Solanum robustum
Not known
Southern South America from Brazil to Argentina and Paraguay, in dry to mesic forests and chaco formations, from sea level to 1200 m. Naturalized and possibly invasive in the mountains of Tanzania, often forming large monospecific stands in disturbed habitats such as forest plantations, also sporadically introduced in other subtropical areas (e.g., India)..
Solanum robustum is a member of the Erythrotrichum Clade in subgenus Leptostemonum (the spiny solanums; Stern et al. 2011) and part of a small group within that includes Solanum stagnale and Solanum hexandrum, both Brazilian species.
HDOA (Hawai'i Department of Agriculture). 1992. List of Plant Species Designated as Noxious Weeds for Eradication or Control Purposes (June 18, 1992). Honolulu: Hawai'i Department of Agriculture. Available: http://www.botany.hawaii.edu/cpsu/-strawgua/other/noxious/noxious.html
Stern, S. R., M. de F. Agra, and L. Bohs. 2011. Molecular delimitation of clades within New World species of the ”spiny solanums” (Solanum subgenus Leptostemonum). Taxon 60: 1429-1441.
Wagner, W. L., D. R. Herbst, and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawai'i. 2 vols. Bishop Museum Special Publication 83, University of Hawai'i and Bishop Museum Press, Honolulu, HI.
Local Names. Tanzania: Butwe, mbuntwe (Shambaa language),
Uses. Medicinally used in Tanzania.
[Ecological and morphological discussion based on Africa only - to be completed for American plants]
Solanum robustum is a native of eastern South America and may have been introduced to Africa as an ornamental, as it has been elsewhere (Wagner et al. 1999) for its attractive leaves. It has been classed as a noxious weed in Hawai’i (HDOA 1992), where it was first seen in 1977 (Wagner et al. 1999). The earliest African collection of S. robustum we have seen is from 1909 the Amani area in Tanzania (Braun 2217, EA). Most other collections are from the latter half of the 20th century, perhaps indicating its spread and possible invasive status. This species should be kept under observation for invasiveness, and control contemplated.
The strongly decurrent leaf bases of S. robustum make this species similar to the African Gboma eggplant S. macrocarpon and its wild progenitor S. dasyphyllum. It can be distinguished from those taxa by its softly pubescent leaves, small greenish white stellate flowers and pubescent fruits. Both S. macrocarpon and S. dasyphyllum have larger, rotate flowers and glabrous fruit; S. macrocarpon usually has glabrous or only sparsely pubescent leaves, while S. dasyphyllum is coarsely hairy. Solanum robustum is superficially similar to many other African native species with softly hairy leaves and occasionally somewhat decurrent leaf bases such as S. campylacanthum, S. cerasiferum, S. lichtensteinii, and S. umtuma. The strongly decurrent winged leaf bases, small greenish white stellate corollas and densely pubescent fruits distinguish S. robustum from all these species; the latter have leaves that are not decurrent onto the winged stem, more rotate purple or white flowers, and glabrous fruits.
In describing forms of S. robustum from Paraguay the Swiss botanists Émile Hassler and Robert Chodat cited many syntypes. Chodat’s S. concepcionis var. robustius was based on Balansa 2096, Chodat & Vischer 68, 69, 70 and 71, Rojas 2385 and Hassler 987, 477, 3079 and 7557; this last is the collection selected by Morton (1976) as the lectotype for S. concepcionis. Morton (1976) did not specify or label which of the two sheets of Hassler 7557 at G he designated; here we select the sheet from Hassler’s own herbarium with an annotation in Hassler’s hand as the second stage lectotype for S. concepcionis. Hassler’s own herbarium was donated to G in 1909, but duplicates of his Paraguay collections were widely distributed. We lectotypified these taxa with the G sheets, selecting those syntypes from the original herbaria of the authors where possible and with the most widely distributed duplicates such that none of these taxa is homotypic. Hassler’s S. robustum var. laxepilosum was based on Hassler 2385, 3079 and 11728; as the lectotype we have selected the G duplicate of Hassler 11728 that is the best preserved and bears a field label from Hassler. Solanum robustum forma rupestre was based on Hassler 477 and 987 (overlapping with the specimens used by Chodat in describing var. robustius), Balansa 3127 and Fiebrig 814; we have selected the G duplicate from Hassler’s own herbarium with an annotation in his hand as the lectotype for this name. In describing forma decurrens he cited a single specimen, Fiebrig 5752, in his own herbarium; this is the holotype.