McCauley等人将理论与实验结合在一起，来探索产生不同类型捕食者-猎物循环的动态机制。他们的理论预测到一种新型的小幅度循环，该循环与耦合的消费者-资源体系中的大幅度波动共存。他们还发现，具有所预测到的特征的小幅度循环出现在食草水蚤（Daphnia pulex）及它们的藻类猎物的种群中。这些发现也许可解释为什么小幅度循环在捕食者-猎物体系中普遍存在，因而也可解释它们的相对稳定性。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 455, 1240-1243 (30 October 2008) | doi:10.1038/nature07220
Small-amplitude cycles emerge from stage-structured interactions in Daphnia–algal systems
Edward McCauley1, William A. Nelson2 & Roger M. Nisbet3
1 Ecology and Evolution Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada
2 Department of Biology, Queen's University, Kingston, Ontario K7L 3N6, Canada
3 Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California 93106, USA
A long-standing issue in ecology is reconciling the apparent stability of many populations with robust predictions of large-amplitude population cycles from general theory on consumer–resource interactions1. Even when consumers are decoupled from dynamic resources, large-amplitude cycles can theoretically emerge from delayed feedback processes found in many consumers2, 3. Here we show that resource-dependent mortality and a dynamic developmental delay in consumers produces a new type of small-amplitude cycle that coexists with large-amplitude fluctuations in coupled consumer–resource systems. A distinctive characteristic of the small-amplitude cycles is slow juvenile development for consumers, leading to a developmental delay that is longer than the cycle period. By contrast, the period exceeds the delay in large-amplitude cycles. These theoretical predictions may explain previous empirical results on coexisting attractors found in Daphnia–algal systems4, 5. To test this, we used bioassay experiments that measure the growth rates of individuals in populations exhibiting each type of cycle. The results were consistent with predictions. Together, the new theory and experiments establish that two very general features of consumers—a resource-dependent juvenile stage duration and resource-dependent mortality—combine to produce small-amplitude resource–consumer cycles. This phenomenon may contribute to the prevalence of small-amplitude fluctuations in many other consumer–resource populations6, 7.
