Supply-Demand Models and the Evolution of Body Size

Body size is of fundamental importance to the structure and function of natural systems, yet the factors selecting for certain body sizes are still not well understood. I developed a simple optimization model for adult (or asymptotic) body size where the optimal size is that which balances the bodily demand for resources with the environmental supply of those resources. These resources are typically food but may also be nutrients or oxygen. The model easily integrates with population dynamics models and can account for a wide range of body size patterns in space and time. Recent experimental work provides quantitative support for model predictions on the effects of temperature on body size, links between body size and growth rate, and dynamic changes in predator body size during predator-prey cycles. The simplicity and quantitative nature of the model sets the stage for understanding a wide array of patterns as well as for making quantitative predictions about body size evolution under novel scenarios, including those related to climate and land use change.