Phylogenetics of Andropogoneae (Poaceae: Panicoideae) Based on Nuclear Ribosomal Internal Transcribed Spacer and Chloroplast trnL–F Sequences

Abstract

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.