1Present address: Center for Tropical Forest Science, Smithsonian Tropical Research Institute, Apartado Postal 0843-03092, Panamá, Panama.
The age of the grasses and clusters of origins of C4 photosynthesis
Article first published online: 28 OCT 2008
© 2008 The Authors. Journal compilation © 2008 Blackwell Publishing Ltd
Global Change Biology
Volume 14, Issue 12, pages 2963–2977, December 2008
How to Cite
VICENTINI, A., BARBER, J. C., ALISCIONI, S. S., GIUSSANI, L. M. and KELLOGG, E. A. (2008), The age of the grasses and clusters of origins of C4 photosynthesis. Global Change Biology, 14: 2963–2977. doi: 10.1111/j.1365-2486.2008.01688.x
- Issue published online: 18 NOV 2008
- Article first published online: 28 OCT 2008
- Received 23 April 2008 and accepted 27 May 2008
- Miocene climate;
At high temperatures and relatively low CO2 concentrations, plants can most efficiently fix carbon to form carbohydrates through C4 photosynthesis rather than through the ancestral and more widespread C3 pathway. Because most C4 plants are grasses, studies of the origin of C4 are intimately tied to studies of the origin of the grasses. We present here a phylogeny of the grass family, based on nuclear and chloroplast genes, and calibrated with six fossils. We find that the earliest origins of C4 likely occurred about 32 million years ago (Ma) in the Oligocene, coinciding with a reduction in global CO2 levels. After the initial appearance of C4 species, photosynthetic pathway changed at least 15 more times; we estimate nine total origins of C4 from C3 ancestors, at least two changes of C4 subtype, and five reversals to C3. We find a cluster of C4 to C3 reversals in the Early Miocene correlating with a drop in global temperatures, and a subsequent cluster of C4 origins in the Mid-Miocene, correlating with the rise in temperature at the Mid-Miocene climatic optimum. In the process of dating the origins of C4, we were also able to provide estimated times for other major events in grass evolution. We find that the common ancestor of the grasses (the crown node) originated in the upper Cretaceous. The common ancestor of maize and rice lived at 52 ± 8 Ma.