Effect of the intensity of stochastic disturbance on temporal diversity patterns- A simulation study in evolutionary time scale

摘要

In order to clarify the effect of the intensity of stochastic disturbance on temporal diversity patterns, computer simulations for biodiversity change have been performed on the basis of three different models, stochastic model by Raup et al. [Raup, D.M., Gould, S.J., Schopf, T.J.M., Simberloff, D.S., 1973. Stochastic models of phylogeny and the evolution of diversity. J. Geol. 81, 525-542], food web model by Yoshida [Yoshida, K., 2002. Long survival of "living fossils" with low taxonomic diversities in an evolving food web. Paleobiology 28, 464-473; Yoshida, K., 2003. Dynamics of evolutionary patterns of clades in food web system model. Ecol. Res. 18, 625-637], and newly developed food web model with probabilistic disturbances ("disturbance model"). The Yoshida's food web model exhibited a high performance for mimicking the mean of real food webs in several properties and could well reproduce certain kinds of diversity patterns recognized in the fossil record, very large clades, "living fossil" clades, and rapidly diversified clades, which could not be reproduced by the stochastic model. The results of the disturbance models showed that, if a species in the system was suffered from a disturbance which kills the species at the probability of about 50%, temporal diversity patterns generated by food web dynamics were broken. However, the survivorship curve for clade and the ratio of clades with sudden extinction were not affected. In addition, even considerably severe disturbance, which reduces the biomass of species of average biomass to half, did not affect temporal diversity patterns investigated. In the disturbance model, a species which suffered a serious loss of its biomass from a disturbance quickly recovered from the damage, and the effect of disturbance hardly propagated in the system. Consequently, disturbances rarely influence the food web dynamics.