Abstract
The structure of food webs is frequently described using phenomenological stochastic models. A prominent example, the niche model, was found to produce artificial food webs resembling real food webs according to a range of summary statistics. However, the size structure of food webs generated by the niche model and real food webs has not yet been rigorously compared. To fill this void, I use a body mass based version of the niche model and compare prey-predator body mass allometry and predator-prey body mass ratios predicted by the model to empirical data. The results show that the model predicts weaker size structure than observed in many real food webs. I introduce a modified version of the niche model which allows to control the strength of size-dependence of predator-prey links. In this model, optimal prey body mass depends allometrically on predator body mass and on a second trait, such as foraging mode. These empirically motivated extensions of the model allow to represent size structure of real food webs realistically and can be used to generate artificial food webs varying in several aspects of size structure in a controlled way. Hence, by explicitly including the role of species traits, this model provides new opportunities for simulating the consequences of size structure for food web dynamics and stability.
Highlights
Animal communities form complex networks of interspecific interactions; the most traditionally studied type of such networks is the food web [1]
Food webs generated by the original niche model have median predator-prey body mass ratios (PPMR) = 253.8, while food webs produced by the two traits allometric model with no, weak and strong effect of the foraging trait have median PPMR = 191.4, 122.4 and 79.1, respectively
The distributions of all summary statistics overlapped (99% intervals overlapped in all metrics; in most cases the overlap was much larger), so the difference between model settings was not significant
Summary
Animal communities form complex networks of interspecific interactions; the most traditionally studied type of such networks is the food web [1]. We need to develop models that faithfully represent the empirically observed dependence of predation links on body masses of predators and prey to gain better insights into the structure and stability of food webs. The original niche model and its modifications have been found to describe the structure of real food webs faithfully [17,18,20,23,24]. It is widely recognized that predator and prey masses are strongly correlated in real food webs [8,9,10,11] Testing whether this correlation is reproduced by theoretical food web models is of utmost importance
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