Temperature Variability Has Limited Effects on Phenotypic Plasticity in Ectotherms—A Meta-Analysis

Phenotypic plasticity can lead to compensation for potentially adverse effects of variation in the thermal environment so it is important to understand the impacts of changes in mean and fluctuations in temperature on plastic responses. Here we establish the current state of knowledge of how thermal variability influences the expression of phenotypic plasticity in ectothermic animals. Our quantitative synthesis of 46 studies compares the effects of constant and fluctuating temperatures with the same mean on plasticity in different traits, across different ecosystems (terrestrial and aquatic) and between types of phenotypic plasticity (acclimation and developmental plasticity). We found that 98% of studies implemented diel temperature fluctuations and most data were derived from invertebrates. We show that plasticity does not differ between constant and fluctuating environments except for weak effects on developmental time. We conclude that plasticity is more likely to be driven by changes in longer-term mean temperatures.