Data from: Plant defences limit herbivore population growth by changing predator–prey interactions

Plant quality and predators are important factors affecting herbivore population growth, but how they interact to regulate herbivore populations is not well understood. We manipulated jasmonate-induced plant resistance, exposure to the natural predator community and herbivore density to test how these factors jointly and independently affect herbivore population growth. On low-resistance plants, the predator community was diverse and abundant, promoting high predator consumption rates. On high-resistance plants, the predator community was less diverse and abundant, resulting in low predator consumption rate. Plant resistance only directly regulated aphid population growth on predator-excluded plants. When predators were present, plant resistance indirectly regulated herbivore population growth by changing the impact of predators on the herbivorous prey. A possible mechanism for the interaction between plant resistance and predation is that methyl salicylate, a herbivore-induced plant volatile attractive to predators, was more strongly induced in low-resistance plants. Increased plant resistance reduced predator attractant lures, preventing predators from locating their prey. Low-resistance plants may regulate herbivore populations via predators by providing reliable information on prey availability and increasing the effectiveness of predators.植物品质与天敌是影响植食性昆虫种群增长的关键因子，然而二者如何协同调控植食性种群的机制尚未得到充分阐明。本研究通过调控茉莉酸诱导的植物抗性（jasmonate-induced plant resistance）、天敌群落暴露处理以及植食性昆虫密度，探究这些因子对植食性昆虫种群增长的独立与联合效应。在低抗性植株上，天敌群落多样性与丰度均较高，天敌捕食效率亦随之提升；而在高抗性植株上，天敌群落多样性与丰度均较低，天敌捕食效率随之下降。植物抗性仅在排除天敌的植株上，直接调控蚜虫种群增长；当天敌存在时，植物抗性则通过改变天敌对植食性猎物的作用强度，间接调控植食性昆虫种群增长。植物抗性与捕食作用之间的协同调控机制可能为：水杨酸甲酯（methyl salicylate）——一种可吸引天敌的植食性昆虫诱导的植物挥发物（herbivore-induced plant volatile）——在低抗性植株中被更强程度地诱导表达。植物抗性提升会削弱天敌引诱剂的释放，阻碍天敌定位其猎物。低抗性植株可通过为天敌提供可靠的猎物可利用性信息，并提升天敌捕食效能，借助天敌群落调控植食性昆虫种群。