The Influence of Predator-Prey Population Dynamics on 
    the Long Term Evolution of Food Web Structure
Barbara Drossel, Paul G Higgs and Alan J McKane
University of Manchester, UK.

We develop a set of equations to describe the population dynamics of many interacting species in food webs. Predator-prey interactions are non-linear, and are based on ratio-dependent functional responses. The equations account for competition for resources between members of the same species, and between different species. Predators divide 
their total hunting/foraging effort betwen available prey species according to an evolutionarily stable strategy (ESS). The ESS foraging behaviour does not correspond to  the predictions of optimal foraging theory. 
     We use the population dynamics equations in simulations of the Webworld model of evolving ecosystems. New species are added to an existing food web by speciation events, whilst species become extinct due to coevolution and competition. We study the dynamics of species diversity in Webworld on a macroevolutionary timescale. A continuous overturn of species is observed, and significant fluctuations occur in the diversity. However, very large scale extinction avalanches appear to be absent from the dynamics and we 
find no evidence for self-organised criticality.

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