Misinterpreting the adaptive value of phenotypic plasticity in studies on plant adaptation to new and variable environments.

Phenotypic plasticity is an important mechanism for plant adaptation to variable environments, and plant responses to changing climates. However, plasticity in fitness or performance traits (i.e. fecundity, biomass, growth rate) is generally not adaptive since plasticity in these traits would require low fitness or poor performance in some environments. I assessed the use of plasticity in fitness and performance traits in recent plasticity studies, and in studies where I have recently acted as a reviewer or editor. I found that approximately one third of studies include plasticity in fitness and/or performance traits in their assessment of potentially adaptive responses to environmental variability. Misinterpreting plasticity may be due the simplicity and power of plasticity to investigate adaptation to heterogeneous environments, but no guidelines of how to interpret plasticity in fitness and performance traits. This review highlights the extent of the problem of misinterpreting plasticity, and as a guide to interpreting adaptive and maladaptive plastic responses in plants.