Climate change may outpace the capacity of forests to adapt to rapid environmental changes, leading to the potential for a mismatch between the climate to which a plant population is adapted and climates of the future. However, our ability to predict and mitigate climate change effects on future forest distributions is limited by an incomplete understanding of the basic rules of how genotype x environment interactions influence an organism’s phenotype (e.g. functional responses or traits enabling a species to persist in a certain climate). Intraspecific, or within-species, variation in functional responses to the environment enables a species to persist in a wide range of climates. Within-species variation can occur via phenotypic plasticity and genetic or ecotypic differentiation. Examination of phenotypic plasticity and genetic differentiation elucidates how the environment x genetic interaction influences species distributions including its size, the direction of distributional shifts, and identification of populations most vulnerable to future climates. Including such intraspecific variation in predictive models would improve predictions of species distributions under future climates. A major limitation is the lack of data from common garden studies. This session promotes research on common garden and reciprocal transplant studies examining the effects of the interaction between the environment and genetic differentiation on plant phenotype, specifically ecophysiology and responses to the environment from leaf-level traits to species distributions. Six speakers (Leander Anderegg, Joe Bailey, Beth Roskilly, Anna Schoettle, Duncan Smith, Kristen Waring) will discuss their expertise in this field of research. The goal is to share research and identify successes, opportunities, challenges, and ways forward to promote future research using common gardens and reciprocal transplant study designs to improve our understanding of the effect of the genotype x environment interaction on plant phenotype and species distributions.