Solanum argentinum
n = ploidy missing =12 voucher missing = (Moscone 1992)
Bolivia, Argentina and Paraguay, primarily a species of Chaco habitats, but in many secondary habitats in a wide range of elevations from 100-3000 m.
Solanum argentinum is a member of the Geminata clade (sensu Bohs, 2005). It appears to be related to the members of the Solanum pseudocapsicum species group of Knapp (2002).
Knapp, S. 1989. A revision of the Solanum nitidum species group (section Holophylla pro parte: Solanaceae).
Bull. Br. Mus. Nat. Hist. (Bot.) 19: 63-112.
Knapp, S. 2002. Solanum section Geminata (G. Don) Walpers (Solanaceae).
Flora Neotropica 84: 1-405.
Rigonatto, O., N. Dottori & M.T. Cosa 2005. Anatomía de órganos vegetativos en Solanum argentinum (Solanaceae).
Kurtziana 31: 21-28.
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.
Knapp, S. 2008. A revision of the Solanum havanense species group (section Geminata (G. Don) Walp. pro parte) and new taxonomic additions to the Geminata clade (Solanum: Solanaceae).
Ann. Missouri Bot. Gard.
I excluded Solanum argentinum from section Geminata based on its complex, branched inflorescence, and thought it possibly was more closely related to members of section Holophylla s.s. such as S. aligerum Schltdl. (Knapp, 2002). Analyses of chloroplast DNA sequences (Bohs, 2005) show that S. argentinum is firmly imbedded in the Geminata clade, and that it is apparently close to S. pseudocapsicum L. and its relatives. Closer analysis of inflorescence morphology revealed that S. argentinum lacks the distinctive platform pedicel base morphology of S. aligerum and relatives (see Knapp, 1989), and that the inflorescence, despite its highly branched character, is similar to those elsewhere in the Geminata clade. Solanum argentinum shares with other members of the S. pseudocapsicum species group (sensu Knapp, 2002) brightly colored fruit with red or orange pericarp, yellow, flattened seeds, and pedicels that are nodding in flower and erect in fruit.
Individual plants of S. argentinum vary enormously in pubescence density, from nearly glabrous to densely pubescent over the entire abaxial leaf surface. This variability in pubescence density led to the description of the two taxa now synonymized under S. argentinum, and is not different in anything other than degree (Rigonatto et al., 2005). Rigonatto et al. (2005) examined trichome and leaf surface morphology along the range of pubescence densities and found no differences that would lead them to regard them as different taxa, even at the subspecific level. Puebescence density may also vary in response to environmental variables such as aridity or elevation. To test this possibility I scored mature leaves (four leaves below the growing tip of a shoot) into three classes of pubescence density on 160 geo-referenced specimens with elevation recorded (see Knapp, 2007) from throughout the species range. Each duplicate of a given collection was scored separately, as some collections were obviously not from the same plant (i.e. they were very different in pubescence density). The scoring was a simple three point scale: 1 = glabrous, 2 = tufts of trichomes in the vein axils, 3 = pubescence on the entire lamina. No effect of latitude, longitude or altitude was apparent and the confidence limits of each pubescence class overlapped for each environmental variable (see Knapp, 2007). Local populations of S. argentinum are often composed of large continuous patches of plants of identical pubescence density. My observations of populations in eastern Bolivia (e.g. Nee et al. 51722, 51723) suggest to me that the species may be clonal, or spreading through underground connections. This, however, has not yet been investigated.
Solanum argentinum is a widespread and weedy species. It can be assigned a preliminary conservation status of Least Concern (LC).