Scaling up evolutionary responses to elevated CO2:: lessons from Arabidopsis

Results from norm of reaction studies and selection experiments indicate that elevated CO2 will act as a selective agent on natural plant populations, especially for C-3 species that are most sensitive to changes in atmospheric CO2 concentration. Evolutionary responses to CO2 may alter plant physiology, development rate, growth, and reproduction in ways that cannot be predicted from single generation studies. Moreover, ecological and evolutionary changes in plant communities will have a range of consequences at higher spatial scales and may cause substantial deviations from ecosystem level predictions based on short-term responses to elevated CO2. Therefore, steps need to be taken to identify the plant traits that are most likely to evolve at elevated CO2, and to understand how these changes may affect net primary productivity within ecosystems. These processes may range in scale from molecular and physiological changes that occur among genotypes at the individual and population levels, to changes in community- and ecosystem-level productivity that result from the integrative effects of different plant species evolving simultaneously. In this review, we (1) synthesize recent studies investigating the role of atmospheric CO2 as a selective agent on plants, (2) discuss possible control points during plant development that may change in response to selection at elevated CO2 with an emphasis at the primary molecular level, and (3) provide a quantitative framework for scaling the evolutionary effects of CO2 on plants in order to determine changes in community and ecosystem productivity. Furthermore, this review points out that studies integrating the effects of plant evolution in response to elevated CO2 are lacking, and therefore more attention needs be devoted to this issue among the global change research community.