Species identity in the Solanum bahamense species group (Solanaceae, Solanum subgenus Leptostemonum )

The Solanum bahamense L. species group is a small monophyletic group of spiny solanums ( Solanum subg. Leptostemonum ) restricted to the West Indies. The group has been variously recognised as including one to five species, and one of these ( Solanum ensifolium Dunal, as S . drymophilum O.E. Schulz) is listed under the U.S. Endangered Species Act. We here use a combination of morphological characters and plastid sequence data to assess diversity within the group and to explore patterns of differentiation across the archipelago. We recognise three species in the group: S . polyacanthos Lam., endemic to Hispaniola, S . ensifolium Dunal, endemic to Puerto Rico, and S . bahamense L., widespread across the region from the Florida Keys to Grenada, but absent from Hispaniola. Within S . bahamense , three geographically distinct lineages can be distinguished. Maximal genetic diversity in the group occurs in the centre of the archipelago, on Hispaniola and Puerto Rico (including the Virgin Islands). A taxonomic treatment of the three species is provided, with a key, complete typification for all synonyms and exsiccatae (in an Appendix). We recognise the distinctness of S . ensifolium and our data provide support for its inclusion in the Endangered Species Act and its Red List status as critically endangered.