A A new species of Graffenrieda (Melastomataceae) from the northern Andes, Caquetá, Colombia, and a key for the Graffenrieda group with calyptrate flowers

Background and Aims: Graffenrieda is a Neotropical genus with more than 70 species, mainly distributed in the Guiana Shield and the Andes. This work describes a new species of Graffenrieda and provides a key to identify all species with calyptrate flowers in the genus.Methods: The description of this new species was made from collections deposited in the Colombian herbaria JBB and COAH. Measurements of vegetative parts and inflorescence were made from dried material, while floral structures and fruits were measured from fresh material preserved in alcohol. Their conservation status was assessed according to IUCN guidelines. A key for the recognition of all species of the genus with calyptrate flowers, including the new species and Centronia species to be transferred to Graffenrieda is also provided here, for which lists of species in Neotropical countries, collection databases, and literature on both genera were consulted.Key results: Graffenrieda cardenasii sp. nov. is endemic to the southern Cordillera Oriental of Colombia and is characterized by its indumentum of irregular lepidote trichomes on the vegetative parts, leaves with incomplete lateral anisophylly, leafy bracteoles as large as the flower buds, 5-merous flowers, calyptrate calyx and 2-locular ovary. It is categorized as Endangered in view of its endemicity and habitat specificity. A key is provided for 30 species of the genus Graffenrieda that share the character of calyptrate flowers.Conclusions: This species is named in honor of the Colombian botanist Dairon Cárdenas López, a great collector and connoisseur of the Colombian Amazonian flora. It is so far known only from the type localities. The key to the species with calyptrate flowers included in this article allows 43% of the species in the genus Graffenrieda to be recognized, including four Centronia species.