School of Biological Sciences, Washington State University, Vancouver, WA, USA.
Department of Entomology and Nematology, University of California, Davis, CA, USA.
Ecol Lett. 2019 Nov;22(11):1850-1859. doi: 10.1111/ele.13377. Epub 2019 Aug 14.
Most prominent theories of food web dynamics imply the simultaneous action of bottom-up and top-down forces. However, transient bottom-up effects resulting from resource pulses can lead to sequential shifts in the strength of top-down predator effects. We used a large-scale field experiment (32 small islands sampled over 5 years) to probe how the frequency and magnitude of pulsed seaweed inputs drives temporal variation in the top-down effects of lizard predators. Short-term weakening of lizard effects on spiders and plants (the latter via a trophic cascade) were associated with lizard diet shifts, and were more pronounced with larger seaweed inputs. Long-term strengthening of lizard effects was associated with lizard numerical responses and plant fertilisation. Increased pulse frequency reinforced the strengthening of lizard effects on spiders and plants. These results underscore the temporally variable nature of top-down effects and highlight the role of resource pulses in driving this variation.
大多数关于食物网动态的主流理论都暗示着底层和顶层力量的同时作用。然而，资源脉冲产生的短暂底层效应可能会导致顶层捕食者效应的强度依次发生变化。我们使用了一项大规模的野外实验（5 年内对 32 个小岛进行采样）来探究脉冲海藻输入的频率和幅度如何驱动蜥蜴捕食者的顶层效应的时间变化。短期削弱蜥蜴对蜘蛛和植物的影响（后者通过营养级联）与蜥蜴的饮食变化有关，并且在较大的海藻输入时更为明显。长期增强蜥蜴对植物的影响与蜥蜴的数量响应和植物的施肥有关。增加脉冲频率增强了蜥蜴对蜘蛛和植物的强化效应。这些结果强调了顶层效应的时间可变性，并突出了资源脉冲在驱动这种变化中的作用。
