Abstract

Patterns of animal migration and the ecological forces that shape them have been studied for centuries. Yet ecological impacts caused by the migration, such as altered predator–prey interactions and effects on community structure, remain poorly understood. This is to a large extent due to the scarcity of naturally replicated migration systems with negative controls, that is, ecosystems without migration. In this study, we tested whether partial migration of certain species within the overall prey community affects foraging ecology of top predators and thereby alters energy pathways in food webs. We carried out the study in independent replicated freshwater lake systems, four with and four without opportunity for prey migration. Specifically, we compared predator foraging mode in lakes where cyprinid prey fish perform seasonal partial migrations into connected streams with lakes lacking migratory opportunities for prey fish. We found clear seasonal bottom-up effects of prey migration on predators, including changes in size structure and total biomass of ingested prey, size-specific changes in littoral versus pelagic origin of diet, and a higher degree of feast-and-famine for predators in systems with migratory prey. Our analyses further showed that partially migratory prey species constitute a larger part of the prey community in systems that allow migration. Hence, prey migrations have important implications for predator foraging ecology and may cause seasonal shifts in the importance of their supporting energy pathways. We suggest that such bottom-up effects of partial migration may be a widespread phenomenon both in aquatic and in terrestrial ecosystems.

中文翻译：

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动物迁徙的生态后果：猎物的部分迁徙影响捕食者的生态和猎物群落

摘要

几个世纪以来，人们一直在研究动物迁徙的模式及其形成的生态力量。然而，由迁徙引起的生态影响，例如捕食者与猎物之间相互作用的改变以及对社区结构的影响，仍然知之甚少。这在很大程度上是由于缺乏带有负面控制的自然复制的迁移系统（即没有迁移的生态系统）的匮乏。在这项研究中，我们测试了某些物种在整个猎物群落中的部分迁移是否会影响顶级捕食者的觅食生态，从而改变食物网中的能量途径。我们在独立的复制淡水湖泊系统中进行了研究，其中四个有捕食者迁移的机会，有四个没有捕食者迁移的机会。特别，我们比较了塞浦路斯捕食鱼执行季节性部分迁移到相连溪流的湖泊中捕食者的觅食模式，而湖泊缺乏捕捞鱼的迁徙机会。我们发现了捕食者迁移对捕食者的明显的季节性自下而上的影响，包括捕食猎物的大小结构和总生物量的变化，沿海饮食和远洋饮食来源的大小特定变化以及捕食者的盛宴和饥荒程度较高在带有迁徙猎物的系统中。我们的分析进一步表明，在允许迁移的系统中，部分迁徙的猎物物种构成了猎物社区的较大部分。因此，猎物的迁徙对捕食者的觅食生态具有重要意义，并可能导致其支持性能源途径的重要性发生季节性变化。