PHYLOGENETICS OF ANDROPOGONEAE (POACEAE: PANICOIDEAE) BASED ON NUCLEAR RIBOSOMAL INTERNAL TRANSCRIBED SPACER AND CHLOROPLAST trnL-F SEQUENCES

Phylogenetic relationships among 85 species representing 35 genera in the grass tribe Andropogoneae were estimated from maximum parsimony and Bayesian analyses of nuclear ITS and chloroplast trnL-F DNA sequences. Ten of the 11 subtribes recognized by Clayton and Renvoize (1986) were sampled. Independent analyses of ITS and trnL-F yielded mostly congruent, though not well resolved, topologies. Arundinella is sister to Andropogoneae in the trnL-F phylogeny and is nested within the tribe in the ITS and combined data trees. Tristachya is sister to Andropogoneae + Arundinella in the ITS phylogeny. Four clades are common to the ITS and trnL-F phylogenies and the trees from the combined data set. Clade A consists of Andrapogon, Diectomis, Hyparrhenia, Hyperthelia, and Schizachyrium. Within this clade, Andropogon distachyos, Hyparrhenia, and Hyperthelia form clade C. Clade B consists of Bothriochloa, Capillipedium, and Dichanthium, and clade D includes Chrysopogon and Vetiveria. Analysis of the combined data resulted in an unsupported larger clade comprising clades A and B plus Cymbopogon, and a sister clade of Heteropogon, Iseilema, and Themedu. This larger clade is similar to the core Andropogoneae clade previously reported (Spangler et al. 1999; Mathews et al. 2002). Based on our sample, which represents 41% of the tribe's genera, most of Clayton and Renvoize's (1986) subtribes are not monophyletic.