General predictions for the effects of warming on competition

Understanding the effects of climate change on communities has been hindered by a lack of general theory for how temperature affects competition. To fill this knowledge gap, we integrated Modern Coexistence Theory and the Metabolic Theory of Ecology by incorporating empirically-derived temperature sensitivities into Modern Coexistence Theorys central model. We then simulated warming in two-consumer, two-resource systems and found that warming reduced both niche and fitness differences, making species more ecologically similar, and competitive interactions more neutral. The greatest shifts in competition occurred when thermal responses among consumers or resources were highly asymmetrical. Effects of warming on competition via niche differences were comparable to or stronger than those on fitness differences, suggesting that the emphasis on vital rates in global change research may overlook key biodiversity drivers. Our general theory expands the domains of two prominent ecological theories and contributes to a more predictive understanding of global change.