Université Montpellier 2, CNRS, Institut des Sciences de l'Evolution, Place Eugène Bataillon, 34095 Montpellier cedex 5, France.
Proc Biol Sci. 2011 Oct 22;278(1721):3042-9. doi: 10.1098/rspb.2011.0112. Epub 2011 Mar 2.
Classical ecological theory has proposed several determinants of food chain length, but the role of metacommunity dynamics has not yet been fully considered. By modelling patchy predator-prey metacommunities with extinction-colonization dynamics, we identify two distinct constraints on food chain length. First, finite colonization rates limit predator occupancy to a subset of prey-occupied sites. Second, intrinsic extinction rates accumulate along trophic chains. We show how both processes concur to decrease maximal and average food chain length in metacommunities. This decrease is mitigated if predators track their prey during colonization (habitat selection) and can be reinforced by top-down control of prey vital rates (especially extinction). Moreover, top-down control of colonization and habitat selection can interact to produce a counterintuitive positive relationship between perturbation rate and food chain length. Our results show how novel limits to food chain length emerge in spatially structured communities. We discuss the connections between these constraints and the ones commonly discussed, and suggest ways to test for metacommunity effects in food webs.
经典生态学理论提出了几种决定食物链长度的因素，但尚未充分考虑复合种群动态的作用。通过对具有灭绝-定殖动态的斑块状捕食者-猎物复合种群进行建模，我们确定了限制食物链长度的两个不同因素。首先，有限的定殖率将捕食者的占有范围限制在猎物占据的部分地点。其次，内在灭绝率沿营养级链累积。我们展示了这两个过程如何共同减少复合种群中最大和平均食物链长度。如果捕食者在定殖过程中（栖息地选择）跟踪其猎物，并且可以通过对猎物关键率的自上而下的控制（特别是灭绝）来加强这种减少，那么这种减少就会得到缓解。此外，自上而下的定殖和栖息地选择的控制可以相互作用，导致扰动率与食物链长度之间出现反直觉的正相关关系。我们的研究结果表明，在空间结构社区中如何出现新的限制食物链长度的因素。我们讨论了这些约束与通常讨论的约束之间的联系，并提出了在食物网中测试复合种群效应的方法。
