Results/Conclusions Studies will be highlighted that aim to determine the primary evolutionary mechanisms that alter plant responses to climate change factors. For example, we have shown that elevated CO2 can influence the expression of floral initiation genes in Arabidopsis thaliana, and such effects may cause unexpected developmental disruptions that ultimately influence plant productivity. We have also shown that white ash trees are adapted to differences in water availability across their native range, and that these genetic differences among trees largely influence their responses to drier climates predicted for the future. Finally, we show carbon isotope data illustrating the physiological responses of juniper trees from the last ice age through the present, providing an example of how physiological responses of trees to past climates may inform our future predictions of plant responses to anthropogenic changes. Taken together, this talk will highlight our need to incorporate evolutionary responses of plants into future climate change scenarios, and will emphasize the need to better understand the primary physiological and evolutionary mechanisms that may produce unexpected responses of plants in the future.