Qualitative predictions in model ecosystems

We compare qualitative predictions of press perturbation response from community matrix models with those of a range of numerical simulations on the same models. A technique of weighting the proportion of countervailing feedback cycles in qualitative response predictions (weighted predictions) was tested against quantitative predictions from the inverse community matrix. Specifically, in nine each of 5- and 10- variable models (of varying complexity) we randomly assigned quantitative values of interaction strength and measured correspondence with qualitative predictions in terms of response strength and sign. Based on the techniques and analyses presented herein, we report an expanded scope of inference for qualitative models of any size and complexity and conclude that system structure is of overriding importance. (C) 2002 Elsevier Science B.V. All rights reserved.