Taxonomic notes in Myrcia sect. Gomidesia (Myrtaceae) from Rio de Janeiro, Brazil: reestablishment of M. dolichopetala, and a new species, M. macrobracteosa

This study was conducted in the context of a taxonomic treatment for Myrcia species occurring in the Brazilian state of Rio de Janeiro. While revising current synonyms of endemic species of Myrcia sect. Gomidesia, we found consistent morphological separation between Myrcia gestasiana and Myrcia dolichopetala, presently treated as synonyms and detached here. Individuals co-occurring with M. dolichopetala are here recognized and described as a new species, Myrcia macrobracteosa, the specific epithet being allusive of its unusually showy, persistent and accrescent bracts and bracteoles. A taxonomic treatment is provided for each species based on herbarium collections and field data, and their diagnostic characters are contrasted in a comparative table. Morphological plates of fresh and dry material are also provided with notes on taxonomy and distribution, including a map of occurrence records. The three taxa occur in urban forest remnants under extreme threat in the Rio de Janeiro Metropolitan Region. In this context, preliminary conservation assessments are also provided for each species based on occurrence data from herbaria and field information.