A microendemic and enigmatic new cactus species from the campo rupestre of Minas Gerais, Brazil: Uebelmannia nuda (Cactaceae, Cactoideae)

A phylogenetic study of Uebelmannia investigates the relationships of a newly discovered taxon in this enigmatic, early‐diverging genus that is sister to all the other c. 460 species of tribe Cereeae. Here we present a coalescent‐based phylogenetic tree inferred with nuclear genes captured by the Cactaceae591 probe set encompassing all Uebelmannia species. The new taxon U. nuda is sister to U. pectinifera, while U. gummifera and U. buiningii form another pair of closely related species. The unusual characteristics of the new cactus (semi‐subterranean/geophytic habit, turbinate stem, naked areoles) distinguish it from all other Uebelmannia species. The definition of the relationships within this early‐derived genus endemic to the campo rupestre of Minas Gerais State became more evident, and this new find adds to the importance of this biogeographic province for the evolution of tribe Cereeae. The new species is described, and a preliminary conservation assessment is presented. Additionally, a key for all taxa of the genus is provided.