Polyphyly of Rulingia and Commersonia (Lasiopetaleae, Malvaceae s.l.)

The primarily Australian genera Rulingia R.Br. and Commersonia J.R. and G.Forst., as currently circumscribed, are distinguished from each other by the number of antisepalous staminodes. Although most taxonomic treatments recognise Rulingia and Commersonia as separate genera, recent phylogenetic analyses and morphological observations have suggested that neither is monophyletic. In the present study, we test the monophyly of both genera with a phylogenetic analysis of 80 individuals of Rulingia and Commersonia, representing 46 species, using three chloroplast markers. Our analyses recovered the following two well supported clades: Clade 1 includes three species referable to Commersonia and 17 to Rulingia and Clade 2 includes 20 species referable to Commersonia and six to Rulingia. Type species of both Commersonia and Rulingia are in Clade 1, although Commersonia has priority. These results are used to identify lineages that will be formally recognised in accompanying taxonomic treatments. The extensive polyphyly of both Commersonia and Rulingia suggests that the staminode character previously used to separate these two genera is highly homoplastic. We discuss alternative androecial characters that may prove to be synapomorphies for Clades 1 and 2.