The effects of the trophic level on the stability of food webs

Abstract

The study of food webs has long been a central topic of ecological research, but the structural effects of trophic level on their stability are still not clear. The work described here addresses the influence of a restriction arising from the trophic level on the network topology of food webs which affects their global behavior. We propose a network model of food webs in which the degree of the effects of the trophic level on speciation can be adjusted continuously by a single parameter. The restriction limits the number of species at each level and the establishment of prey-predator relationships between distant levels. Experimental results show that the restriction contributes to the stability of the ecosystem. This is because the strong restriction keeps less robust species at the lower levels abundant by making the distribution of the number of species at each level flat, while the distribution became an inverse pyramidal structure without the restriction. On the other hand, we found that several features of the network, such as the power-law distribution of coextinction sizes and the number of predators, do not depend on the degree of restriction. We also show several comparisons of the experimental data with empirical data in the fossil records.