DOI: 10.15468/y5uryg
title: Taxonomic revision of Saxicolella (Podostemaceae), African waterfall plants highly threatened by Hydro-Electric projects

description: This dataset contains the digitized treatments in Plazi based on the original journal article Cheek, Martin, Molmou, Denise, Magassouba, Sekou, Ghogue, Jean-Paul (2022): Taxonomic revision of Saxicolella (Podostemaceae), African waterfall plants highly threatened by Hydro-Electric projects. Kew Bulletin 77 (2): 403-433, DOI: 10.1007/s12225-022-10019-2, URL: http://dx.doi.org/10.1007/s12225-022-10019-2Summary. Species of the genus Sapicolella Engl. (Podostemaceae) are African rheophytes, restricted to rapids and waterfalls as are all members of the family. Previously, Sapicolella sensu lato was shown to be polyphyletic with two separate clades. The name Pohliella Engl. was recently resurrected for one clade that is sister to the American genera Ceratolacis (Tul.) Wedd., Podostemum Michx. and all Old World Podostemoideae. Pohliella has distichous phyllotaxy, bilocular ovaries, filiform roots with paired holdfasts, and rootcaps. The second clade, Sapicolella sensu stricto, including the type of the generic name, has spiral phyllotaxy, unilocular ovaries, ribbon-like or crustose roots that lack both holdfasts and rootcaps. Sapicolella sensu stricto, sampled from the type species, S. nana Engl. of Cameroon, is embedded within and near the base of the major clade of African podostemoids and is sister to all other African genera apart from Inversodicraea R.E.Fr. and Monandriella Engl. Recently reduced to three species in Cameroon and SE Nigeria by the resurrection of Pohliella, Sapicolella sensu stricto is expanded to eight species in this monograph by description of five new taxa. Sapicolella futa Cheek and S. deniseae Cheek are newly described from Guinea, S. ijim Cheek from Cameroon, the informally named S. sp. Afrom Gabon, and S. angola Cheek from Angola. The known geographic range of the genus is thus expanded c. 2,500 km westwards to Guinea from eastern Nigeria and c.1,500 km southeastwards from near Yaoundé to Cuanza do Sul, Angola. The greatest concentration of species occurs in the Cross-Sanaga interval of western Cameroon and eastern Nigeria, with three species. Cameroon (2 species) followed by Nigeria and Guinea (2 species each) are the countries with highest species diversity. A classification is proposed grouping the species into three subgenera (Sapicolella, Butumia (G.Taylor) Cheek comb. et stat. nov. and Kinkonia Cheek subgen. nov.) based on root morphology and shoot position and morphology. The discovery, morphology, circumscription, distribution and ecology of Sapicolella is reviewed, an identification key to the species is presented, together with descriptions, synonymy and links to illustrations. All of the species are provisionally assessed as either Endangered or Critically Endangered using the IUCN 2012 Red List Criteria. The major threats, above all, are hydro-electric projects. Sapicolella deniseae may already be globally extinct, and two of the four known locations of S. angola appear lost, S. sp. Aof Gabon is threatened at at least one of its three locations, while S. futa is threatened at all three locations. Contamination of watercourses by increased turbidity from silt-load due to anthropic changes and by eutrophication from pollution are also threats for the majority of the species.