Phylogenetics, Morphology, and Evolution of the Large Genus<i>Myrcia</i>s.l. (Myrtaceae)

Phylogenetic relationships of Myrcia s.l., the most species-rich tree genus in the Brazilian cerrado and Atlantic forests, are reconstructed by analysis, with parsimony and Bayesian inference, of four plastid regions (psbA-trnH intergenic spacer, trnL intron, trnL-F intergenic spacer, and matK exon) and the external and internal transcribed spacer regions of nuclear ribosomal DNA. The resulting phylogenetic hypothesis is evaluated in conjunction with key morphological characters and abiotic factors suggested to have influenced the group’s current distribution. Some lineages identified by previous classifications are supported; others with morphological and/or ecological correspondence are recognized for the first time. Sequence divergence levels provide good resolution of relationships within but not between the main clades of Myrcia s.l. The previously recognized genera Calyptranthes and Gomidesia are shown to be monophyletic, whereas Marlierea is shown not to be; all are nested within paraphyletic Myrcia. A new subgeneric classification is required. An interpretation of the origins of Myrcia s.l. and potential causes of speciation in the group is made on the basis of recently published data and accepted geological events.