Abstract
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 species rich 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 are herbaceous or short-lived perennials, with small 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 major groups in Solanum. Here we provide the second in a three-part series of revisions of the morelloid solanums treating the species occurring in North and Central America and the Caribbean (for the Old World see “PhytoKeys 106”, the third part will treat species of South America). Synonymy, morphological descriptions, distribution maps, and common names and uses are provided for all 18 species occurring in this region. We treat 10 of these species as native, and eight as putatively naturalised, introduced and/or invasive in the region. We provide complete descriptions with nomenclatural details, including lecto- and neotypifications, for all species. Keys to all species occurring in the whole region and for each area within it (i.e., North America, Central America and Mexico, and the islands of the Caribbean), illustrations to aid identification both in herbaria and in the field, and distribution maps are provided. Preliminary conservation assessments are provided for all species. Details of all specimens examined are provided in three Supplementary materials sections.
Highlights
Solanum L., with approximately 1,400 species, is one of the largest genera of flowering plants (Frodin 2004)
The name S. americanum has been in common use in North America (e.g., Stebbins and Paddock 1949) for what is known as S. emulans, but more recently (Schilling 1981) the two taxa have been distinguished and the name S. ptychanthum has been used for the taxon for which the oldest name is S. emulans
Solanum chenopodioides can be distinguished from S. pseudogracile only with difficulty, but the short-triangular calyx lobes with acute apices that remain appressed to the berry at fruit maturity, as opposed to the longer, rectangular calyx lobes with rounded to acute apices that are reflexed in fruit of S. pseudogracile, are characters that distinguish the taxa
Summary
Solanum L., with approximately 1,400 species, is one of the largest genera of flowering plants (Frodin 2004). Like some other groups of non-spiny solanums such as the Pachystemonum (Cyphomandra) Clade (Bohs 1998) and the Archaesolanum Clade (Symon 1994) berries of members of the Morelloid Clade contain small, hard inclusions commonly referred to as sclerotic granules, stone cells or brachysclereids (Bitter 1911, 1914; in species descriptions here referred to as stone cells) These concretions are composed of modified sclerenchyma cells with massively enlarged cell walls (Fig. 2G, H); the stone cells of pears and quinces (Rosaceae) are classic examples of this cell type. Sometimes stone cells of different sizes are found in the same berry, but this character is not consistent within species The number of these is usually relatively consistent within a species, and varies from absent (e.g., S. chenopodioides, S. retroflexum, S. scabrum, S. villosum) to (1)2–4(–6) (e.g., S. interius, S. macrotonum, S. nigrescens) to more than 10 (e.g., S. furcatum, S. triflorum). Infraspecific taxa have been recognised by others within the group, we do not recognise any here due to the complex morphological variation observed within each species, where the inspection of large number of specimens quickly reveals no apparent natural breaks in variation but rather a mixing between highly morphologically variable populations of widespread species
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