New Solanum species from Tanzanian coastal forests may already be extinct.
The genus Solanum represents a significant gap in our knowledge of the East African flora. The coastal forests of Tanzania are understudied and vulnerable due to habitat loss, and the Ruvu Catchment Forest Reserve in the Morogoro District was not botanically explored prior to the Tanzania Frontier Project in the 1990s. We describe a new Tanzanian endemic species, Solanum ruvu sp. nov., which is known from only one collection. The unusually long inflorescences with a dense covering of long straight prickles on the rachis distinguish S. ruvu from all other African species of spiny Solanum. Its likely affinities lie with another coastal forest species, S. zanzibarense, which exhibits a similar scandent habit, subentire leaves, thin stems, and prickles that are sometimes straight. The Ruvu Forest area is now increasingly populated and planted with rice and sesame. The relict natural vegetation is restricted to small areas of limestone outcrops unsuitable for agriculture and there is no forest canopy to support an understorey species such as S. ruvu. Recent recollection efforts have been unsuccessful and the species is likely to be extinct in the wild.
Keywords: Ruvu, Solanaceae, Solanum subgenus Leptostemonum, coastal forest, Tanzania