The genus Oxalis has 500 species occurring in America and Africa. It is divided into four subgenera and 28 sections, of which the subgenus Thamnoxys (Endl.) Progel with nine sections and 71 species, and is distinguished by morphological complexity. In order to understand the phylogenetic relationships of section Thamnoxys and with other sections of the subgenus, we carried out a cladistic analysis based on morphological characters. A total of 28 taxa were included and 72 morphological characters were considered. The analysis showed 673 equally parsimonious trees with 274 steps. In the consensus tree was observed the formation of the monophyletic group Oxalis subgen. Thamnoxys and no bulbs as synapomorphies, petioles up to 10 cm long, pinnate leaves (presence of leaf rachis), peduncle less than 7 cm long, pedicel up to 1 cm and the absence of glands at the apex of the sepals. Oxalis sect. Thamnoxys presented polyphyletic taxon and the inclusion of other sections within O. sect. Thamnoxys will constitute it as monophyletic group. We suggest considering the subgenus Thamnoxys no subdivisions as it emerged with high boostrap support.
Brazil; phylogeny; morphology; Oxalidales
