The Tetramerium lineage (Acanthaceae, Justicieae) revisited: phylogenetic relationships reveal polyphyly of many new world genera accompanied by rampant evolution of floral morphology

Molecular data confirm monophyly of the Tetramerium lineage (Acanthaceae, Justicieae), a group of nearly 200 species, ca. 75% from the New World (NW) and the remainder from Asia or Africa. Compared to our earlier work, > 50% more in-group taxa were sampled (nearly 2/3 of known taxa now sampled) and added ~20% more sequence data. We time-calibrate the phylogeny using primary fossil evidence and the larger context of a calibrated phylogeny for Acanthaceae. Many aspects of relationship are strongly supported but uncertainty remains about a number of phylogenetically isolated taxa (e.g., African Angkalanthus, Chorisochora; NW Ancistranthus) and some aspects of relationships among clades remain weakly supported. The group originated in the OW and began diversifying about 11.5 Ma. A single dispersal event to the NW occurred about 8.3 Ma, likely from Africa to southwestern North America. A number of major clades, particularly in the NW, are less than 5 Ma old and species in many clades are ...