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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.

在由源和汇组成的异质环境中，我们考虑了两个食饵和捕食者系统，一个是捕食者和一个食饵，另一个是捕食者和两个食饵，我们发现在这两个模型中，如果源的生产力不足以拯救汇斑块中的人口缺陷种群，则捕食者物种都容易灭绝。另一方面，如果食物来源太丰富，两个被捕食物种中的一个可能会因为明显的竞争而灭绝，因为捕食者可以依靠替代猎物来维持庞大的种群。增加捕食者移动速率对捕食者和被捕食者的持续性有相反的影响。高迁移率使捕食者种群面临灭绝的危险，减少了在源栖息地繁殖和生产后代的个体。然后，这可能会促进共存的猎物，通过放松捕食压力和明显的竞争之间的两个猎物物种。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。线性模式与源在一端是有利的捕食者，和离心模式，其中源被包围的汇是有利的猎物。在扩散率较低的情况下，与汇的数量相比，空间的吸引力显得尤为重要。因此，生产力在补丁和补丁之间的连接模式影响种群的持久性不同，这取决于物种所属的营养级。