Temperature-dependent herbivore nutritional traits affect population dynamics and persistence

The nutritional traits of herbivores affect demographic rates and regulate nutrient and energy fluxes among trophic levels. Herbivore nutritional requirements, and the nutrient contents of herbivore biomass, depend on temperature – at temperature extremes, more nutritious food is required to maximize growth rate and herbivore biomass contains fewer nutrients. Yet, the consequences of these thermal responses for the population dynamics of herbivore-autotroph systems have not been explored. Here, we develop and analyze a stoichiometrically-explicit, temperature-dependent model of herbivore-autotroph systems to answer the question: How does the thermal response of herbivore nutritional traits affect population responses to temperature and nutrient (phosphorus) supply? We find that temperature-dependent herbivore nutritional traits restrict the range of temperatures at which herbivore populations persist, reduce the stability of population dynamics at high phosphorus supplies, and limit the herbivore’s capacity to control autotroph population density. These results reflect temperature-dependent changes in the herbivore’s sensitivity to nutrient-poor autotroph biomass and ability to retain nutrients in biomass (and thereby dilute autotroph nutrient contents). The thermal response of herbivore nutritional traits may therefore be an important factor influencing population and community responses to warming and nutrient enrichment.