Graduate Fellow

Origins of the C4 grassland system: phylogenetic biome assembly

PI(s): Daniel Griffith (Wake Forest University (Winston-Salem,NC))
Start Date: 18-Jan-2012
End Date: 25-Mar-2012
Keywords: phylogenetics, macroevolution, adaptive radiation, community ecology, database

In the late Miocene and Pliocene tropical and subtropical grassland communities rapidly transitioned from species that use the ancestral C3 ¬photosynthesis pathway to those dominated by C4 grasses adapted to high light and high temperature. The explosive radiation and expansion of C4 grasses resulted in the formation of a new biome dominated numerically by relatively few abundant species drawn from a much larger pool of less abundant species. In fact, only around 600 of the 12,000 extant Poaceae might be considered to be dominant grassland species, and these species appear to cluster phylogenetically1. The propensity of these specific lineages to become dominant strongly suggests that there are traits other than C4 photosynthesis that confer dominance in grasslands and that those traits were causally linked to C4 grassland origins. A primary question becomes: why do certain species dominate, and are there scale-independent environmental determinants of dominance? I propose a synthesis of existing grassland plot data linked to phylogeny, plant trait data, and local environmental conditions with the goal of comparing the dominant species niche at “ecoregion”2 and intra-ecoregion scales across 4 continents. The aims of the proposed project strongly complement those of the “C4 grasslands” working group, and I will contribute to this group’s work.