U.S. Geological Survey, Department of Biology, University of Miami, Coral Gables, Florida USA, 33124.
Am Nat. 2011 Jul;178(1):15-29. doi: 10.1086/660280.
A key assumption of the ideal free distribution (IFD) is that there are no costs in moving between habitat patches. However, because many populations exhibit more or less continuous population movement between patches and traveling cost is a frequent factor, it is important to determine the effects of costs on expected population movement patterns and spatial distributions. We consider a food chain (tritrophic or bitrophic) in which one species moves between patches, with energy cost or mortality risk in movement. In the two-patch case, assuming forced movement in one direction, an evolutionarily stable strategy requires bidirectional movement, even if costs during movement are high. In the N-patch case, assuming that at least one patch is linked bidirectionally to all other patches, optimal movement rates can lead to source-sink dynamics where patches with negative growth rates are maintained by other patches with positive growth rates. As well, dispersal between patches is not balanced (even in the two-patch case), leading to a deviation from the IFD. Our results indicate that cost-associated forced movement can have important consequences for spatial metapopulation dynamics. Relevance to marine reserve design and the study of stream communities subject to drift is discussed.
理想自由分布（IFD）的一个关键假设是在栖息地斑块之间移动没有成本。然而，由于许多种群在斑块之间或多或少地持续进行种群移动，并且迁移成本是一个常见的因素，因此确定成本对预期种群移动模式和空间分布的影响非常重要。我们考虑了一个食物链（三营养级或双营养级），其中一个物种在斑块之间移动，在移动过程中有能量成本或死亡率风险。在两斑块情况下，假设单向强制移动，进化稳定策略需要双向移动，即使在移动过程中成本很高。在 N 斑块情况下，假设至少有一个斑块与所有其他斑块双向连接，最优的移动速度可能导致源汇动态，其中具有负增长率的斑块由具有正增长率的其他斑块维持。同样，斑块之间的扩散是不平衡的（即使在两斑块情况下），导致偏离 IFD。我们的结果表明，与成本相关的强制移动可能对空间复合种群动态产生重要影响。讨论了与海洋保护区设计和受漂流影响的溪流群落研究的相关性。
