Linking Physiology, Genetics and Evolutionary Ecology in Plant Responses to Global Change.

Current rapid shifts in climate and biogeochemistry are concomitantly shifting the plant attributes most important for plant survival and yield. In evolutionary ecology terms, these attributes are the foci of selection. Can we predict how the foci of selection shift with global change? Our approach has been to hypothesize that there are two major categories of environmental variation that determine the foci of selection. First is the inevitable mis-match between the stoichiometry of resource supply vs. the stoichiometry of resource demand. As the limiting resources change, the foci of selection are predicted to change. We focus on two resources whose supply rate is known to be increasing due to human activities, carbon and nitrogen. We report results of a study of plant trait integration, showing that selection shifts from traits associated with carbon assimilation to traits associated with water and nitrogen use across a gradient of CO2 supply rates from pre-industrial to late 21st century. Across a N supply gradient, we use structural equation modeling and QTL analysis on recombinant inbred lines to show how both the traits under strong selection and the major genes associated with them shift across the gradient. A second source of selection results from abiotic stresses. As the world warms, thermal stress will become an increasingly important limit to native plant distributions and agricultural productivity. We explore genetic variation in the expression of a heat shock protein, AtHsp10, showing that ecotypes from low latitudes express less Hsp101 than more northern ecotypes. We also show that Hsp101 expression suppresses root growth and transpiration rates, suggesting a pleiotropic effect on drought tolerance that may explain the latitudinal gradient in Hsp101 expression. Current work calibrates responses to the characteristics of the native habitat and further characterizes genetic architecture.