Data from: Contrasting effects of aquatic subsidies on a terrestrial trophic cascade

Subsidies from adjacent ecosystems can alter recipient food webs and ecosystem functions, such as herbivory. Emerging aquatic insects from streams can be an important prey in the riparian zone. Such aquatic subsidies can enhance predator abundances or cause predators to switch prey, depending on the herbivores. This can lead to an increase or decrease of in situ herbivores and herbivory. We examined the effects of aquatic subsidies on a simplified terrestrial food web consisting of two types of herbivores, plants and predators (spiders). In our six-week experiment, we focused on the prey choice of the spiders by excluding predator immigration and reproduction. In accordance with predator switching, survival of leafhoppers increased in the presence of aquatic subsidies. By contrast, the presence of aquatic subsidies indirectly reduced weevils and herbivory. Our study shows that effects of aquatic subsidies on terrestrial predators can propagate through the food web in contrasting ways. Thereby, the outcome of the trophic cascade is determined by the prey choice of predators.来自相邻生态系统的生态补给（subsidies）可改变受纳食物网与生态系统功能，例如植食作用。从溪流中羽化的水生昆虫，可成为河岸带的重要猎物资源。此类水生补给可提升捕食者种群丰度，或促使捕食者发生猎物转换，其效应取决于植食性动物的类群。这将导致原位植食性动物种群与植食作用强度出现上升或下降的变化。本研究针对由两类植食性动物、植物以及捕食者（蜘蛛）构成的简化陆地食物网，探究了水生补给的影响效应。在为期六周的控制实验中，我们通过排除捕食者的迁入与繁殖行为，聚焦于蜘蛛的猎物选择策略。与捕食者猎物转换效应相符的是，在水生补给存在的条件下，叶蝉的存活率显著提升。与之形成鲜明对比的是，水生补给的存在间接降低了象鼻虫的种群数量与植食作用强度。本研究证实，水生补给对陆地捕食者的影响可通过食物网以截然相反的路径传递。由此可见，营养级联效应的最终结果由捕食者的猎物选择行为所决定。