Phylogenetic relationships in the myrmecophytic genus Tococa (Melastomataceae) were investigated using morphological data. The data matrix comprised 42 ingroup taxa, two of them previously described as Microphysca, the monotypic genus Myrmidone, and 11 species of the genus Miconia as outgroups. Vegetative and floral characters were used, in addition to characters drawn from seeds using both light and electron microscopy. A cladistic analysis of the morphological matrix, containing 58 informative characters, resulted in 224 most parsimonious trees. This analysis shows that Tococa is not monophyletic, both because there are some species of Tococa more closely related to Miconia than to the remaining species of Tococa, and because Myrmidone and Microphysca are nested within Tococa. However, it is possible to recognize a large, well-supported clade that includes Myrmidone and most species of Tococa. This clade is here defined as Tococa sensu stricto. The tooth in the dorsal side of the anther connective that has been informally proposed in the past as a synapomorphy for Tococa, although present in most species of Tococa sensu stricto, is not a synapomorphy for the genus. Synapomorphies for Tococa sensu stricto include the presence of emarginate petals, truncate ovaries and straight anticlinal walls in the cells of the seed testa. Within Tococa sensu stricto, ant domatia have evolved at least twice, and have been secondarily lost at least once.

Communicating Editor: Kathleen A. Kron