Phylogenetic analysis of the Briza Complex (Poaceae)

A phylogenetic analysis of the Briza Complex was carried out using three DNA regions (ITS, GBSSI and trnL-trnL-trnF, a total of 2980bp). The searches were performed by three distinct phylogenetic methods, using plastid and nuclear data in separate matrices. All methods produced similar trees per matrix. However there were conflicts when trees resulting from distinct datasets were compared. Phylogenetic relationships were found did not completely fit any circumscription previously proposed for the complex. The early divergence of the Eurasiatic species (B. media, B. maxima and B. minor), and the monophyly of the South American group (including Erianthecium, Rhombolytrum and Gymnachne) support Briza L. sensu stricto, and a single genus for the American group. Briza sensu lato is not supported in most trees, and the American genera cannot be split due to unresolved polytomies. Conflict between chloroplast and nuclear data suggests past reticulation events, although lineage sorting or ITS paralogy cannot be ruled out. Polytomies in the American group may indicate rapid species radiation.