Development of insects under fluctuating temperature: a review and case study

The relationship between temperature and the developmental rate of organisms is crucial for understanding a variety of biological processes. It is common to use an average-based index of temperature, for example degree-days, for examining the relationship; and relatively little attention has been given to the variance of temperature. In this study, we examined the importance of temperature fluctuation on the development of organisms by compiling published studies. Published studies have shown highly variable results where the developmental rate was sometimes higher and sometimes lower under static temperature compared with variable temperature. A laboratory experiment on Megaselia scalaris showed that M.scalaris developed faster under fluctuating temperature than static temperature. We tested an additive model to predict the effect of fluctuating temperature on development and found that the model was inadequate for making quantitative predictions. However, some qualitative predictions, for example temperature fluctuation has a positive or negative effect, can be successfully predicted by the additive model. Our results show that the effect of temperature on developmental rate is not completely additive and average-based indices such as degree-days cannot be used when quantitative predictions are required.