Simulation Research On Biological Invasion: Influence Of Environmental Colored Noise,Allee Effect And Structures Of Interspecies On Invasion Dynamics

With the globalization of economic, trading and tourism, biological invasion is fast becoming one of the world's most costly ecological problems, which not only disrupts agriculture, but also drastically alters ecosystems, and spreads disease. From the last century, invasion by alien species has increasingly been recognized as one of the major worldwide environmental problems. The subject of our dissertation is the es-sential focus in the field of biological invasion:simulation research on the mechanism of biological invasion. Understanding of mechanisms of biological invasion is an issue of significant current interest in conservation biology and ecology. It plays a major role in the management and control of invasive species. In the present dissertation, firstly, the concept, theory, frontiers and development of biological invasion are summarized, and the models of biological invasion and investigated programs are also showed. Secondly, the invasion patterns of predator-prey system is investigated under the disruption of different colors of environmental noise, and a classification of invasion patterns is discussed in detail. Thirdly, the invasion mechanisms of epidemic is studied through the eco-epidemiological invasion model in the case of the Allee effect on different species. Finally, a theoretical investigation is conducted to study the influence of different invasion strategies on success invasion through a probability transition model, and the common existence of intraguild predation will also be explained from the perspective of biological invasion. Two approaches will be used in this dissertation. One is the invasion system of reaction—diffusion type. Mathematical simulations of this system is resolved by phase plane analysis and finite element method. The numerical solutions of the system can be drawn from this approach. The other is the cellular automata model. This approach can absorb the life history characteristics and stochasticity of species. Through extensive numerical simulations, we have obtained the following new conclusions:(1) The noise color does not have a relatively large impact on invasion patterns of the prey when its intensity is small. However, the spread patterns of the predator are different when the system is affected by the noise of different color; (2) A geographical invasion emerges without regional persistence when the intensity of noise is small;(3) As the noise intensity increases, the species spreads via a patchy invasion only when the system is affected by red noise;(4) The predator, which becomes extinct in the system without diffusion, could invade locally when the system is affected by white noise. However, the local invasion is not followed by geographical spread;(5) The Allee effect has an opposite impact on the invasion criteria when that on the different species; (6) As the intensity of the Allee effect increases, the system dynamics is changed from the stable state to the limit cycle and finally becomes the chaotic state when the susceptible prey with the Allee effect, but the system dynamics is changed from limit cycle to a table point when the predator is subject to the Allee effect; (7) The strong intensity of the Allee effect can lead to the catastrophic global extinction of all species in the case of that on the susceptible prey; (8) When the predator with the Allee effect, the increased intensity of which makes spatial species reach a stable state; (9) In the eco-epidemiological invasion model, two kinds of invasion patterns is found, i.e. travelling fronts and travelling rings. Once the epidemic invasion is successful, the increase of invasion speed will change the invasion patterns from the travelling fronts to the travelling rings;(10) The probability of success invasion is higher when an exotic species invades through intraguild predation than competition and simple food chain;(11) The parameter domain of success invasion is larger under intraguild predation than the other two; (12) From the standpoint of biological invasion, intraguild predation or omnivory is commonly found in nature.