Meeting Abstract

7.1  Jan. 4  The evolution and emergence of food-webs in fluctuating environments: diversity begets stability, or vice versa? PAWAR, S.; University of Texas at Austin samraat@mail.utexas.edu

All natural food-webs are assembled and persist in environments that exert perturbations in energy input as well as living conditions. In this study, we focus on the effects of external stochasticity on food-web emergence, evolution, and persistence. To generate predictions about the effects of different kinds of fluctuations on food-web dynamics, we use a network-theoretic approach. The basic theoretical structure is a weighted, directed graph with nodes representing populations and edges the interactions between them. To consider the effects of environmental stochasticity realistically, we use observed patterns in environmental variables (such as climate) to motivate the models. The results provide insights into the effects of environmental uncertainty on dynamical and structural (topological) properties of food-webs, and indicate that extrinsic stochasticity can have counterintuitive effects. We elucidate the concept of the stochastic �fitness� of a food web, and show that selection on certain life-history parameters of component populations can result in the emergence of persistent food-webs that maximize this fitness. The end result is that given sufficient time for network evolution, dynamical properties such as stability and assembly rate, and topological features such as degree distributions and chain lengths can be expected to be consistently associated with the pattern of stochasticity in the external environment. We discuss the implications of these results for food-web theory, and evaluate some of the predictions with data from real-world webs along environmental gradients.