Intraspecific variation in plant responses to atmospheric CO2, temperature, and water availability

In this chapter we compile data on intraspecifc variation in plant reproductive, growth, and physiological responses to changes in atmospheric CO2, temperature, and water availability. In total, we extracted data from 71 studies comprising a total of 79 species representing all major growth forms, functional groups, and biomes. Cumulatively, these studies examined responses to environmental change in 1154 genotypes. We used these data to examine: (1) the extent to which natural populations and genotypes within species vary in their response to increasing CO2, warmer temperatures, and reduced water availability, and (2) whether intraspecifc variation in these responses differs among growth forms, functional groups, biomes, and the phenotypic trait. In general, genotypes or populations of many species showed a wide range of responses to elevated CO2, warming, and reduced water availability. However, probability values (p-values) for genotype-by-environment interaction terms (usually from analysis of variance) varied from 0.90 depending upon the study design (and species), the environmental factor, and the scale of the trait. More studies reported significant intraspecifc variation in plant responses to increasing temperature and decreasing water availability than intraspecifc variation in plant responses to increasing CO2. Thus, warmer and drier conditions may be more likely to result in evolutionary changes within species than increasing CO2 alone. We also find that intraspecifc variation in plant responses to environmental change is generally higher for reproductive and growth traits than for leaf-scale physiological traits. Even so, moderate intraspecifc variation in physiological responses could result in substantial variation in growth and reproductive responses among genotypes. We conclude by discussing our understanding of genetic features that influence genotype-by-environment interactions. We go on to identify future research directions for advancing our understanding of the causes and consequences of intraspecifc variation in plant responses to global change