Abstract
The Solanum elaeagnifolium clade (Elaeagnifolium clade) contains five species of small, often rhizomatous, shrubs from deserts and dry forests in North and South America. Members of the clade were previously classified in sections Leprophora, Nycterium and Lathyrocarpum, and were not thought to be closely related. The group is sister to the species-rich monophyletic Old World clade of spiny solanums. The species of the group have an amphitropical distribution, with three species in Mexico and the southwestern United States and three species in Argentina. Solanum elaeagnifolium occurs in both North and South America, and is a noxious invasive weed in dry areas worldwide. Members of the group are highly variable morphologically, and this variability has led to much synonymy, particularly in the widespread S. elaeagnifolium. We here review the taxonomic history, morphology, relationships and ecology of these species and provide keys for their identification, descriptions, full synonymy (including designations of lectotypes) and nomenclatural notes. Illustrations, distribution maps and preliminary conservation assessments are provided for all species.
Highlights
Introduction ofS. elaeagnifolium outside of its native range has resulted in its becoming significant weed of cultivation and pasture
None of these are unique to the S. elaeagnifolium group, either in Solanum or in Solanaceae more widely, the dehiscent berries of all these species are only rarely found in Solanum (e.g., S. tununduggae, S. vansittartensis of Australia, see Symon 1981; Knapp 2002a)
Solanum elaeagnifolium is extremely variable in its degree of prickliness; this extreme polymorphism occurs in S. bahamense L. of the Caribbean (Strickland-Constable et al 2000)
Summary
The extremely widespread S. elaeagnifolium was mapped based on GBIF records (http://www.gbif.org/species/2929892; 3,032 georeferenced observations on 6 November 2016) and specimens we have seen. Type specimens with sheet numbers are cited with the herbarium acronym followed by a dash and the sheet number (i.e., MO–1781232); barcodes are written as a continuous string (i.e., G00104280). Following Knapp (2013a) we have used the square bracket convention for publications in which a species is described by one author in a publication edited or compiled by another. These citations are the traditional “in” attributions such as Dunal in DC. S. elaeagnifolium Cav. Solanum ellipticum species group sensu Whalen (1989), S. elaeagnifolium only, excl. Solanum vespertilio group sensu Whalen (1989), S. houstonii only [as S. tridynamum], excl. S. elaeagnifolium, is an invasive weed in dry areas worldwide
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