Solanum myriacanthum

Citation author:

Dunal

Citation:

Hist. Solan. 218, tab. 19. 1813.

Type:

Cultivated at Montpellier, of unknown origin, M. Dunal s.n. (Holotype: MPU).

Last edited by:

Nee, M.

Written by:

Nee, M.

Habit:

Erect shrubs 0.5-1.5 m tall, single-stemmed with relatively few ascending branches. Stems densely spreading glandular-pilose with simple hairs of various sizes up to 1.6 mm long; stem spines few to numerous, dimorphic, many straight slender acicular and spreading to slightly reflexed of various lengths up to 7 mm long, with a few minute gland-tipped hairs and at base a few simple 1–2-celled acute hairs up to 0.3 mm long, with fewer scattered stout recurved spines to 11 mm long with enlarged and compressed bases to 4 mm wide.

Sympodial structure:

Sympodial units 2-foliate, geminate or not.

Leaves:

Leaves simple, the blades 4–15 x 4–14cm, about as long as wide, often geminate, the larger blades 7–15 x 7–14 cm, suborbicular or broadly ovate, the smaller blades about half the size of the larger and differing only in size, thin-textured, adaxially densely glandular-pilose with simple hyaline hairs up to 2–4-celled and 0.8–1.6 mm long intermixed with shorter simple hairs, abaxially similarly densely glandular-pilose mixed with sessile 4–6-rayed stellae 0.5–0.9 mm wide, the midpoints ca. 0.6 mm long, the stellae often with auxiliary rays below the main plane, sparsely armed adaxially and abaxially on major veins with slender straight spreading acicular spines similar to the larger ones on the petiole and grading down to minute ones on the smaller veins; base truncate to subcordate; margin very shallowly lobed with 3–5 pairs of obtuse to acute lobes, the terminal 1/3 of the blade usually broadly triangular with undulate margins; apex acute; petioles of the major leaves 4–10 cm, abundantly pubescent with simple gland-tipped hairs and scattered acute simple hairs, with 3–18 straight acicular spines up to 1.6 cm long and 2 mm wide at the base, at least some spines much larger than the straight prickles of the stems.

Inflorescences:

Inflorescences 0–0.5 cm, extra-axillary, unbranched, with (1–) 2–4 (–5) flowers, the lowermost 1–2 (–4) fertile, the axes densely short-pilose with simple hairs 0.2 mm long and with scattered longer simple hyaline hairs to 0.8 mm long, with few slender spreading acicular prickles 0.8–2.5 mm long in flower and up to 5 mm long in fruit; peduncle generally absent; rachis 0–0.5 cm; pedicels 7–12 mm in flower, 12–20 mm in fruit, terete and scarcely enlarged at the apex, curved horizontally around the stem, nearly contiguous.

Flowers:

Flowers with the calyx 3.5–5.5 mm long, the tube 1–2 mm, the lobes 2.4–3.6 long, 1.5–2 mm at the base, triangular-lanceolate, acute at tips, with pubescence and spines similar to that of the pedicels but often with an admixture of longer simple hyaline hairs with up to 3 cells and 2.8 mm long; fruiting calyx accrescent, the lobes 7-10 x 4.5-5.5 mm at base, triangular, usually withered or fallen in fruit. Corolla 1.7–2.5 cm in diameter, 7–14 mm long, stellate, thin-textured, yellowish green in bud and early anthesis, becoming nearly white in late anthesis, the tube 0.7–1.2 mm, the lobes 8–10.5 x 3.4–4.5 mm, narrowly triangular, acute and curled at apices, pilose abaxially with 2–4-celled simple hyaline hairs 0.4–2 mm long, the shorter ones gland-tipped, glabrous adaxially. Stamens with filaments 0.6–1.5 mm long; anthers 6.2–8.1 x 1.2–2.3 mm, narrowly lanceolate, free, golden yellow, the pores small and directed distally. Ovary minutely glandular; style ca. 8 x 0.3–0.4 mm in fertile flowers, exceeding the anther column by ca. 1 mm, cylindrical, straight, glabrous; stigma capitate.

Fruits:

Fruits 2–3 cm in diameter, globose, light yellow at maturity, glabrous.

