Solanum stagnale
2n = ploidy missing =24 voucher missing =
Distribution: Known only from coastal Brazil in the state of Bahia, apparently growing very near the seashore.
Solanum stagnale belongs to the Leptostemonum clade of Solanum (Bohs, 2005). Although Whalen et al. (1981) considered S. stagnale to belong to Solanum section Lasiocarpa, they noted that it was anomalous and “phylogenetically isolated” within the section. In Whalen (1984), S. stagnale is removed from section Lasiocarpa and placed in the S. polytrichum group, comprising about eight species centered in southeastern Brazil, Paraguay, northern Argentina, and southeastern Bolivia. However, he notes that S. stagnale lacks the prickly pedicels and calyces of the other members of the S. polytrichum group. In addition, the fruits of S. stagnale are pubescent, in contrast to the usually glabrous berries of the other members of the S. polytrichum group. Molecular phylogenetic studies of Bohs (2004) and Levin et al. (2005, 2006) based on chloroplast and nuclear sequence data confirm that S. stagnale is not related to members of Solanum section Lasiocarpa (the Lasiocarpa clade of Levin et al., 2006). Instead, S. stagnale emerges as sister to S. robustum and belongs to a clade termed the Robustum clade of Levin et al. (2006) including S. accrescens, S. robustum, S. stagnale, S. agrarium, S. stenandrum, and S. microphyllum. Solanum stagnale and S. robustum share decurrent leaf bases, felty whitish or reddish pubescence, and abundantly pubescent fruits. Solanum accrescens, a representative of the S. erythrotrichum group, also has pubescent fruits.
Whalen, M.D., D.E. Costich & C.B. Heiser, Jr. 1981. Taxonomy of Solanum section Lasiocarpa.
Gentes Herb. 12: 41-129.
Whalen, M.D. 1984. Conspectus of species groups in Solanum subgenus Leptostemonum.
Gentes Herbarum 12 (4): 179-282.
Bohs, L. 2004. A chloroplast DNA phylogeny of Solanum section Lasiocarpa (Solanaceae).
Syst. Bot. 29: 177-187.
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.
nuclear ITS sequence: GenBank AY561272 (voucher: Carvalho 3213, IND) nuclear waxy (GBSSI) sequence: GenBank AY562968 (voucher: Carvalho 3213, IND) chloroplast trnS-G sequence: GenBank AY555474 (voucher: Carvalho 3213, IND) chloroplast trnT-F sequence: GenBank AY266262 (voucher: Bohs 3094, UT)
Commentary of Whalen et al. (1981):
We were able to locate only one collection of S. stagnale in major American herbaria, so the species is not well known to us. We hope that a search for it in the wild in Bahia and in Brazilian herbaria will eventually turn up more material. Living collections are especially needed. Essentially nothing is known of the properties of the fruit or of other characteristics that may be of value in breeding programs. We are not aware of any collections made more recently than the middle nineteenth century, and the region from which these came is now densely populated. It is important that the current status of S. stagnale in the wild be investigated and that living material be brought into cultivation.
Solanum stagnale is phylogenetically isolated in section Lasiocarpa. Some anomalous characters of the species are the reddish pubescence, decurrent leaf blades with stipitate stellae on adaxial surfaces, and the well-developed lateral rays of pericarp stellae. Although S. stagnale is distant from the other species, there is little justification for its exclusion from section Lasiocarpa. It shares all the synapomorphic characters that define the section, except reduced lateral rays on fruit trichomes.
Commentary of Bohs (2005):
Molecular data clearly place S. stagnale outside of sect. Lasiocarpa. Furthermore, they ally it with S. accrescens, a member of S. sect. Erythrotrichum. Solanum sect. Erythrotrichum is notable for its ferruginous pubescence and, often, decurrent leaf bases. Based on molecular and, in hindsight, morphological data, it is almost certain that S. stagnale should be considered a member of S. sect. Erythrotrichum.