Frostburg, Md. (November 15, 2010) A new analysis of fossilized grass-pollen grains deposited on ancient European lake and sea bottoms 16-35 million years ago reveals that C4 grasses evolved earlier than previously thought. This new evidence casts doubt on the widely-held belief that the rise of this incredibly productive group of plants was driven by a large drop in atmospheric carbon dioxide concentrations during the Oligocene epoch.
The research team, led by University of Maryland Center for Environmental Science Appalachian Laboratory researcher Dr. David Nelson and University of Illinois Professor Feng Sheng Hu, examined the carbon isotope signatures of hundreds of grass-pollen grains and found that C4 grasses were already present on the landscape during the early part of the Oligocene, some 14 million years earlier than previously thought from geological evidence. Their findings are now published online in the journal Geology and will shortly appear in the print edition.
"The idea that C4 grasses originated prior to global decreases in carbon dioxide levels requires us to reevaluate the way we think about the evolution of C4 photosynthesis," said Dr. Nelson. "This new information should encourage the examination of alternate evolutionary selection pressures, such as warm temperatures or dry climates."
C4 plants compose only 3 percent of flowering plant species, yet account for about 25 percent global terrestrial productivity. About 60% of C4 species are grasses, and they dominate the world's grassland and savanna biomes, particularly those in warmer, lower latitude areas. Their ecological success results from the way these species concentrate and then fix carbon dioxide in order to power photosynthesis. While the most well known C4 plants are maize and sugar cane, both of which are critical to human consumption, there is a growing interest in their use as biofuels in order to capture carbon from the atmosphere to mitiga
|Contact: Christopher Conner|
University of Maryland Center for Environmental Science