A Taxonomic Revision of the Marlierea Clade (Myrcia sect. Aulomyrcia, Myrtaceae)

A taxonomic revision of the 20 species of the Marlierea clade (Myrcia DC. sect. Aulomyrcia (O. Berg) Griseb., Myrtaceae) is presented, including an identification key to the species, morphological descriptions, IUCN conservation risk assessments, and notes. While this lineage cannot be assigned a Linnean taxonomic rank until relationships in Myrcia are better resolved, it is here described for the first time. The species in the Marlierea clade are found in forests, sandy vegetation, and rocky outcrops along the Atlantic domain and the Espinhaço Mountains in Brazil. Myrcia botryoidea Gaem & Mazine, M. multipaniculata Gaem & Mazine, and M. regia Gaem & E. Lucas are described as species new to science. Nine new synonyms are proposed: Marlierea excoriata Mart. var. angustifolia O. Berg and Marlierea suaveolens Cambess. under Myrcia excoriata (Mart.) E. Lucas & C. E. Wilson; Marlierea estrellensis O. Berg, Marlierea glabra Cambess. var. gracilis O. Berg, and Marlierea grandifolia O. Berg var. minor O. Berg under Myrcia neoglabra E. Lucas & C. E. Wilson; Myrtus rufa Vell. under Myrcia neoobscura E. Lucas & C. E. Wilson; Eugeniopsis riedeliana O. Berg and Marlierea spathulata O. Berg under Myrcia neotomentosa E. Lucas & C. E. Wilson; and Calyptranthes langsdorffii O. Berg var. macrophylla Kiaersk. under Myrcia parviflora (O. Berg) Gaem & E. Lucas. Additionally, six lectotypes and one epitype are proposed. Eleven species are currently under risk of extinction, emphasizing the need for conservation initiatives targeted to the distribution areas of this group. The present work poses a major change in the systematics of the Marlierea clade, demonstrating that species of relatively well-explored tropical floras, such as the Atlantic Forest, remain understudied.