Solanum roseum
Cloud forest, 1500-2500 m elevation, western Bolivia in Department of La Paz and perhaps also southern Peru.
Solanum roseum belongs to the Cyphomandra clade of Solanum along with other species traditionally recognized in sections Pachyphylla and Cyphomandropsis (Bohs, in press a). Within the Cyphomandra clade, S. roseum belongs to a well-supported clade that also includes S. maternum, S. betaceum, and S. unilobum (Bohs, in press b).
Bohs, L. 1991. Crossing studies in Cyphomandra (Solanaceae) and their systematic and evolutionary significance.
Amer. J. Bot. 78: 1683-1693.
Bohs, L. 1994. Cyphomandra (Solanaceae).
Flora Neotropica Monograph 63: 1-175. New York Botanical Garden, Bronx, NY.
Bohs, L. 1995. Transfer of Cyphomandra (Solanaceae) and its species to Solanum.
Taxon 44: 583-587.
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.
Bohs, L. 2007. Phylogeny of the Cyphomandra clade of the genus Solanum (Solanaceae) based on ITS sequence data.
Taxon 56: 1012-1026.
nuclear ITS sequence: GenBank AY523915 (voucher: Bohs 2338, GH). nuclear ITS sequence: GenBank AY523916 (voucher: Nee et al. 51776, NY).
Solanum roseum is most closely related to S. betaceum, S. maternum, and S. unilobum. Solanum roseum, S. maternum, and S. unilobum are endemic to Bolivia, whereas the native range of S. betaceum extends from southern Bolivia into northwestern Argentina. The pinkish, stellate corollas of S. roseum are similar to those of S. betaceum and S. maternum, but S. roseum differs in its nearly glabrous leaves and stems, narrow leaf blades, and very large seeds. Hybrids have been produced in the greenhouse between S. betaceum and S. roseum (Bohs, 1991) and molecular data confirm that all four species are closely related (Bohs, in press b).
Solanum roseum is often nearly indistinguishable from S. unilobum on herbarium sheets. Both species are found in the Bolivian Yungas, but the range of S. unilobum also extends to forests of central Bolivia. Solanum roseum occurs above 1500 m in elevation, whereas S. unilobum is found more often at lower elevations. Both species have ovate, cordate leaf blades and sparse, inconspicuous pubescence, but S. unilobum has broader leaves with deeper basal lobes and is generally more pubescent than S. roseum. Solanum roseum has purplish or reddish corollas with dark reddish connectives, in contrast with the green, yellow green, or whitish corollas and bright yellow anther connectives of S. unilobum. The stigma of S. roseum, although slightly dilated at the apex of the style, is not as broad as that of S. unilobum and lacks the two conspicuous apical glands present in the latter species.
Solanum roseum can be distinguished from all other species in Solanum section Pachyphylla by its unusually large and conspicuously brown-pubescent seeds. Other species of the section with large seeds, such as S. circinatum, S. endopogon, and S. sibundoyense, have whitish seed hairs generally less than 1 mm long.
The collection of Plowman and Davis 4929 (F, GH) from Prov. Paucartambo, Dept. Cuzco, Peru may belong to S. roseum. The fruits and seeds agree with those of S. roseum, but the leaves have truncate or cuneate rather than cordate bases. The specimens bear only fruits, so a decision to include them in S. roseum or describe them as a new species must await further collections in Peru.