16 Pages

Mechanisms and properties of ratio-dependent multitrophic models with particular reference to logistic food webs

WithAlan Berryman, Xin Chen

Ratio-dependent multitrophic models differ from classic Lotka-Volterra models and their allies in being built upon the economic principle of “diminishing returns” rather than the chemical law of “mass action”. One variant of the ratio-dependent school is the generalized logistic food web model. This model meets with all the criteria for a credible predator-prey model and describes a rich array of complex dynamic behavior. It embeds competition and cooperation in the trophic-interaction structure and is consistent in describing species occupying different trophic levels. Although the logistic model makes no explicit reference to functional responses, type II and III functional response emerge implicitly from the structures of trophic interactions. We discuss some of the insights that emerge from this model with respect to the biological control of pest organisms.