A new dioecious bush tomato, Solanum nectarifolium (Solanaceae), from the northern Tanami Desert, Northern Territory, Australia, with reassessment of S. ossicruentum and a change in the circumscription of S. dioicum

A new species of functionally dioecious bush tomato from the “ Solanum dioicum + S. echinatum group ” of Solanum subgenus Leptostemonum is described. Solanum nectarifolium Martine & Brennan, sp. nov., is a member of the taxonomically challenging Solanum dioicum W. Fitzg. species complex in Australia and differs from other species in the group by the presence of prominent and conspicuous extrafloral nectaries on the abaxial leaf surfaces, a tinge of purple on the new growth and young fruiting calyces, and curved prickles on young stems.

Although fairly well represented in herbarium collections, this new taxon has historically been treated as a part of S. dioicum and more recently as a part of S. ossicruentum Martine & J. Cantley due to shared vegetative characters, particularly a silvery-blue aspect. Symon’s “ Group three ” or “ Tanami form ” of S. dioicum is thus now treated as two species: S. nectarifolium (with prominent nectaries, a deeply bifid stigma, and an exposed berry at maturity) and S. ossicruentum (lacking visible nectaries and possessing a slightly lobed and nearly linear stigma, plus a berry fully enclosed in the calyx at maturity).

While extrafloral nectar production has been documented in Solanum, S. nectarifolium is the first known example in the genus with nectaries that are consistently visible to the naked eye. This new species brings the number of functionally dioecious (and morphologically androdioecious) Solanum species in Australia to 15. We also provide an updated distribution for S. ossicruentum and, in light of our findings, reassess the identity of specimens associated with the type series for S. dioicum.