The Morelloid clade, also known as the black nightshades or “Maurella” (Morella), is one of the 10 major clades within the mega-diverse genus Solanum L. The clade is most diverse in the central to southern Andes, but species occur around the tropics and subtropics, some extending well into the temperate zone. Plants of the group vary from herbs to short-lived perennials to perennial shrubs that are distinctly woody at the base, they have small mostly white or purplish white flowers and small juicy berries. Due to the complex morphological variation and weedy nature of these plants, coupled with the large number of published synonyms (especially for European taxa), our understanding of species limits and diversity in the Morelloid clade has lagged behind that of other clades in Solanum. Here we provide the last in a three-part series of monographic treatments of the morelloid solanums (see PhytoKeys Vols. 106, 125), treating the 62 species occurring in South America. This region is by far the most diverse in the clade, both in terms of species number and morphological diversity. We provide complete synonymy, nomenclatural details, including lecto- and neotypifications where needed, common names and uses, morphological descriptions, illustrations to aid identification both in herbaria and in the field, and distribution maps for all native, non-cultivated species. We include a key to all species, a synoptic character list for the species treated here and links to synoptic online keys for all species of the Morelloid clade. Preliminary conservation assessments following IUCN guidelines are also provided for all native species.
