Leaf morphology and anatomy in Myrcia sect. Aulomyrcia (Myrtaceae): species circumscription and characterization of clades

Myrcia DC., a diverse neotropical genus of Myrtaceae, encompasses 793 species. However, species of Myrcia are similar and difficult to distinguish. In Myrcia sect. Aulomyrcia (O. Berg) Griseb., leaf features help distinguishing clades and species. Our aim is to provide leaf data for species of M. sect. Aulomyrcia's clades F and G. We sampled 31 specimens of 13 species of Myrcia sect. Myrcia subobliqua (Benth.) Nied., and Myrcia tetraphylla Sobral). Samples were subjected to sectioning and staining techniques for morphological and anatomical analysis through stereo and light microscopy. Leaf blade and petiole morphological and anatomical features were described carefully for the first time for these 13 species. We provided an identification key based on leaf features. Our findings are discussed in the light of Myrcia sect. Aulomyrcia systematics. We comment of the significance of petiolar and blade features, such as trichomes types and location, phyllotaxis, rhytidome peeling, periderm and lenticels, and petiole, blade, and vascular cylinder shape. Our study brings novel information on leaf structure variation in Myrcia sect. Aulomyrcia, delivering much needed data for species and clades circumscription and identification.