An experimental test of the effects of temperature and resource quality on carrying capacity

The metabolic theory of ecology links the effects of temperature on metabolic rates at the cellular scale to larger-scale ecological processes, providing a framework for predicting how individuals, populations and communities will respond to climate change. Metabolic theory predicts that carrying capacity will have a unimodal (hump-shaped) response to temperature, and that this relationship could be altered by resource availability. However, few studies have empirically tested these predictions, despite the fundamental role that carrying capacity plays in governing population and community dynamics. To test the effect of temperature on carrying capacity and to determine whether this is mediated by resource quality, we conducted a fully crossed experiment in which we grew populations of the model organism Tribolium castaneum for 22 weeks at all 12 treatment combinations of four temperatures (27.5, 30, 32.5, 35°C) and three resource qualities (flour mixtures). Our results support the prediction that carrying capacity has a unimodal relationship with temperature, however resource quality did not alter this relationship. These findings support emerging theory describing temperature's effect on carrying capacity, and contribute to our understanding of how population dynamics will shift under climate change.