De Roos A M, Schellekens T, Van Kooten T, Persson L
Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94084, 1090 GB Amsterdam, The Netherlands.
Proc Natl Acad Sci U S A. 2008 Sep 16;105(37):13930-5. doi: 10.1073/pnas.0803834105. Epub 2008 Sep 8.
Prey in natural communities are usually shared by many predator species. How predators coexist while competing for the same prey is one of the fundamental questions in ecology. Here, we show that competing predator species may not only coexist on a single prey but even help each other to persist if they specialize on different life history stages of the prey. By changing the prey size distribution, a predator species may in fact increase the amount of prey available for its competitor. Surprisingly, a predator may not be able to persist at all unless its competitor is also present. The competitor thus significantly increases the range of conditions for which a particular predator can persist. This "emergent facilitation" is a long-term, population-level effect that results from asymmetric increases in the rate of prey maturation and reproduction when predation relaxes competition among prey. Emergent facilitation explains observations of correlated increases of predators on small and large conspecific prey as well as concordance in their distribution patterns. Our results suggest that emergent facilitation may promote the occurrence of complex, stable, community food webs and that persistence of these communities could critically depend on diversity within predator guilds.
自然群落中的猎物通常为许多捕食者物种所共有。捕食者在争夺相同猎物的情况下如何共存，是生态学的基本问题之一。在此，我们表明，相互竞争的捕食者物种不仅可能在单一猎物上共存，而且如果它们专门针对猎物的不同生活史阶段，甚至可能相互帮助以维持生存。通过改变猎物的大小分布，一个捕食者物种实际上可能会增加其竞争者可获得的猎物数量。令人惊讶的是，一种捕食者可能根本无法生存，除非其竞争者也存在。因此，竞争者显著扩大了特定捕食者能够生存的条件范围。这种“涌现促进作用”是一种长期的、种群水平的效应，它源于捕食减轻猎物间竞争时，猎物成熟和繁殖速率的不对称增加。涌现促进作用解释了在大小同种猎物上捕食者相关增加的观察结果以及它们分布模式的一致性。我们的结果表明，涌现促进作用可能会促进复杂、稳定的群落食物网的出现，并且这些群落的持久性可能严重依赖于捕食者 guilds 内部的多样性。
