Agglomeration Effects Of Metapopulation Evolution Studies

The species spatial distribution plays an important role in both the intraspecies competition and the interspecies competition. The aggregation effect due to the species spatial distribution is not ignored in the evolution of the metapopulation. How does the evolution of the metapopulation when considering the aggregation effect?On the basis of the previous theories of the metapopulation and the aggregation effect, this paper explored the evolution law of the metapopulation when the habitat changed, through constructing the models and simulations. On the one hand, the ecological concepts, aggregation index, the most comfortable aggregation index and the aggregation effect were proposed. And then the dynamical model of the metapopulation under the aggregation effect was set up combining the Tilman's multi-species competition model. On the basis of the models, the evolution law of the metapopulation was explored when the habitat was destroyed and not destroyed. On the other hand, the real species distribution was obtained by the neutral landscape model. The evolution law of the metapopulation also was investigated by the Cellular Automata model. In the end, the effect to the metapopulation due to the aggregation effect was comprehensively investigated by rationally designing the parameters and a bulk of simulations. The main results were obtained as following:(1) the effect to the intraspecies and the interspecies competition resulted from the aggregation index of the species distribution was included in the dynamical model of the metapopulation under aggregation effect. This model become to the Tilman's model when every species in the system was the most comfortable aggregation index. So this model was more general than the Tilman's. (2)The evolutions of the metapopulation become more complicated because of the aggregation effect. Firstly, there was a quasi-period fluctuation when the metapopulation system reached equilibrium state though the habitat was not destroyed. Secondly, the ecological order showed disorder under the habitat was destroyed when the system reached the equilibrium. (3) The ecological order of persisting species in equilibrium was generally determined by the individuals'competitive strength, breeding rate and mortality rate as well as the interspecific competitive strength. But in this research, it showed that the aggregation effect and the habitat occupied rate of the constructive species in the community were the two key factors that essentially determine the landscape ecological sequence.(4) Another mechanism of the species extinction is discovered. The critical condition of the first species extinction become smaller and the extinct debt become larger due to the aggregation effect. In some communities the endangered species went extinct because the negative aggregation effect due to the uncomfortable aggregation index.(5)The simulations of the spatial explicit model also indicated that the evolution of the metapopulation become more complicated when considering the species distribution. The colonization and diffusion of species was affected by the aggregation effect due to the species distribution. (6)The size of the habitat was not the decisive factor to the evolution of the metapopulation. The structure of the habitat was more important than the size of the habitat. (7)The response of the community in different aggregation index to the habitat destruction was similar. The loss of the diversity would more serious when the habitat was few and more fragmented.