Disentangling the infrageneric classification of megadiverse taxa from Mata Atlantica: Phylogeny of Miconia section Chaenanthera (Melastomataceae: Miconieae)

摘要

Miconia is the largest genus restricted to the Neotropics, with about 1060 species, and one of the biggest in Mata Atlantica, with 115 species. As currently defined, Miconia is clearly polyphyletic with no clear boundaries to the other genera in the Miconieae. Moreover, the traditional infrageneric classification does not reflect the evolutionary history of the group, thus limiting its utility for identification and monographic purposes. Miconia sect. Chaenanthera and M. sect. Jucunda are two sections mostly restricted to Mata Atlantica that have previously been shown to belong to a single clade (Chaenanthera clade), despite being morphologically distinct from each other. In this paper, we provide a new phylogenetic hypothesis for the Chaenanthera clade with an expanded sampling of both taxa and molecular markers, in order to provide a base for future taxonomic studies. Given the incongruent patterns observed across different markers in our preliminary analyses, a phylogenetic network was also estimated for the group. The history of some morphological characters was reconstructed and the phylogenetic position of a few molecularly unsampled species was estimated based on their morphology. The Chaenanthera clade was corroborated with strong support, although resolution is still unsatisfactory for several relationships within the group. Individual flower-related characters do not reliably predict phylogenetic relationships in this group. Morphological diagnostic characters for above species taxa will demand character combinations and likely the inclusion of other sources of information. We also present the first line of evidence supporting the presence of reticulation shaping the history of the Chaenanthera clade. The concerted effect of incongruent signal, limited variability, incomplete lineage sorting and reticulation events, is certainly a major force driving the phylogenetic support recovered in our analyses, and likely in several other published trees across Melastomataceae.