Daniel Grunbaum, School of Oceanography, University of Washington

Finding the fudge factor: Effective functional response curves for spatially and temporally heterogeneous consumer-resource interactions.

Friday November 9th, 4pm, Phillips 332
(refreshments served in Phillips 330 starting at 3:30)

Abstract: Ordinary differential equation models of consumer-resource dynamics have provided much of our theoretical understanding of ecological systems. These models represent a macroscopic "mean field'' perspective that lumps together individuals differing in size, stage, mobility, physiological condition, genetic identity, micro-environment and many other details. One payoff of this simplification is a high degree of analytical and numerical tractability. Another is a clear experimental path to estimating regulatory mechanisms such as functional response curves. Functional responses are used in ODE models to estimate mean consumption rates as functions of mean resource and consumer densities. However, in most ecological systems resources and consumers are strongly heterogeneous in time and space. In heterogeneous landscapes, consumers' abilities to exploit resources are constrained by their locomotory biomechanics and searching efficiency. A given quantity of resource can be distributed in many ways, some of which result in higher consumption rates than others by specific types of consumers. This implies that functional responses cannot be functions only of mean resource and consumer densities. They may nonetheless be functions of mean densities along with a small number of other parameters. In this talk I will present dimensional analysis that suggests what the other parameters might be, and how they might be used to derive ODE approximations for mobile consumers of heterogeneous resources using effective functional response curves.