Predicting trophic relations in ecological networks: a test of the Allometric Diet Breadth Model

Few of food web theory hypotheses/predictions can be readily tested using empirical data. An exception is represented by simple probabilistic models for food web structure, for which the likelihood has been derived. Here I test the performance of a more complex model for food web structure that is grounded in the allometric scal-ing of interactions with body size and the theory of optimal foraging (Allometric Diet Breadth Model- ADBM). This deterministic model has been evaluated measuring the fraction of trophic relations cor-rectly predicted. I contrast this value with that produced by simpler models based on body sizes and find that the data does not favor the more complex model: the information on allometric scaling and opti-mal foraging does not significantly increase the fit to the data. Also, I take a different approach and compute the p-value for the fraction of trophic interactions correctly predicted by ADBM with respect to three probabilistic null models. I find that the ADBM is clearly bet-ter at predicting links than random graphs, but other models can do even better. Although optimal foraging and allometric scaling could improve our understanding of food webs, the models need to be ame-liorated to find support in the data. 1 a