Benincà Elisa, Huisman Jef, Heerkloss Reinhard, Jöhnk Klaus D, Branco Pedro, Van Nes Egbert H, Scheffer Marten, Ellner Stephen P
Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Nieuwe Achtergracht 127, 1018 WS Amsterdam, The Netherlands.
Nature. 2008 Feb 14;451(7180):822-5. doi: 10.1038/nature06512.
Mathematical models predict that species interactions such as competition and predation can generate chaos. However, experimental demonstrations of chaos in ecology are scarce, and have been limited to simple laboratory systems with a short duration and artificial species combinations. Here, we present the first experimental demonstration of chaos in a long-term experiment with a complex food web. Our food web was isolated from the Baltic Sea, and consisted of bacteria, several phytoplankton species, herbivorous and predatory zooplankton species, and detritivores. The food web was cultured in a laboratory mesocosm, and sampled twice a week for more than 2,300 days. Despite constant external conditions, the species abundances showed striking fluctuations over several orders of magnitude. These fluctuations displayed a variety of different periodicities, which could be attributed to different species interactions in the food web. The population dynamics were characterized by positive Lyapunov exponents of similar magnitude for each species. Predictability was limited to a time horizon of 15-30 days, only slightly longer than the local weather forecast. Hence, our results demonstrate that species interactions in food webs can generate chaos. This implies that stability is not required for the persistence of complex food webs, and that the long-term prediction of species abundances can be fundamentally impossible.
数学模型预测，竞争和捕食等物种间相互作用可能会产生混沌现象。然而，生态学中混沌现象的实验证明却很稀少，并且仅限于持续时间较短且物种组合人为设定的简单实验室系统。在此，我们展示了在一个关于复杂食物网的长期实验中首次出现的混沌现象的实验证明。我们的食物网取自波罗的海，由细菌、几种浮游植物物种、食草和食肉浮游动物物种以及腐食动物组成。该食物网在实验室中型生态系统中培养，每周采样两次，持续超过2300天。尽管外部条件恒定，但物种丰度在几个数量级上呈现出显著波动。这些波动表现出各种不同的周期性，这可归因于食物网中不同的物种间相互作用。每个物种的种群动态都具有相似大小的正李雅普诺夫指数。可预测性仅限于15 - 30天的时间范围，仅比当地天气预报略长一点。因此，我们的结果表明食物网中的物种间相互作用能够产生混沌现象。这意味着复杂食物网的持续存在并不需要稳定性，而且从根本上来说，对物种丰度进行长期预测可能是不可能的。
