| The heart of systematics lies in understanding the diversity of organisms, including the discovery, description, classification, and the relationships between them. Here, I examine the systematics of the plant genus Solanum (Solanaceae), specifically, species within the large Leptostemonum clade. The Leptostemonum clade contains ca. 350--450 species and is characterized by the presence of stellate hairs and epidermal prickles, leading to the common name of the "spiny solanums." Here, I present three studies within the spiny solanums. First, I present a molecular phylogenetic analysis of a group of ca. 12 species known as Solanum section Androceras . Many unusual morphological features, including zygomorphic flowers, dry fruits enveloped by a tightly accrescent calyx, and unique chemical compounds, characterize this group. I use molecular phylogenetic techniques to examine the monophyly of this group, clarify the relationship between section Androceras and closely related members of the spiny solanums, and resolve the relationships between species within the section. Second, I present a molecular phylogenetic analysis of the new world members of the Leptostemonum clade to circumscribe the major clades and examine the relationships between them. Specifically, I increase taxon sampling of many of the large groups underrepresented in previous studies, including sections and species that have not previously been sampled, to delimit 14 clades within the spiny solanums. Finally, I present a taxonomic revision of Solanum section Eriophyllum, a group of 12 viny species native to the Neotropics. In this revision, I review the morphology, taxonomic history, nomenclature, ecology, distribution, reproductive biology, and phylogeny of the section. The results of these studies will help to increase our understanding of a large, economically important group of plants. |
