 4-7 on either side of the midvein, the secondary veins obscure, the midrib abaxially with a few to many recurved prickles like those of the stem; base acute, often asymmetrical; margin with 2-4 obtuse lobes per side, the sinuses cut less than ¼ of the way to the midvein; apex acute; petioles 0.5-2.5 cm, moderately pubescent with hairs like those of the stem, moderately armed with prickles like those of the stem.
Inflorescences:
Inflorescences 2-6 cm, extra-axillary, unbranched, with 5-15 flowers, the plants andromonoecious, with male flowers on young plants and hermaphroditic flowers on older plants, the axes moderately to densely pubescent with hairs like those of the stem, unarmed; peduncle 0.5-1.5 cm; rachis 1.5-4.5 cm; pedicels 5-10 mm in flower, 10-20 mm in fruit, filiform, contiguous throughout, spaced 1-3 mm apart.
Flowers:
Flowers heteromorphic, hermaphroditic (long-styled) and staminate (short-styled) and the plants andromonoecious, 5-merous. Calyx 3-5 mm long, the tube 1-2 mm, the lobes 1-2 x 0.5-1 mm, triangular with acute apices, often recurved, moderately pubescent with hairs like those of the stem, occasionally with prickles 1-2 mm in length, straight to recurved; fruiting calyx 3-6 mm, not accrescent in fruit. Corolla 2-3 cm in diameter, chartaceous, white to cream with occasional purple lines, stellate, lobed nearly to the base, the lobes 10-15 mm x 1.5-3.5, narrowly triangular, slightly reflexed at anthesis, densely pubescent abaxially with stellate hairs like those of the stem but with 5-8 rays, these appearing partially proximally fused, adaxial surface glabrous. Stamens 10-13 mm; filaments 1-2 mm long, glabrous to moderately pubescent; anthers 8-12 x 1-2 mm, attentuate, tapering, connivent in bud, connivent to spreading in flower, yellow, the base cordate, the apex obtuse, the pores apical, directed slightly introrsely. Ovary moderately pubescent with white hairs like those of the stem; style in functionally male flowers 2-3 x 0.5-1.5 mm, style in hermaphroditic flowers 10-13 x 0.5-1 mm, exserted beyond the stamens, cylindrical, white, sparsely pubescent; stigma to 1 mm wide, cylindrical, green.
Fruits:
Fruit a leathery berry, 10-20 mm in diameter, globose, green when immature, orange when mature, glabrous to very sparsely pubescent.
Seeds:
Seeds 20-30 per fruit, reniform, brown, 2-2.5 x 1.5-2 mm, flattened, the surface netlike with many pits separated by small raised ridges.
Chromosome number:
Not known
Distribution:
Solanum volubile is a weedy species of forest edges, light gaps, and roadsides from Veracruz, Mexico through Central America and the northern coast of South America in Colombia, Venezuela, Guyana, and French Guiana and Trinidad and Tobago, commonly at sea level to 500m (1600 m).
Phylogeny:
Solanum volubile is a member of the Micracantha clade (section Micracantha) of the spiny solanums (Leptostemonum; Stern et al. 2011).
References:
Stern, S., M.F. Agra, & L. Bohs. 2011. Molecular delimitation of clades within new world species of the “spiny solanums” (Solanum subgenus Leptostemonum). Taxon.
The morphological characteristics of S. volubile are similar to S. aturense with which it is sympatric in much of its range. There is much morphological overlap between these species and viewing an individual specimen without additional material for comparison makes identification difficult. In general, S. volubile is characterized by leaves that are chartaceous, often lobed and lacking a revolute margin, and only sparsely or moderately pubescent abaxially, whereas leaves of S. aturense are thick and somewhat coriacsous, not lobed and frequently have a revolute margin, and are often densely pubescent abaxially. Additionally, S. volubile has smaller flowers (2-3 cm in diameter versus 3-4 cm in S. aturense), smaller fruits (1-2 cm versus 1.5-3.5 in S. aturense) and smaller seeds (2-2.5 x 1.5-2 mm versus 3-3.5 x 2-2.5 mm in S. aturense). Due to their similar morphologies, it is unsurprising that S. volubile is strongly supported (100% BS, 1.0 PP) as sister to S. aturense in phylogenetic results (Stern and Bohs in prep).
We have selected a BM sheet as the lectotype of S. volubile as this is the only known specimen, although there is possibly a collection at S where Swartz was based. The description of S. purulense did not specify a holotype so we have lectotypified the collection at US, as it is the only known collection and is excellent material. The name S. donnell-smithii is a nomen nudum and appears to simply be a copy of his collection labels.
Much material of S. volubile in herbaria has been annotated as S. adhaerens, a synonym of this species.
The etymology of S. volubile is unclear; it is possible that it is from the Latin “volubil-” meaning “turning” referring to the twining, scandent growth form.