A new species with revolute basal leaf margins of Allomaieta (Melastomataceae, Cyphostyleae) from Colombia

Background and Aims: Allomaieta (Melastomataceae, Cyphostyleae) is a genus of small trees and shrubs endemic to Colombia. Field explorations conducted between 2022 and 2025 in the eastern region of the department Caldas revealed specimens with unique basal revolute leaf margins. The aim of this study is to describe and illustrate Allomaieta basirevoluta sp. nov. from the Central Cordillera of the Colombian Andes, and discuss its taxonomic affinities, ecology, phenology, and conservation status. Methods: Field collections were carried out near the Selva de Florencia National Natural Park. Herbarium collections and relevant taxonomic literature were reviewed. Morphological structures were measured from dried and ethanol-preserved specimens. Its conservation status was evaluated following IUCN Red List criteria. Key results: Allomaieta basirevoluta is described as a new species known from the departments Caldas and Antioquia at elevations between 500 and 1000 m. It represents the first species within the tribe Cyphostyleae known to possess margin domatia. It is morphologically similar to A. javierbarrigae, from which it differs in its margin domatia and white petals, and to the white-flowered A. zenufanasana and A. ebejicosana, from which it differs in its sparsely strigose indumentum, simple dichasia with 3-5 flowers, and larger petals. Known from only two localities outside protected areas, the species is provisionally assessed as Endangered (EN) criterion B1ab(ii,iii,v)+2ab(ii,iii,v). Conclusions: Allomaieta basirevoluta expands the known diversity of the genus to 14 species. The discovery of A. basirevoluta in unprotected forest remnants near Selva de Florencia National Natural Park highlights the conservation value of the lowland humid forests of the Magdalena valley in Caldas, where expanding livestock farming threatens the endemic flora.