Data from: Bottom-up vs. top-down effects on terrestrial insect herbivores: a meta-analysis

Primary consumers are under strong selection from resource (“bottom-up”) and consumer (“top-down”) controls, but the relative importance of these selective forces is unknown. We performed a meta-analysis to compare the strength of top-down and bottom-up forces on consumer fitness, considering multiple predictors that can modulate these effects: diet breadth, feeding guild, habitat/environment, type of bottom-up effects, type of top-down effects and how consumer fitness effects are measured. We focused our analyses on the most diverse group of primary consumers, herbivorous insects, and found that in general top-down forces were stronger than bottom-up forces. Notably, chewing, sucking and gall-making herbivores were more affected by top-down than bottom-up forces, top-down forces were stronger than bottom-up in both natural and controlled (cultivated) environments, and parasitoids and predators had equally strong top-down effects on insect herbivores. Future studies should broaden the scope of focal consumers, particularly in understudied terrestrial systems, guilds, taxonomic groups and top-down controls (e.g. pathogens), and test for more complex indirect community interactions. Our results demonstrate the surprising strength of forces exerted by natural enemies on herbivorous insects, and thus the necessity of using of a tri-trophic approach when studying insect-plant interactions.

初级消费者面临着来自资源上行（bottom-up）与消费者下行（top-down）调控的强烈选择压力，但这两种选择力的相对重要性仍未明确。本研究开展了一项元分析（meta-analysis），以比较下行与上行调控力对消费者适合度的影响强度，同时纳入了可调控这些效应的多项预测因子：食性宽度、取食功能群、生境/环境、上行调控效应类型、下行调控效应类型，以及消费者适合度效应的测量方式。我们将分析聚焦于物种多样性最高的初级消费者类群——植食性昆虫，结果发现总体而言下行调控力的强度高于上行调控力。值得注意的是，咀嚼式、刺吸式以及虫瘿形成类的植食性昆虫受下行调控的影响显著强于上行调控；无论是在自然还是受控（栽培）环境中，下行调控力均强于上行调控；而寄生性天敌（parasitoids）与捕食性天敌对昆虫植食者的下行调控效应强度相当。未来的研究应拓展目标消费者类群的研究范围，尤其是在研究程度较低的陆地生态系统、功能群、分类类群以及下行调控因子（如病原物）中，并开展更为复杂的群落间接互作相关测试。本研究结果证实了天敌对昆虫植食者施加的调控力强度远超预期，因此在研究昆虫-植物互作时，采用三营养级（tri-trophic）研究范式具有必要性。