Species interactions in a changing environment : elevated CO2 alters the ecological and potential evolutionary consequences of competition

Question: How will global changes impact the ecological and evolutionary outcomes of competition? Hypothesis: Global changes that alter resource availability, such as rising atmospheric CO2 concentrations, will alter the effects of competition on mean fitness and patterns of natural selection. Because species exhibit different growth responses to elevated CO2 and because different traits may aid in competition against different taxa, these ecological and evolutionary effects may depend on the identity of the competitor. Organism: Arabidopsis thaliana grown under intraspecific competition or interspecific competition with the C3 grass Bromus inermis or the C4 grass Andropogon gerardii. Field site: BioCON (Biodiversity, CO2, and Nitrogen) experiment at Cedar Creek Ecosystem Science Reserve, Minnesota, USA. Methods: Manipulate the presence and type of competition experienced by A. thaliana populations growing under ambient or elevated CO2 conditions. Measure the interactive effects of CO2 and competition on mean fitness and on patterns of natural selection. Conclusions: Elevated CO2 reduces the effects of competition on mean fitness, alters the relative fitness effects of different competition treatments, and minimizes the strength of competition as a selective agent.