UW Aquatic & Fishery Sciences Quantitative Seminar

Carl Walters

Institute for the Oceans and Fisheries & Department of Zoology, University of British Columbia

Predicting covariation in predator and prey abundances across productivity gradients: why Hatton et al 2015 have missed the basic issue

Abstract

A paper by Hatton et al just out in Science suggests that predator and prey average (or equilibrium) abundances covary as a simple power relationship with power around 0.75. They assert that this pattern is not predicted by classic predator-prey theory or by logistic prey population growth models, and that it is caused by non-logistic density dependence in prey dynamics. This is incorrect, since they are comparing equilibrium prey densities across productivity gradients for which the density-dependence parameters of the prey are expected to change. A number of other mechanisms can explain the pattern or "law" that they propose, and a basic understanding of predator-prey isocline theory helps to see these possibilities.