title: Diversification of C(4) grasses (Poaceae) does not coincide with their ecological dominance.
abstract: OBJECTIVE
  The radiation of a lineage and its rise to ecological dominance are distinct phenomena and driven by different processes. For example, paleoecological data has been used to show that the Cretaceous angiosperm radiation did not coincide with their rise to dominance. Using a phylogenetic approach, we here explored the evolution of C4 grasses and evaluated whether the diversification of this group and its rise to ecological dominance in the late Miocene were decoupled.
  
  
  METHODS
  We assembled a matrix including 675 grass species of the PACMAD clade and 2784 characters (ITS and ndhF) to run a molecular dating analysis using three fossils as reference calibrations. We coded species as C3 vs. C4 and reconstructed ancestral states under maximum likelihood. We used the program BiSSE to test whether rates of diversification are correlated with photosynthetic pathway and whether the radiation of C4 lineages preceded or coincided with their rise to ecological dominance from ∼10 Ma.
  
  
  RESULTS
  C4 grass lineages first originated around 35 Ma at the time of the Eocene-Oligocene transition. Accelerated diversification of C4 lineages did not coincide with their rise to ecological dominance.
  
  
  CONCLUSIONS
  C4-dominated grasslands have expanded only since the Late Miocene and Pliocene. The initial diversification of their biotic elements can be tracked back as far as the Eocene-Oligocene transition. We suggest that shifts in taxonomic diversification and ecological dominance were stimulated by different factors, as in the case of the early angiosperms in the Cretaceous.
authors: Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa.
authors: Yanis
authors: Y
authors: Bouchenak-Khelladi
authors: Jasper A
authors: JA
authors: Slingsby
authors: G Anthony
authors: GA
authors: Verboom
authors: William J
authors: WJ
authors: Bond
mesh_terms: D005075:Biological Evolution; D004463:Ecology; D017753:Ecosystem; D005580:Fossils; D014644:Genetic Variation; D010788:Photosynthesis / Q000235:genetics*; D010802:Phylogeny; D063148:Plant Dispersal; D006109:Poaceae / Q000235:genetics*
keywords: angiosperms; dating; diversification; ecological dominance; evolutionary history; grasses (Poaceae); phylogenetics