We are the Crystal Gems: taxonomic revision of the gem-fruited species of Commelina L. (Commelinaceae, Commelinales) and their allies

We present a taxonomic revision of the gem-fruited species of Commelina and their allies. We address misapplied names, taxonomic confusion, and undescribed taxa based on a combination of macro- and micromorphological characters, ecological and reproductive data, and preliminary molecular data for Commelina. We recognise a total of 14 species, including two new species, Commelina almandina M.Pell. & Cornejo sp. nov. and C. sugariae M.Pell. sp. nov., and five reestablished ones previously treated as synonyms. We provide an identification key to the gem-fruited species of Commelina and their closest allies, as well as complete morphological descriptions, images, comments, and distribution maps for all recognised species. Species are recognised based on a unique combination of discrete vegetative (i.e., root and rhizome morphology, stem posture and growth pattern, leaf-sheath morphology, phyllotaxy, and leaf-blade morphology) and reproductive (i.e., synflorescence architecture, inflorescence position, spathe morphology, upper cincinnus development and flower production, pedicel pubescence, sepal morphology, petal morphology, filaments’ posture at anthesis, anthers and antherodes morphology, gynoecium and fruit morphology, fruit dehiscence, and seed morphology) morphological characters. We also provide comments and corrections on the taxonomy, application, and nomenclature of names historically associated with or confused with species of gem-fruited Commelina. Finally, we provide a general overview of poorly explored characters and issues plaguing the taxonomy of Commelina.