More stressful event does not always depress subsequent life performance

Climate change has led to a substantial increase in intensity and duration of heat waves worldwide. Predicting the ecological impacts of hot events should incorporate both immediate and potential carry-over effects in different intensities of heat waves. Previous studies suggested that higher heat dose in early life stage of insect generally decreased immediate survival and depressed adult reproduction through carry-over effects, or unchanged adult performance through recovery effects. However, our previous study showed a different pattern, in which longer heat exposures in larval stage did not always decrease but sometimes increase the subsequent adult maturation success in the diamondback moth. We speculated that it might be another important pattern in the carry-over effects vs. heat dose, and conducted experiments using a global pest, Plutella xylostella. Our present results suggested that heat exposures in early life stage reduced the immediate survival and produced general declines with significant zigzag fluctuating patterns in subsequent body size and reproduction as exposure durations increased. The similar patterns were also validated in other insect taxa and other stresses by reanalyzing the experiment data from literatures. The finding highlights the importance for differentiating the biological effects and consequences of changes in heat dose at fine scales; daily exposure hours of a hot day should be considered to predict population dynamic under climate change.