Supplementary data are available online at https://academic.oup.com/aob and consist of the following: Table S1: Summary statistics of Experiment 1, Table S2: Summary statistics of Experiment 2, Table S3: Summary statistics of Experiment 3, Fig. S1: Illustration of experimental setup, Fig. S2 Norm of reaction plots and effect size plots illustrating treatment effects on phytochemistry in Experiment 2, Fig. S3 Norm of reaction plots and effect size plots illustrating treatment effects on leaf physiological traits in Experiment 2, Fig. S4 Levels of net photosynthesis rates (raw data) plotted against predawn leaf water potentials, Fig. S5 Stomatal conductance drought response curves, Fig. S6 Norm of reaction plots and effect size plots illustrating treatment effects on growth traits in Experiment 3.

This work was supported by the Swiss National Science Foundation [P2BEP3_175254] and USDA National Institute of Food and Agriculture gransts 2016-67013-25088 and WIS01651. Participation of coauthor KM was supported by the Utah Agricultural Experiment Station, and this is UAES publication #9516.  

We thank Chris Cole, Jack Schaefer, Allyson Richins, Andrew Helm and the Walnut street greenhouse staff for help with setting up the experiments, Mark Zierden for assistance with the chemical analyses, Rick Jellen for cytotype identification and Rebecca Best for advice regarding statistical analyses.