Reassessment and typification of Opuntia canterae (Opuntioideae, Cactaceae), an endemic prickly pear cactus of Uruguay

Abstract

Background and aims – Opuntia is the most widespread genus of Cactaceae, naturally occurring throughout arid and semi-arid areas of the Americas. Many of the species have taxonomic problems resulting from incomplete original descriptions, lack of type designations, a paucity of taxonomic revisions and, in general, difficult species delimitation resulting from hybridization, morphological plasticity, and poor specimen preparation. However, efforts are being undertaken to fill the gaps in our distributional, morphological and phylogenetic knowledge of the group. Here, we reassess the name Opuntia canterae, providing an updated description, typification, photographs, distribution map, conservation assessment and additional notes. Material and methods – Extensive fieldwork was conducted, along with comprehensive herbarium and literature review. Morphological characters were assessed based on the commonly used characters used for prickly pears. Species delimitation is proposed based on our morphological studies, taxonomic and literature revision, as well as preliminary phylogenetic studies. The IUCN guidelines were followed to provide a conservation assessment of the species.Key results – Opuntia canterae is reassessed as a distinct species separated from its previous synonym (O. elata) by the elliptic to long-oblanceolate stem segments, acute to conical flower bud apex and long-obconic fruits. An epitype is here designated to further clarify the morphological features of the species, which, heretofore, were only represented by a photo. The species is considered endemic to Uruguay and is provisionally assessed as Endangered (EN) using IUCN criteria, but more fieldwork will be necessary to provide a further precise conservation status.