The origins of C4 grasslands: integrating evolutionary and ecosystem science

The evolution of grasses using C4 photosynthesis and their sudden rise to ecological dominance 3 to 8 million years ago is among the most dramatic examples of biome assembly in the geological record. A growing body of work suggests that the patterns and drivers of C4 grassland expansion were considerably more complex than originally assumed. Previous research has benefited substantially from dialog between geologists and ecologists, but current research must now integrate fully with phylogenetics. A synthesis of grass evolutionary biology with grassland ecosystem science will further our knowledge of the evolution of traits that promote dominance in grassland systems and will provide a new context in which to evaluate the relative importance of C4 photosynthesis in transforming ecosystems across large regions of Earth. Photosynthesis is the fundamental biologicalprocess that transforms solar energy into thechemical fuel for life by generating sugars from water and CO2. The ancestral pathway (C3 photosynthesis) evolved in a CO2-rich atmosphere more than 2800million years ago (Ma), but deple-tion of atmospheric CO2 about 30Ma has reduced the efficiency and rate of carbon uptake in man