An expanded phylogeny of Setaria (Poaceae, Panicoideae, Paniceae) and its relationships within the subtribe Cenchrinae

Abstract

AbstractSetaria P. Beauv. is the largest genus of the “bristle clade”, including between 115 and 160 species. Previous molecular phylogenetic studies showed Setaria likely to be para- or polyphyletic, retrieving several clades apparently consistent in all analyses and correlated with the geographic origin of species. In this study, we evaluate the phylogeny of the subtribe Cenchrinae using parsimony, likelihood, and Bayesian inference based on the plastid marker ndhF and increasing the number of sampled species. Our main objective was analyze American taxa with inflorescences of the “Paspalidium type” (i.e., subgenera Paurochaetium and Reverchoniae) to test whether they, as traditionally circumscribed, form a natural group. Our findings recovered both subgenera as polyphyletic, with their species distributed in different morphologically distinctive clades and not necessarily correlated with the geographic origin. Additionally, we were able to include a second voucher of species that were imprecisely located in previous studies and define their placements in the tree, as well as confirm that Setaria is polyphyletic as currently delineated. A comparison with the results from other studies, comments on Stenotaphrum Trin. and a brief discussion on conflicting placements in the “Cenchrus clade”, and of Acritochaete Pilg. are also included here.