Dynamics of evolutionary patterns of clades in a food web system model

Abstract

The evolutionary patterns of animal species clades in an evolving food web system were examined by computer simulation. In this system, each animal species fed on other species according to feeding preference. The food web system evolved via the appearance and extinction of species. The model succeeded in reproducing evolutionary patterns of diversity similar to those seen in the fossil record. This result indicates that the model reproduced the temporal changes of the rates of colonization and extinction of species in the system, which have been decided a priori in the previous stochastic models. In the food web system, the numbers of both predatory and prey species influenced the temporal diversity patterns in each clade in the system. The number of prey species fluctuated strongly, whereas the number of predatory species gradually increased with time. Therefore, temporal diversity patterns were influenced mainly by the number of predatory species. As a result of the gradual increase of the number of predatory species, it was difficult for each clade to maintain its species diversity for a long time. Slight changes of interspecific interaction can sometimes decide the destiny of a clade. When a clade is faced with extinction, if one predatory species of the clade becomes extinct and one or two prey species of the clade appear, the species diversity in the clade increases again. This result indicates that slight changes of interspecific interaction sometimes decide the destiny of a clade.