Phylogenetic relationships among Strobilanthes s.l. (Acanthaceae): evidence from ITS nrDNA, trnL-F cpDNA, and morphology

Chloroplast trnL-F sequence data, nuclear ribosomal internal transcribed spacer (ITS) sequence data, and morphology were used to analyze phylogenetic relationships among members of the subtribe Strobilanthinae. Parsimony and maximum likelihood analyses of trnL-F indicate that the Strobilanthinae are a monophyletic group. While parsimony analysis of ITS recovers a nonmonophyletic subtribe, maximum likelihood analysis of ITS corroborates results from trnL-F and suggests that systematic error is impacting on ITS parsimony analysis. A combined ITS and trnL-F analysis strengthens the signal and also recovers a monophyletic subtribe. All analyses indicate that Hemigraphis, Sericocalyx, and Strobilanthes are nonmonophyletic. With one exception, all morphological characters included in a combined ITS and morphological analysis are homoplastic. The prospect for a new informative generic classification of the Strobilanthinae aiming to recognize and diagnose only monophyletic groups is considered. While some groups can be diagnosed, adequate diagnosis of the majority of groups remains problematic. Consequently, a single expanded genus Strobilanthes sensu lato is proposed at the level of the well-supported and monophyletic Strobilanthinae.