Four New Pauridiantha Species (Rubiaceae) Reflect the Richness of Gabon's Rainforests

Four new Pauridiantha species are described and illustrated. Pauridiantha longistipula Ntore & Dessein is found in the northern part of the Crystal Mountains of Gabon and the neighboring region of Equatorial Guinea, and is easily characterized by its very long stipules. Pauridantha barbata Ntore & Dessein, collected from the southern sector of the Moukalaba-Doudou National Park in Gabon and the Kouilou department in the Republic of the Congo, resembles P. mayumbensis, but differs inter alia in the absence of leaf domatia and barbate corolla buds. The two other new species are endemic to Gabon. Pauridiantha triflora Ntore & Dessein, from the Doudou Mountains and the Chaillu Massif, is somewhat similar to P. smetsiana, but differs in the hairy stems, leaves and inflorescences, the smaller green-drying leaves and the narrowly triangular stipules. Pauridiantha uniflora Ntore & Dessein, only known from the Crystal Mountains area, is easily confused with P. talbotii, but differs in the smaller, ovate leaves with short acumen, the less ascending secondary veins, and the mid-vein hairy above. Apart from the descriptions, a key to all Pauridiantha species from Gabon is provided and a conservation status of the new species following the IUCN criteria is given.