A phylogeny of the Cotteinae (Poaceae, Chloridoideae, Eragrostideae)

To investigate the evolutionary relationships among 23 species in the Cotteinae we generated a DNA sequence-derived phylogeny utilizing three plastid (rps16-trnK spacer, rps16 intron, rpl32-trnL spacer) regions and the nuclear ribosomal internal transcribed spacer (ITS) region. The Bayesian tree provides strong support for the monophyly of the Cotteinae and its four genera, in order of divergence: Cottea, the Kaokochloa + Schmidtia clade, and the Enneapogon clade. Since the Eragrostideae clearly evolved from African ancestors and Kaokochloa, Schmidtia, and Enneapogon all share species from Africa, we hypothesize the ancestral area of Cotteinae to be Africa. Within Enneapogon we recovered four major clades, the first two splits with species primarily from Africa and the third split containing a basal species from Africa/Asia/Europe sister to all species from Australia. The ancestral area of Enneapogon is Africa and based on our current sample the 13 species from Australia appear to be derived from a single dispersal event from an ancestor shared with E. persicus.