Trophic cascades have become a dominant paradigm in ecology, yet considerable debate remains about the relative strength of density- (consumptive) and trait-mediated (non-consumptive) effects in trophic cascades. This debate may, in part, be resolved by considering prey experience, which shapes prey traits (through genetic and plastic change) and influences prey survival (and therefore density). Here, we investigate the cascading role of prey experience through the addition of mosquitofish (Gambusia affinis) from predator-experienced or predator-naïve sources to mesocosms containing piscivorous largemouth bass (Micropterus salmoides), zooplankton, and phytoplankton. These two sources were positioned along a competition-defense tradeoff. Results show that predator-naïve mosquitofish suffered higher depredation rates, which drove a density-mediated cascade, whereas predator-experienced mosquitofish exhibited higher survival but fed less, which drove a trait-mediated cascade. Both cascades were similar in strength, leading to indistinguishable top-down effects on lower trophic levels. Therefore, the accumulation of prey experience with predators can cryptically shift cascade mechanisms from density- to trait-mediated.

中文翻译：

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猎物在竞争防御权衡下的适应性将营养级联从密度介导的转化为性状介导。

营养级联已经成为生态学中的主导范式，但是关于营养级联中的密度（消耗性）和性状介导的（非消耗性）效应的相对强度仍然存在很多争论。可以通过考虑猎物的经验来解决这场辩论，猎物的经验会塑造猎物的性状（通过遗传和塑性变化）并影响猎物的生存（从而影响密度）。在这里，我们研究了捕食经验的级联作用，方法是将捕食者经历过或捕食者原始来源的蚊子（Gambusia affinis）添加到含有食性大嘴鲈（Micropterus salmoides），浮游动物和浮游植物的中胚层中。这两个消息来源是在竞争与防御的权衡中定位的。结果表明，天敌幼稚的蚊鱼遭受了更高的捕食率，它驱使密度介导的级联反应，而体验过捕食者的蚊鱼存活率更高，但进食较少，从而驱使特质介导的级联反应。两个级联的强度相似，导致在较低的营养级上没有明显的自上而下的效果。因此，在捕食者身上积累的猎物经验可以使级联机制从密度介导的转变为性状介导。