A revision of Pterolepis (Melastomataceae: Melastomeae)

Pterolepis consists of herbs and small shrubs with pink, purple, or white (3‐)4–5‐merous flowers, stamens with basal‐ventrally prolonged connectives, and cochleate seeds. The majority of the species occur in central Brazilian cerrado vegetation, but two weedy species have become widespread, one ranging from Bolivia to southern Mexico, the other from Paraguay to the West Indies. Pterolepis appears related to the paleotropical genera Osbeckia, Melastoma, and Dissotis and to the neotropical genus Tibouchina. The main diagnostic feature of the genus are branched emergences in the intercalycine sinuses but these are variable among the species and also occur in many paleotropical and two neotropical species, casting some doubt on their taxonomic value above the species level. Within Pterolepis, 14 of the 80 taxa proposed by previous authors are recognized and eight species are illustrated; one new species, P. picorondonica from Amazonian Brazil, and a new variety, P. parnassiifolia var. piatensis from Bahia, are described. Also provided are scanning electron micrographs of the seeds of most, and distribution maps of all species.