African spiny Solanum (subgenus Leptostemonum, Solanaceae): a thorny phylogenetic tangle

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 insitu radiation. (c) 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173, 176-193.