Weedy shrub of forest clearings, thickets, pastures, roadsides, coffee plantations, ravines, streamsides and perhaps within the forest itself. At moderate altitudes, ranging from 800 to 2400 m, but most collections from between 1200 and 2000 m, in rainforest, cloud forest or oak-pine (only in northern Central America) zones. In the Cordillera from southern Mexico to Peru and easterwards through Venezuela to Trinidad, also in eastern Brazil and eastern Paraguay. Probably more tolerant of shade than its near relative S. atropurpureum.
Solanum acerifolium belongs to group of species with conspicuous wings surrounding the periphery of the seeds in sect. Acanthophora in subgen. Leptostemonum (Nee, 1979, 1991, 1999). Within this unnamed subsection (Nee, 1999) it is strongly supported as sister to S. atropurpureum + S. tenuispinum (Levin et al., 2005). Solanum acerifolium belongs to the Leptostemonum clade of Solanum (Bohs, 2005). The Acanthophora clade is 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).
This species can be confused with S. atropurpureum but the leaves are much less deeply lobed. The similar S. tenuispinum of Argentina, Bolivia and Peru is scarcely sympatric and has longer pedunculate inflorescences with more flowers, although in other respects they are sometimes difficult to separate.
The status of this species in Brazil is problematical; all but four of the collections date from before 1900 and the latest collection is from 1922, despite its wide distribution there. Variation is present on some Brazilian specimens that is rare or absent elsewhere, e.g. leaf lobing or the glossy look of the glabrous upper leaf surface (Riedel 1075; Löfgren 781, 1385; Peckolt 35). The scattered Brazilian collections were previously excluded from S. acerifolium in a discussion of its geography (Nee, 1979), but I am now including them. Most agree perfectly with material from the main range, while none cited here differs in any fundamental characters. The leaf shape of S. acerifolium is so variable that additional shapes are not too surprising. The few atypical collections cannot be equated with any other Brazilian species and in any case would be most closely related to S. acerifolium even if a few of the collections eventually prove to belong to a different species.
Very little habitat data can be gleaned from the pre-1900 Brazilian collections, but it presumably has a similar ecology to that elsewhere. The collections from Pernambuco (Swainson s.n.) attributing it to "catinga woods" surely does not mean that it inhabits the thorn scrubland with many Cactaceae and terrestrial bromeliads which is the modern concept of "caatinga" vegetation of the semiarid interior of the Brazilian Nordeste.
A possibility is that the distribution of S. acerifolium is somehow related to coffee production. It is commonly found in and around coffee plantations, both producing and abandoned. It is possible that the Brazilian collections represent sporadic introductions from coffee producing areas of the Andes or Central America. Alternatively, it could be native to Brazil and has become introduced into the rest of its range inadvertently with commerce.
In 21 of 93 (22%) labels on which flower color is noted, the flower is said to be white. I suspect this represents laxness on the part of collectors and that the corolla is a rather uniform light yellowish green, perhaps fading to a lighter color as the corolla ages.
Nee, M. 1979. Patterns in biogeography in Solanum, section Acanthophora.
Pp. 569–580 in J. G. Hawkes, R. N. Lester & A. D. Skelding (eds.), The Biology and Taxonomy of the Solanaceae. Academic Press, London.
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.
chloroplast trnS-G sequence: Genbank AY555454 (voucher Bohs 2714, UT). http://www.ncbi.nlm.nih.gov/entrez/viewer.fcgi?db=nucleotide&val=49065894 nuclear waxy (GBSSI) sequence: GenBank AY562949 (voucher: Bohs 2714, UT). http://www.ncbi.nlm.nih.gov/entrez/viewer.fcgi?db=nucleotide&val=45826380 chloroplast trnT-F sequence: GenBank AY266249 (voucher: Bohs 2714, UT). http://www.ncbi.nlm.nih.gov/entrez/viewer.fcgi?db=nucleotide&val=33355750 nuclear ITS sequence: GenBank AY561261 (voucher: Bohs 2714, UT). http://www.ncbi.nlm.nih.gov/entrez/viewer.fcgi?db=nucleotide&val=49458079