A synoptic revision of Inversodicraea (Podostemaceae)

Six new species of Inversodicraea (I. feika from Sierra Leone, I. liberia from Liberia, and I. ebo, I. eladii, I. tchoutoi, and I. xanderi from Cameroon) are described as new to science in the context of a synoptic revision of this African genus, now comprising 30 species, including I. cussetiana comb. nov., newly transferred from Macropodiella. Inversodicraea is now equal in number of species to Ledermanniella (as redefined), as the largest genus of the family in Africa. Terete or slightly dorsiventrally flattened leaf petioles (not sheathing and/or stipulate) are newly discovered to distinguish the genus from Ledermanniella, in addition to the presence of scale-leaves. Inversodicraea boumiensis, I. annithomae, and I. bosii are redelimited in this paper. Examples of species hybrids are discussed. Eighteen species are point endemics. A key and IUCN 2012 standard conservation assessments for all species are included. 28 of the 30 species have been assessed as Threatened or Near Threatened. Hydroelectric projects are the biggest source of extinction risk to species of the genus, threatening 19 of the 30 species.