Taxonomy of the Australian Nicotiana benthamiana complex (Nicotiana section Suaveolentes; Solanaceae): five species, four newly described, with distinct ranges and morphologies

Although some authors previously questioned the circumscription of Nicotiana benthamiana, it has never been treated taxonomically as more than a single widespread, variable species. A recent study employing phylogenetic and population genetic analyses has demonstrated that N. benthamiana comprises five species that are geographically and morphologically distinct. Here, we describe four new species in the N. benthamiana complex, namely, N. bilybara M.W.Chase & Christenh., N. candelabra M.W.Chase & Christenh., N. rupestris M.W.Chase & Christenh. and N. scopulorum M.W.Chase & Christenh., and illustrate all five. We provide descriptions, a diagnostic key and a table of morphological characters distinguishing these closely related species. The major morphological feature that distinguishes N. benthamiana from the other four species is its petiolate leaves that become sessile only near the apex of the inflorescence; N. candelabra is distinct in its bifacial branching, N. bilybara in its commonly winged petiole with an auriculate base, N. rupestris in the leafy apices of its calyx lobes, and N. scopulorum is the least morphologically divergent species, conforming most closely to the general description of the N. benthamiana species complex.