ORIGINAL ARTICLE Beyond average: an experimental test of temperature variability on the population dynamics of Tribolium confusum

Abstract The relationship between ectotherm ecology and climatic conditions has been mainly evaluated in terms of average conditions. Average temperature is the more common climatic variable used in physiological and pop-ulation studies, and its effect on individual and population-level processes is well understood. However, the intrinsic variability of thermal conditions calls attention to the potential effects that this variability could have in eco-logical systems. Regarding this point, two hypotheses are proposed. From the allocation principle, it may be inferred that if temperature variability is high enough to induce stress in the organisms, then this extra-cost should reduce the energetic budget for reproduction, which will be reflected in population parameters. Moreover, a mathe-matical property of non-linear functions, Jensen’s inequality, indicates that, in concave functions, like the temperature–reproduction performance function, variabil-ity reduces the expected value of the output variable, and again modifies population parameters. To test these hypotheses, experimental cultures of Tribolium confusum under two different thermal variability regimens were carried out. With these data, we fitted a simple population dynamics model to evaluate the predictions of our hypothesis. The results show that thermal variability reduces the maximum reproductive rate of the population but no other parameters such as carrying capacity or the nonlinear factor in a nonlinear version of the Ricker model, which confirms our hypotheses. This result has important consequences, such as the paradoxical increase in population variability under a decrease in thermal vari-ability and the necessary incorporation of climatic vari-ability to evaluate the net effect of climate change on the dynamics of natural populations