Phylogenetic relationships and distribution of New World Melastomeae (Melastomataceae)

In this study we present a phylogenetic analysis of Melastomeae, focusing on the Neotropical members of the tribe, a group of c. 70 species in 30 genera. In total, 236 species, including outgroups (Miconieae and Merianieae) and representatives of the Microlicieae and Rhexieae, were sequenced for the nuclear ribosomal internal transcribed spacer (nrITS), and the plastid spacers accD-psaI and psbK-psbL. Melastomeae are not resolved as monophyletic because a group of mostly herbs and small trees with mostly tetramerous flowers (Acanthella, Aciotis, Acisanthera, Appendicularia, Comolia, Ernestia, Fritzschia, Marcetia, Macairea, Nepsera, Sandemania and Siphanthera) is nested between Rhexieae and Microlicieae. The remaining New World Melastomeae are not resolved as monophyletic, because a group of Old World genera (Osbeckia, Melastoma, Tristemma and allied genera) are nested in the tribe. The large genus Tibouchina is not monophyletic because Brachyotum, Bucquetia, Castratella, Centradenia, Chaetolepis, Heterocentron, Itatiaia, Microlepis, Monochaetum, Pilocosta, Svitramia, and Tibouchinopsis are nested in it, even although all of these genera are recovered as monophyletic. Each major clade has remarkable habitat and geographical integrity. The clade formed by Tibouchina and allies appears to have arisen in savannas in lowland South America and later expanded to forest, campo and high Andean biomes. At least two groups have radiated in eastern Brazil, and two other groups in the Andes and mountains of Central America. Niche conservatism and colonization of adjacent environments seem to have driven speciation in Neotropical Melastomeae.