title: Phylogenetic relationships of Aristida and relatives (Poaceae, Aristidoideae) based on noncoding chloroplast (trnL-F, rpl16) and nuclear (ITS) DNA sequences.
abstract: OBJECTIVE
  The cosmopolitan and ecologically important grass subfamily Aristidoideae comprises the widely distributed genus Aristida (250-290 species), Stipagrostis (50 species, with an African-Asian distribution), and Sartidia (five species, Africa and Madagascar). The subfamily includes species with C(3) (Sartidia and a single species of Aristida) and C(4) photosynthetic pathways. Rigorous phylogenetic reconstructions of species relationships are required to explain the biogeographic, physiological, and ecological diversity within this subfamily.
  
  
  METHODS
  Chloroplast (trnL-F, rpl16) and nuclear (ITS) DNA sequences were obtained from 198 accessions, and the combined data set was subjected to parsimony, maximum likelihood, and Bayesian inference analyses. Dating analyses calibrated using previously published node ages were conducted to determine the ages of major radiations.
  
  
  RESULTS
  The C(3) Sartidia is sister to a monophyletic Stipagrostis, and the (Sartidia, Stipagrostis) clade is sister to Aristida. Within Aristida, the only known C(3) species, A. longifolia, is sister to the remainder of the genus. Infrageneric sections of Aristida were not supported, and there are no synapomorphic morphological characters for the clades retrieved. Within Aristida, monophyletic Australian, African, North American, and South American clades are retrieved.
  
  
  CONCLUSIONS
  The subfamily dates back to the late Miocene, with the major lineages present by the Pliocene. With one exception, regional clades of Aristida evolved in the Pliocene. The C(3) photosynthetic pathway is hypothesized to be the pleisomorphic condition for the subfamily, wherein two independent C(4) pathways (each with unique anatomical and genetic features) evolved, one within Aristida and one in Stipagrostis.
authors: Rancho Santa Ana Botanic Garden and Claremont Graduate University, 1500 North College Avenue, Claremont, California 91711-3157, USA. tlatilpa@uaem.mx
authors: Rosa
authors: R
authors: Cerros-Tlatilpa
authors: J Travis
authors: JT
authors: Columbus
authors: Nigel P
authors: NP
authors: Barker
mesh_terms: D000349:Africa; D001315:Australia; D001483:Base Sequence; D002736:Chloroplasts / Q000235:genetics; D018742:DNA, Chloroplast; D019143:Evolution, Molecular; D014644:Genetic Variation; D005843:Geography; D009656:North America; D010802:Phylogeny; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000145:classification*; D006109:Poaceae / Q000145:classification* / Q000235:genetics*; D013020:South America
chemical_list: D018742:DNA, Chloroplast