【作者】 苏敏；

【导师】 李自珍；

【作者基本信息】 兰州大学 ， 应用数学， 2009， 博士

【副题名】破碎化生境、Allee效应及空间尺度对传播动态的影响

【摘要】 生态传染病学这一新兴的交叉学科已成为当今生物数学研究中的前沿与热点。本论文选题于该领域的新焦点,即具有空间结构的生态传染病。空间生态传染病理论的提出扩展和丰富了种群及群落传染病研究,为环境变化和栖息地破坏下遭受疾病感染的濒危物种的研究提供了新颖的理论依据,并与空间技术相结合为从不同尺度研究疾病传播规律提供了深层次的生态与模型机理。本论文首先对生态传染病学的概念,理论,研究现状与进展进行综述,进而介绍了空间生态传染病的相关理论及模型;其次,基于疾病在捕食者中传播的生态传染病模型研究了Allee效应可能产生的复杂性动态以及疾病传播的时空动态与空间尺度,随机生境破坏和统计随机性之间的关系;再次,揭示生境破坏引起的空间环境异质性是如何影响空间宿主-寄生传染病系统中病毒的入侵,传播及物种分布模式,并阐述空间异质性的两个组分(丧失斑块的数量及其聚集程度)之间的相互关联性;最后,建立了宿主-寄生-捕食生态传染病模型,重点研究了生境破坏的不同空间格局对生态传染病动态的影响,并阐述了生态传染病系统内在的生物机制。其中,对捕食-食饵作用的生态传染病模型进行空间上的延伸以及讨论具有空间结构的生境破坏对生态传染病系统动态的影响都属于创新性的工作。论文主要采用两种研究手法:一是构建微分动力系统模型,例如偶对近似模型,利用相平面分析以及数值解对系统的平衡点及其稳定性进行阐述;二是建立空间显含的模拟模型,实现空间模式、结构与动态的可视化,弥补空间隐含模型对空间结构研究的不足。通过上述几个方面的研究,主要得出如下新结果:(1)Allee效应在种群动态中扮演稳定还是不稳定角色取决于它的强度;(2)感染率和捕食率都是影响生态传染病系统中物种空间模式的关键因素;(3)均匀场假设、局部相互作用以及统计随机性对病毒入侵和分布模式均有着重要的影响;(4)种群个体间相互作用的空间尺度复杂地影响了疾病传播的时空动态。随着邻体数目的增加,病毒的感染力度变得更大而且在空间上形成聚集的波形;(5)生境破坏及其空间结构在一定范围内有利于疾病的控制,这暗示人为对生境的干扰可作为疾病控制的一个潜在方法;(6)生境破坏的数量以及不同类型生境的空间分布格局都显著地影响了寄生病毒的入侵和传播,生境破碎化程度越高(高丧失斑块的数量或低聚集程度),将越有害于病毒的入侵和传播,这暗示了空间异质性是否有益于物种的入侵依赖于所考虑的生态过程;(7)由生境破坏引起的空间异质性的两个组分之间存在负偶联关系(trade-off);(8)在适度的生境破坏范围内,宿主种群能够平衡生境破坏带来的正负两种效应并呈现增长趋势;(9)在捕食-食饵系统中,寄生感染病毒极有可能在生境破坏量较低时爆发;(10)物种在面临生境破坏或者其它环境压力时表现出更高的聚集分布策略;(11)寄生-宿主/食饵-捕食生态传染病系统与共位捕食(intraguild predation)食物网结构具有相似的生物机制,其中捕食者扮演共位捕食者的角色,已感染食饵作为共位食饵,易感染食饵扮作共同消耗的资源;(12)位于最高营养级水平的种群对生境破坏的响应不一定是最敏感的,这不仅依赖于内在的生物机制同时也依赖于外在的环境干扰。更多还原

【Abstract】 Eco-epidemiology is a newly emerged cross discipline and now has been the frontiers and hotspots in the research of mathematical biology. The subject of this dissertation is the spatial eco-epidemiology, which is a new focus of this field. Spatial eco-epidemiology has extended and enriched the research of population and community epidemiology. It provides novel theoretical grounds for endangered species suffering a disease with the environmental changes and habitat destruction. Combined with spatial technology, it has provides deep ecological mechanisms for disease transmission at different scales. We firstly summarize the concept, theory, frontiers and development of eco-epidemiology in detail, and then discuss the theories and models in spatial eco-epidemiology. Secondly, based on the eco-epidemiological model where the predator suffering the epidemic, we investigate the complex dynamics due to Allee effect, and the effects of spatial scale, habitat loss and demographic stochasticity on the spatiotemporal dynamics of the epidemic transmission. Thirdly, we reveal how the spatial landscape heterogeneities due to habitat loss affect the invasion, transmission and distribution patterns in host-parasite epidemic system, and illustrate the relation between the two components of spatial heterogeneities. Finally, we construct the host-parasite-predation eco-epidemiologic model, and study primarily the effects of habitat loss with different spatial configuration on the dynamics of eco-epidemiologic system, and also explore the interal biological mechanism of eco-epidemiology. Among of them, the extension with eco-epidemiological model on predator-prey interactions at spatial scale, and discussion the effects of spatial structure of habitat loss on eco-epidemiological systems both are innovative works. Two approaches will be utilized in this dissertation. One is the differential dynamical system, such as pair approximation. I will use the phase plane analysis and numerical solution to illustrate the equilibriums and their stability of the system. The other is constructing the spatially explicit simulation, and then to achieve the explicit graphic mode of the spatial pattern, structure and dynamics, which can make up for the deficiency of spatially implicit model. We have obtained the following new results: (1) Allee effect is a stabilizing or a destabilizing force in ecological systems could be determined by its intensity. (2) The infection rate and predation rate both are the key factors which affecting the spatial patterns of species in the eco-epidemiological systems. (3) Mean-field assumption, local interaction and demographic stochasticity have great influence on the disease invasion and distribution patterns. (4) Spatial scale of interactions between individuals affects complexly the spatiotemporal dynamics of epidemic transmission. With increasing of neighborhood size, the infected force become stronger and form aggregated spreading wave. (5) At a certain range, habitat loss and its spatial structure can benefit the control of the epidemic disease, which indicates the possibility of using human disturbance in habitat as a potential epidemic-control method in conservation. (6) Not only the quantity of habitat loss but also the spatial correlations of patch types caused by nonrandom habitat loss affect the invasion and transmission of disease. More fragmented landscape (high amount of habitat loss, low clustering of lost patches) hinders the parasitic infection, which also indicates that whether the spatial heterogeneity benefits or hinders the invasion is dependent on the considered ecological process. (7) Two components of the spatial heterogeneity (the amount and spatial autocorrelation of the lost habitat) form a trade-off in determining the host-parasite dynamics. (8) Within a certain range of habitat loss, host can counterbalance the positive and negative effects, and shows a rising tendency. (9) The epidemic is more likely to break out in the prey-predator system if only a small amount of habitat loss. (10) A highly aggregated distribution of species is a common behavioral strategy when dealing with habitat loss or other environmental stresses. (11) The parasite-host/prey-predator eco-epidemiological systems have the similar mechanism with the intraguild predation systems, and the predator acts as the intraguild predation, the infected prey acts as intraguild prey, and the susceptible prey acts as shared resource. (12) Species at the highest trophic level are no longer affected the most by habitat loss, which depend not only on the biological mechanism but also on the external environmental disturbances.更多还原