New grass phylogeny resolves deep evolutionary relationships and discovers C4 origins


  • Grass Phylogeny Working Group II

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    • Sandra Aliscioni1, Hester L. Bell2, Guillaume Besnard3,4, Pascal-Antoine Christin5, J. Travis Columbus2, Melvin R. Duvall6, Erika J. Edwards5, Liliana Giussani7, Kristen Hasenstab-Lehman2, Khidir W. Hilu8, Trevor R. Hodkinson9, Amanda L. Ingram10, Elizabeth A. Kellogg11, Saeideh Mashayekhi2, Osvaldo Morrone7, Colin P. Osborne12, Nicolas Salamin13,14, Hanno Schaefer15, Elizabeth Spriggs5, Stephen A. Smith5,16 and Fernando Zuloaga7
      1Cátedra de Botánica Agrícola, Facultad de Agronomía, Universidad de Buenos Aires, Av. San Martín 4453, C1417DSE, Buenos Aires, Argentina; 2Rancho Santa Ana Botanic Garden and Claremont Graduate University, 1500 North College Avenue, Claremont, CA 91711-3157, USA; 3CNRS, UPS, ENFA, Laboratoire Evolution & Diversité Biologique, UMR 5174, 31062 Toulouse 4, France; 4Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot SL5 7PY, UK; 5Department of Ecology and Evolutionary Biology, Brown University, Box G-W, Providence, RI 02912, USA; 6Department of Biological Sciences, Northern Illinois University, 1425 W Lincoln Hwy, DeKalb, IL 60115-2861, USA; 7Instituto de Botánica Darwinion, Labardén 200, Casilla de Correo 22, B1642HYD, San Isidro, Buenos Aires, Argentina; 8Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA; 9Department of Botany, School of Natural Sciences, University of Dublin, Trinity College, Dublin D2, Ireland; 10Department of Biology, Wabash College, PO Box 352, Crawfordsville, IN 47933, USA; 11Department of Biology, University of Missouri-St Louis, St Louis, MO 63121, USA; 12Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK; 13Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland; 14Swiss Institute of Bioinformatics, Quartier Sorge, 1015 Lausanne, Switzerland; 15Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Avenue, Cambridge, MA 02138, USA;16Heidelberg Institute for Theoretical Studies, Heidelberg, Germany.

Author for correspondence:
Erika J. Edwards
Tel: +1 401 863 2081


  • Grasses rank among the world’s most ecologically and economically important plants. Repeated evolution of the C4 syndrome has made photosynthesis highly efficient in many grasses, inspiring intensive efforts to engineer the pathway into C3 crops. However, comparative biology has been of limited use to this endeavor because of uncertainty in the number and phylogenetic placement of C4 origins.
  • We built the most comprehensive and robust molecular phylogeny for grasses to date, expanding sampling efforts of a previous working group from 62 to 531 taxa, emphasizing the C4-rich PACMAD (Panicoideae, Arundinoideae, Chloridoideae, Micrairoideae, Aristidoideae and Danthonioideae) clade. Our final matrix comprises c. 5700 bp and is > 93% complete.
  • For the first time, we present strong support for relationships among all the major grass lineages. Several new C4 lineages are identified, and previously inferred origins confirmed. C3/C4 evolutionary transitions have been highly asymmetrical, with 22–24 inferred origins of the C4 pathway and only one potential reversal.
  • Our backbone tree clarifies major outstanding systematic questions and highlights C3 and C4 sister taxa for comparative studies. Two lineages have emerged as hotbeds of C4 evolution. Future work in these lineages will be instrumental in understanding the evolution of this complex trait.