Modeling the effect of temperature on species coexistence

Empirical evidence shows that the energy expenditure—and thus the persistence—of organisms follows a unimodal relationship with temperature and a monotonic relationship with body size. However, most studies integrating these organismal properties into species competition have emphasized only the increasing phase of the thermal response. Understanding how performance declines beyond thermal optima is equally critical if we are to anticipate the impacts of global warming on community composition. Here, we provide a modeling framework to explore the conditions under which temperatures exceeding thermal optima hinder species coexistence. We contrast our theoretical predictions with publicly available experimental data on Drosophila . Our results show that warmer conditions reduce coexistence when species’ preferred temperature ranges scale positively with body size and their maximum metabolic rates occur at optimal temperatures. When species share similar body size and thermal optima, coexistence probability peaks at the optimum but declines more sharply under warming than under cooling. Conversely, when species differ in thermal optima but have similar body size, coexistence probability is highest at temperatures closer to the lower optimum. Together, our work establishes a formal approach to understanding species losses and community reassembly under global warming.