n = ploidy missing =12 voucher missing =
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.
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).
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.
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.