The robustness of the Webworld model to changes in its structure

We investigate the robustness of a co-evolutionary model of multi-species communities to changes in its structure. The model has both a conventional population dynamics and a network dynamics through which new species are introduced and unsuccessful species removed. The effect of choosing different forms of population dynamics has already been investigated for this model. Here we study the effects of changing the nature of species interactions and thresholds such as the number of individuals of a species required to be present before that species is said to be extinct. We find that the model is remarkably robust to these changes, with only a very few of the modifications leading to food webs which differ appreciably from those found in the original model. This indicates that many aspects of the structure of the model are not, in general, a factor in determining the nature of the food webs constructed.