| The monophyly and phylogenetic relationships of the Solanum dunalianum group have been the subject of controversy. The S. dunalianum group was investigated using fifty-eight morphological characters and DNA sequence data: molecular markers ITS, trnT-trnF, and waxy. The individual datasets, combined molecular dataset, and total evidence dataset were analyzed under the parsimony criterion. In all analyses, the S. dunalianum group was resolved as not monophyletic, necessitating taxonomic realignment. In the total evidence strict consensus, all species of the Solanum dunalianum group, except S. tetrandrum, fell into either of two clades, compatible with the previously proposed Solanum sections Dunaliana and Irenosolanum. Solanum tetrandrum was resolved with S. melongena indicating an affinity with species from tropical Asia. Solanum section Dunaliana was sister to New Guinean species of the S. ferocissimum group. Solanum section Irenosolanum was sister to a clade of Australian and New Guinean species of various groups. No unique synapomorphies support either section, but morphological trends exist. Taxonomic treatments for each section are presented. Both include a key to species, distribution maps, and images of type specimens. Solanum section Dunaliana, centered on New Guinea, is restricted to a morphologically coherent clade of six species including S. labyrinthinum named herein. It is characterized by a large shrub or small tree habit, sparse, broad-based prickles, entire leaves with the blade unarmed, many-flowered inflorescence with all flowers fertile, corollas with poorly developed interpetalar tissue, and juicy, red fruit. A neotype is designated for S. peekelii; lectotypes are designated for S. dunalianum var. inerme and S. torricellense. Solanum section Irenosolanum is comprised of twenty-nine species, the following seven of which are named as new herein: Solanum albertii, S. memaoyanum, S. nudatum, S. pseudopedunculatum, S. ratale, S. semisucculentum, and S. vanuatuense. Solanum section Irenosolanum is morphologically diverse; tendencies include: paucity or absence of prickles, spreading (non-connivent) anthers, white corollas, and horizontal presentation of flowers. The section is restricted to the islands of the Pacific; all native species of Solanum subgenus Leptostemonum from the Pacific belong to section Irenosolanum except S. lasiocarpum and S. repandum of section Lasiocarpa. Thirty taxa including Solanum section Irenosolanum are typified. |
