Williams Richard J, Berlow Eric L, Dunne Jennifer A, Barabási Albert-László, Martinez Neo D
Romberg Tiburon Center and Department of Biology, San Francisco State University, 3150 Paradise Drive, Tiburon, CA 94920, USA.
Proc Natl Acad Sci U S A. 2002 Oct 1;99(20):12913-6. doi: 10.1073/pnas.192448799. Epub 2002 Sep 16.
Feeding relationships can cause invasions, extirpations, and population fluctuations of a species to dramatically affect other species within a variety of natural habitats. Empirical evidence suggests that such strong effects rarely propagate through food webs more than three links away from the initial perturbation. However, the size of these spheres of potential influence within complex communities is generally unknown. Here, we show for that species within large communities from a variety of aquatic and terrestrial ecosystems are on average two links apart, with >95% of species typically within three links of each other. Species are drawn even closer as network complexity and, more unexpectedly, species richness increase. Our findings are based on seven of the largest and most complex food webs available as well as a food-web model that extends the generality of the empirical results. These results indicate that the dynamics of species within ecosystems may be more highly interconnected and that biodiversity loss and species invasions may affect more species than previously thought.
捕食关系会引发物种的入侵、灭绝以及种群波动，从而极大地影响各种自然栖息地中的其他物种。实证证据表明，这种强烈影响很少会通过食物网传播到距离初始扰动超过三个环节的地方。然而，复杂群落中这些潜在影响范围的大小通常是未知的。在此，我们表明，来自各种水生和陆地生态系统的大型群落中的物种平均相隔两个环节，超过95%的物种通常彼此相隔不超过三个环节。随着网络复杂性增加，更出乎意料的是，随着物种丰富度增加，物种之间的联系更为紧密。我们的研究结果基于七个可用的最大且最复杂的食物网以及一个扩展了实证结果普遍性的食物网模型。这些结果表明，生态系统内物种的动态可能具有更高的相互关联性，生物多样性丧失和物种入侵可能影响的物种比之前认为的更多。
