被蜘蛛捕食的风险改变了食物网的结构，减少了野外当地的食草性

Predators can indirectly enhance plant performance via herbivore suppression, with both prey consumption and changes in prey traits (e.g. changes in foraging behaviour) contributing to the reduction in herbivory. We performed a field experiment to determine the extent of such non-consumptive effects which consisted of repeatedly placing spiders (Pisaura mirabilis) on enclosed plants (Urtica dioica) for cue deposition. Control plants were enclosed in the same way but without spiders. After cue deposition, the enclosures were removed to allow arthropods to colonize the plants and feed on them. Arthropods were removed from the plants before the subsequent spider deposition or control enclosure. During six cycles of enclosure, we quantified leaf damage on the plants. After a seventh cycle, the colonizing arthropods were sampled to determine community composition in relation to the presence/absence of spider cues. We found that the presence of chemotactile spider cues reduced leaf damage by 50 %. In addition, spider cues led to changes in the arthropod community: smaller spiders avoided plants with spider cues. In contrast, the aphid-tending ant Myrmica rubra showed higher recruitment of workers on cue-bearing plants, possibly to protect aphids. Our results show that the risk of spider predation can reduce herbivory on wild plants and also demonstrate that non-consumptive effects can be particularly strong within the predator guild.

捕食者可以通过抑制食草动物间接提高植物性能，捕食食草动物和食草动物特征的变化(例如食草动物觅食行为的变化)都有助于减少食草性。我们进行了一项田间实验，以确定这种非消耗效应的程度（指的应该是食草动物特征的变化），包括重复将蜘蛛(Pisaura Mirabilis)放置在封闭的植物(Urtica Dioica)上进行蜘蛛信息素沉积。对照植物也以同样的方式封闭，但没有蜘蛛。在信息素沉积后，围栏被移除，以便节肢动物能够在植物上定居并以其为食。在随后的蜘蛛信息素沉积或对照围栏之前，将节肢动物从植物中移除。在六个围栏周期中，我们量化了植物叶片的损伤。在第七个周期之后，对定居的节肢动物进行采样，以确定与蜘蛛线索的存在/不存在有关的节肢动物群落组成。我们发现，化学活性蜘蛛线索的存在减少了50%的叶片伤害。此外，蜘蛛线索导致了节肢动物群落的变化：较小的蜘蛛会避开有蜘蛛线索的植物（小蜘蛛怕被大蜘蛛干掉？）。与之形成鲜明对比的是，养蚜小红蚁(Myrmica Rubra)在包含蜘蛛信息素的植物上招收的工蚁数量更多，这可能是为了保护蚜虫。我们的结果表明，被蜘蛛捕食的风险可以减少食草动物对野生植物的食草性，也证明了非消耗性效应在捕食者群体中可能特别强。

原文

Bucher, R., et al. (2015). "Risk of spider predation alters food web structure and reduces local herbivory in the field." Oecologia 178(2): 571-577.