Resource-dependent development mediates effects of increased temperature on the dynamics of populations

We study the effects of changes in temperature on the dynamics of a size structured consumer population with resource-dependent growth. A basic feature of increased temperature is that it leads to increased productivity, as more energy is mobilized at the bottom of the food web. Simultaneously, it increases all physiological process rates, increasing both growth and reproductive capacity, but also energetic maintenance cost of individual consumers. Each of these temperature effects can in itself profoundly affect population dynamics: Increased productivity generally increases the likelihood of consumer-resource cycles. Increased growth capacity reduces developmental delays. Increased fecundity may intensify resource competition among young individuals. Finally, increased maintenance cost makes individuals less resistant to periods of low food density. Using a mechanistic individual based approach, we study how the above effects of temperature affect population dynamics. We show how feedbacks through resource-dependent growth can either dampen or amplify the effects of a temperature change, depending on specific temperature scaling of the different aspects under study. This allows us to make predictions about how species with different life history types will respond to increased temperature. For example, when the temperature scaling of fecundity is relatively fast, effects of warming can be dampened by increased starvation mortality of small individuals. When maintenance cost increases relatively fast with temperature, sudden and unexpected population collapse may result from warming.