The temperature dependence of consumer-resource interactions

Background/Question/Methods

Understanding how energy moves between organisms, from resources to consumers, and how these local-scale interactions unite to drive and stabilize patterns at higher levels of ecological organization is a central goal of basic and applied ecology. Our work focuses on consumer-resource (CR) pairs, such as predator-prey, parasitoid-host, herbivore-plant, and can also be applied to autotrophic organisms that ‘consume’ abiotic resources. Our general approach is to dissect CR interactions into their component parts (e.g., encounter rate, detection distance, attack rate, handling time) and to use extensive empirical data and novel theory to explicitly establish the temperature and size dependence at each stage. Environmental temperature strongly influences CR interactions, but neither the empirical or theoretical dimensions of its influence are well understood. CR interactions drive the flux of nutrients and materials in all ecosystems and are therefore a critical element of ecological systems from local to community scales. We derive novel theory and present extensive empirical data to explicitly determine the effects of temperature on CR interactions. Our model makes predictions about the temperature and body size dependence of functional traits central to CR interactions spanning levels of organisation from individuals to populations and communities. We use these predictions to construct CR equations that naturally and explicitly include the scaling of body size and temperature to predict quantities such as equilibrium population size, probabilities of invasions, and coexistence conditions. At each stage we test our model assumptions and predictions with an empirical dataset that represents an unprecedented diversity of CR functional types, species, and habitats. 

Results/Conclusions  

The data we use to test the assumptions and predictions of our theory represents the largest and most comprehensive database of its type ever constructed. To date, research on CR interactions has focused more on the influence of body size than temperature. Our analysis explicitly includes body size, but we particularly focus our discussion on the role of temperature. Our analysis of the empirical data matches our model predictions, including Boltzmann-Arrhenius temperature dependence for velocity and handling time and only slight dependence for detection distance and conversion efficiency. Encounter and consumption rates follow a more complicated temperature dependence and lead to equilibrium abundances that either are constant or that scale with environmental temperature, depending on the temperature dependence for carrying capacity, which is not well established.