How does spatio-temporal disturbance influence species diversity in a hierarchical competitive system? Prospective order of species coexistence and extinction
2003
Ohsawa, Kyoko | Kawasaki, Kohkichi | Takasu, Fugo | Shigesada, Nanako
To address how habitat destruction and hierarchical competition among species affect the spatio-temporal dynamics of a multi-species community, we present a compartment model in which multiple species undergo dispersal and competitive interactions in a patchy habitat arranged in a two-dimensional lattice. We assume that disturbances are periodically imposed on some parts of the lattice in a block, followed by a period free of disturbance. For convenience, species are ranked in order of competitive ability. We further assume that the intrinsic growth rate of species i, ε ᵢ , and the dispersal ability, D ᵢ , increase in decreasing order of rank. Our model can analytically determine the exact number of surviving species when disturbance is absent. In the presence of disturbance, we numerically examine how spatio-temporal changes in environmental heterogeneity affect species coexistence and extinction, for the case in which the value of ε ᵢ /D ᵢ monotonically increases or decreases with rank. The results demonstrate that (1) when the interspecific competition is smaller than the intraspecific competition, we can provide predictions on the prospective order of species to be driven extinct and the order of potential species to revive with increasing extents of disturbance; (2) when the interspecific competition is stronger than intraspecific competition, a small difference in the disturbance level can lead to drastic changes in the species composition, their densities and the order of species extinction. In addition, comparison with other similar models reveals that differences in species interaction in local population dynamics critically affect the disturbance-mediated species diversity.
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