Phylogeny of Miconia (Melastomataceae):: Patterns of stamen diversification in a megadiverse Neotropical genus

Phylogenetic relationships within Miconia and other genera in the Neotropical tribe Miconieae were investigated using a maximum parsimony analysis of nuclear internal transcribed spacer and ndhF nucleotide sequences. Included were all sections in Miconia ( 212 species, similar to 20% of the genus) and 12 of the 15 remaining genera assigned to the tribe ( an additional 239 species). Given the tribe's reputation for problematic generic distinctions, it was not surprising that most traditionally recognized taxonomic groups - both genera and sections - were shown to be polyphyletic or paraphyletic. Nevertheless, Miconia is composed of several distinct monophyletic groups, with a large majority of the species belonging to only four clades. Some of these groups represent parts of sections proposed in the last revision of the genus, but most of the diversification seems to have occurred in geographical areas that are more restricted than would have been predicted by the distribution of these sections. Moreover, parallel evolutionary trends are seen in anther form, i.e., shifts from elongate to shorter anthers and from minute-pored to large-pored or slitlike dehiscent anthers. These changes may relate to pollinator shifts, especially from buzz pollination to nonvibrational pollination. Thus, the major evolutionary diversifications within the tribe have been obscured by convergence in stamen morphology, leading to many arbitrary generic and sectional circumscriptions.