The temperature-size rule in the context of Dynamic Energy Budget theory

Abstract

The temperature-size rule (TSR) refers to the observation that a wide variety of organisms reach smaller sizes under warmer temperatures. Although various hypotheses have been stated about the mechanisms underlying TSR, a general understanding is still lacking. In this context, it seems that Dynamic Energy Budget (DEB) theory could be useful, as it constitutes a mechanistic framework that predicts growth and development from individual energetics. However, a critical assumption of this framework is that temperature affects all physiological rates equally, which prevents it from capturing the TSR. It remains an open question if and how the DEB framework can be used to capture the TSR patterns.The model does, however, include a parameter, the food searching rate, that does not need to obey this constraint, as it is a physical rather than a physiological parameter. Here, we aimed to test whether introducing a differing temperature-dependence of food searching rate in DEB models makes it possible to capture the TSR. We parameterized the model using an extensive dataset of Daphnia life history response to temperature. The resulting model was able to capture the decrease of both size at maturity and asymptotic size observed in this dataset.Therefore, DEB models can capture the TSR without any major modification, but only requires to introduce a different function for the temperature dependence of the food searching rate. The mechanism underlying this effect essentially results from increased food limitation at high temperature, which, in combination with the particular allocation scheme of the DEB model, affects differentially growth and development.