Although most diverse in the New World tropics, approximately 100 species of Solanum (Solanaceae) are native to continental Africa and Madagascar. The majority of these are ‘spiny solanums’ (subgenus Leptostemonum). We present here the first phylogenetic reconstruction of African and Madagascan species of Solanum subgenus Leptostemonum, with 62 of 76 species native to these areas, plus an additional seven species of largely Asian distribution, using internal transcribed spacer (ITS), waxy and trnT‐F regions. We identify monophyletic groups, many of which correspond to previously recognized units, although the large, traditionally recognized sections of Oliganthes and Melongena are polyphyletic. These groups are distinguished from each other by their breeding systems, with members of Oliganthes being hermaphroditic and Melongena andromonoecious. The phylogenetic relationships suggest multiple changes of breeding system between these two states, and observations of plants across their range indicate that there is considerable lability in this character. The African and Malagasy clades are largely geographically coherent, although there is evolutionary interchange between African vegetation types. All of the Madagascan endemics included in the analysis form a coherent group and probably represent an in situ radiation. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173, 176–193.

Solanum subg. Leptostemonum contains approximately 350-450 species, including the cultivated eggplant, S. melongena. Most species placed in this subgenus form a monophyletic group, the Leptostemonum clade, characterized by the presence of stellate hairs and prickles, leading to the common name of "spiny solanums". Here we present a phylogenetic analysis that circumscribes the major clades within the spiny solanums and examines the relationships among them, with an emphasis on New World species. Of particular interest is the clarification of the clade limits and species composition of groups that have not been well-sampled. We also increase sampling of taxa that have been previously analyzed in molecular studies, namely those in the Torva, Micracantha, and Erythrotrichum clades. These groups have convergent morphological characteristics that have challenged taxonomists, making classification difficult. Results from our study delimit 14 clades within the spiny solanums, including the newly designated Asterophorum, Gardneri, Sisymbriifolium, and Thomasiifolium clades. We also establish the placement of species not previously sampled, especially those endemic to Brazil. These results give an increased understanding of the evolution of the Leptostemonum clade by defining monophyletic groups within it and identify areas of the phylogenetic tree that remain unresolved and require further taxon sampling.

The majority of species in the large genus Solanum (ca. 1500 species) have five-merous, radially symmetrical flowers with equal stamens. However, some Solanum species and groups are characterized by four-merous and/or zygomorphic flowers, unequal stamens and enantiostyly (styles deflected to one side of the flower). Previous workers have used flower and seed coat morphology in these unusual Solanum species as a guide to interpreting their evolutionary relationships. However, the phylogenetic position of the zygomorphic and heterantherous solanums is only beginning to be examined using molecular data and cladistic methodology. DNA sequence data from both the chloroplast and nuclear genomes are used to infer the phylogenetic position of Solanum taxa with variously modified flowers. Zygomorphy and heteranthery have evolved multiple times within Solanum, and most frequently within the spiny solanums (Solanum subg. Leptostemonum). The phylogenies shed light on the disparate morphologies and geographical distributions encountered in the zygomorphic and heterantherous species and pinpoint the likely relatives of these taxa among the actinomorphic Solanum species with equal stamens.

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