Figure 1.

Possible outcomes of a reciprocal transplant experiment showing the expected effect of different mechanisms of evolutionary change. Solid grey line is ambient CO₂ selection line; dashed black line is elevated CO₂ selection line. (a) Beneficial mutations in elevated CO₂ lines could lead to specific adaptation to elevated CO₂. (b) Conditionally deleterious mutations in genes regulating carbon uptake and efficient use could accumulate at elevated CO₂, lowering fitness of high lines in ambient CO₂. (c) A trade-off in adapting to elevated CO₂ or a combination of specific response and conditionally deleterious mutation could lead to lines from each environment becoming adapted only to their environment. (d) Our selection lines might diverge due to factors not directly related to CO₂.