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Effects of Environmental Fluctuations and Habitat Fragmentation on Community Structures

环境波动和栖息地破碎化对群落结构的影响

基本信息

批准号：
07640847
负责人：
NAMBA Toshiyuki
金额：
$ 1.28万
依托单位：
Osaka Women's University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

We have considered two systems of prey and predator, one with a predator and a single prey, and the other with a predator and two prey species, in a heterogeneous environment composed of a source and sinks.We have found that both in these two models, the predator species is vulnerable to extinction, if productivity in the source is insufficient to rescue demographically deficient populations in sink patches. On the other hand, if the source is too rich, one of the two prey species may be driven into extinction by apparent competition, because the predator can maintain a large population by virtue of an alternative prey. Increasing the rate of predator movement has the opposite effects on persistence of prey and predator. High emigration rate exposes the predator population to danger of extinction, reducing individuals that breed and produce offsprings in the source habitat. Then, this may promote coexistence of prey by relaxing predation pressure and apparent competition between two prey species. Spatial arrangement of patches, or connectivity between patches, also influences persistence of species. A linear pattern with the source at one end is profitable for predator, and a centrifugal pattern in which the source is surrounded by sinks is advantageous to prey. It is also reveald that the spatial atrusture is particularly important compared with the number of sinks, when the dispersal rate is low. Therefore, productivity in patches and patterns of connectivity between patches influence persistence of populations differently depending on the trophic level to which the species belong.

我们考虑了两个捕食者和捕食者系统，一个具有一个捕食者和一个被捕食者，另一个具有捕食者和两个被捕食者，在一个源和一个汇组成的异质环境中，我们发现在这两个模型中，如果源的生产力不足以拯救在汇斑块中人口统计上缺乏的种群，捕食者很容易灭绝。另一方面，如果来源太丰富，两个猎物物种中的一个可能会因为明显的竞争而灭绝，因为捕食者可以凭借另一个猎物维持大量种群。捕食者移动速度的增加对捕食者和被捕食者的持久性有相反的影响。高迁移率使捕食者种群面临灭绝的危险，减少了在源头栖息地繁殖和繁殖后代的个体。然后，这可能会通过放松捕食压力和两个猎物物种之间的明显竞争来促进猎物的共存。斑块的空间排列或斑块之间的连通性也影响物种的持久性。源在一端的线性格局对捕食者有利，而源被汇包围的离心型有利于捕食。研究还表明，在扩散速率较低的情况下，与汇的数量相比，空间隆起尤为重要。因此，斑块的生产力和斑块之间的连通性模式根据物种所属的营养水平以不同的方式影响种群的持久性。