Seeds:

Seeds 200-310 per fruit (x = 260, n = 9), 2.7-3.1 mm in diameter, flattened-reniform, brownish tan when mature, the surface minutely pitted.

Chromosome number:

n = ploidy missing =12 voucher missing =

Distribution:

A weedy shrub of secondary vegetation, pastures, roadsides, cultivated land, thickets and edges of forest, in zone of subtropical dry forest, tropical evergreen forest, oak-pine forest or cloud forest, from Tamaulipas south through eastern Mexico to Guatemala, El Salvador, Honduras and northern Nicaragua; sporadic in western Cuba where apparently still present and Louisiana, where it has not persisted. From sea level to 1700 m elevation, rarely higher.

Phenology:

Commonly flowering in all months but December, January and February.

Phylogeny:

Solanum myriacanthum is one of a trio of very closely related species included in an unnamed series of sect. Acanthophora of subgen. Leptostemonum (Nee, 1999); the other two are S. viarum Dunal and S. aculeatissimum Jacq.; this series is a well-supported monophyletic group (Levin et al., 2005). A key to the three is provided by Nee (1991). Solanum myriacanthum belongs to the Leptostemonum clade of Solanum (Bohs, 2005). Within Leptostemonum, it belongs to the Acanthophora clade, a monophyletic group that includes most of the species traditionally recognized in Solanum section Acanthophora Dunal (the S. mammosum species group of Whalen, 1984; Levin et al., 2006).

Commentary:

Of the three species of sect. Acanthophora with which S. myriacanthum is sympatric, S. acerifolium and S. capsicoides can easily be differentiated by their winged seeds, and S. mammosum has larger blue flowers and larger seeds. Its relationship to the more widespread but not sympatric S. viarum and S. aculeatissimum are discussed under S. viarum.

The collections cited here are fairly uniform, but a few are uncomfortably close to S. viarum or S. aculeatissimum. At times the enlarged recurved spines are absent on herbarium specimens and the leaves are thinner and more sharply lobed. These collections could be taken for S. aculeatissimum but they more probably represent shade forms of S. myriacanthum. Two collections of from Guatemala (Williams et al. 40306, Harmon 2029) have puberulent ovaries and should thus key to S. viarum but in other respects they are typical of Central American S. myriacanthum. Since until the 1980's there were no other records of S. viarum from North America except as a waif in Massachussetts, for now I am considering these two collections as aberrant S. myriacanthum.

The pre-Columbian range of S. myriacanthum probably did not include Cuba or Louisiana where the species seems to be only tenously established.

References:

Whalen, M.D. 1984. Conspectus of species groups in Solanum subgenus Leptostemonum.
Gentes Herbarum 12 (4): 179-282.

Nee, M. 1991. Synopsis of Solanum section Acanthophora: a group of interest for glycoalkaloids.
Pp. 257–266 In: J.G. Hawkes, R.N. Lester, M. Nee, and N. Estrada-R. (eds.). Solanaceae III: Taxonomy, Chemistry, Evolution. Richmond, Surrey, UK: Royal Botanic Gardens, Kew and Linnean Society of London.

Nee, M. 1999. Synopsis of Solanum in the New World.
Pp. 285–333 in M. Nee, D. E. Symon, R. N. Lester & J. P. Jessop (eds.), Solanaceae IV: Advances in Biology and Utilization. Royal Botanic Gardens, Kew.

Levin, R.A., K. Watson & L. Bohs 2005. A four-gene study of evolutionary relationships
in Solanum section Acanthophora.
Amer. J. Bot. 92(4): 603–612.

Bohs, L. 2005. Major clades in Solanum based on ndhF sequences.
Pp. 27-49 in R. C. Keating, V. C. Hollowell, & T. B. Croat (eds.), A festschrift for William G. D’Arcy: the legacy of a taxonomist. Monographs in Systematic Botany from the Missouri Botanical Garden, Vol. 104. Missouri Botanical Garden Press, St. Louis.

Levin, R.A., N.R. Myers, & L. Bohs 2006. Phylogenetic relationships among the "spiny" solanums (Solanum subgenus Leptostemonum).
Amer. J. Bot. 93: 157-169.

Taxonomic name:

Solanum myriacanthum (Solanaceae)

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Solanum myriacanthum

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