A revision of the Old World Black Nightshades (Morelloid clade of Solanum L., Solanaceae)

Abstract

The Morelloid clade, also known as the black nightshades or “Maurella” (Morella), is one of the 10 major clades within Solanum L. The pantropical clade consists of 75 currently recognised non-spiny herbaceous and suffrutescent species with simple or branched hairs with or without glandular tips, with a centre of distribution in the tropical Andes. A secondary centre of diversity is found in Africa, where a set of mainly polyploid taxa occur. A yet smaller set of species is found in Australasia and Europe, including Solanum nigrum L., the type of the genus Solanum. Due to the large number of published synonyms, combined with complex morphological variation, our understanding of species limits and diversity in the Morelloid clade has remained poor despite detailed morphological studies carried out in conjunction with breeding experiments. Here we provide the first taxonomic overview since the 19th century of the entire group in the Old World, including Africa, Asia, Australia, Europe and islands of the Pacific. Complete synonymy, morphological descriptions, distribution maps and common names and uses are provided for all 19 species occurring outside the Americas (i.e. Africa, Asia, Australia, Europe and islands of the Pacific). We treat 12 species native to the Old World, as well as 7 taxa that are putatively introduced and/or invasive in the region. The current knowledge of the origin of the polyploid species is summarised. A key to all of the species occurring in the Old World is provided, together with line drawings and colour figures to aid identification both in herbaria and in the field. Preliminary conservation assessments are provided for all species.

A new black nightshade (Morelloid clade, Solanum, Solanaceae) from the caatinga biome of north-eastern Brazil with a key to Brazilian morelloids

“…Specimens of this species may be found identified as S.americanum in other herbaria, but in our extensive work on the morelloid solanums in European, American and Latin American herbaria (see Särkinen et al 2018), we have failed to find collections other than those cited here. Specimens (1,241 in total) included in the Suppl.…”

“…material 1 are those morelloids occurring in Brazil for which we have examined material from 68 herbaria worldwide; many of these are not yet georeferenced but will be as we complete the monographic treatment of this group for South America (e.g. see Särkinen et al 2018). The specimen data are included here to assist herbarium curators with species identification.…”

“…S.nigrum L., S.retroflexum Dunal, S.villosum Mill.) are polymorphic for presence or absence of glandular trichomes and their occurrence does not correlate with relationships based on phenetic studies with molecular markers (Manoko 2007; see Särkinen et al 2018 for a discussion). In the Americas, however, glandular pubescence is correlated with other characters such as anther length and stone cell presence or absence, suggesting it can be of taxonomic significance.…”

“…The clade includes five major groups traditionally recognised at the sectional level (sections Solanum , Campanulisolanum Bitter, Parasolanum A.Child pro parte, Chamasarachidium Bitter and Episarcophyllum Bitter), which are in the process of re-circumscription based on molecular results (Särkinen et al 2015c). The black nightshade group (sectionSolanum sensu D’Arcy 1972; see Särkinen et al 2018) is the largest of these with ca. 52 species and ca.…”

“…These stone cells are derived from accretions of sclerenchyma in the mesocarp (Bitter 1911, 1914; Danert 1969). Although some studies have been undertaken to clarify the taxonomy of the Old World and North American species of the Morelloid group (Edmonds 1977, 1978; Schilling 1981; Särkinen et al 2018), a monographic study is needed to aid species identification and to clarify synonymy, especially in Andean South America where most of the species diversity is found (Edmonds 1972; Barboza et al 2013) and where the Morelloid clade is amongst the most diverse groups of Solanum . The weedy nature of many of the common species of the group means that distinct taxa are often identified as common species and collections are often not made because botanists consider these plants uninteresting weeds (see Särkinen et al 2013a for a typical case).…”