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（primary consumers）面临着资源调控的上行控制（bottom-up）与消费者介导的下行控制（top-down）带来的强烈选择压力，但这两类选择力量的相对重要性仍未明确。本研究开展元分析（meta-analysis），旨在比较下行控制与上行控制对消费者适合度的作用强度，同时纳入可调控上述效应的多项调节变量：食性宽度、取食功能群、生境/环境、上行效应类型、下行效应类型，以及消费者适合度效应的测量方式。我们将分析对象聚焦于物种多样性最高的初级消费者类群——植食性昆虫（herbivorous insects），结果总体显示下行控制的作用强度显著高于上行控制。值得注意的是，咀嚼式、刺吸式与造瘿类植食性昆虫受到下行控制的影响均强于上行控制；无论是自然生境还是人工管控（栽培）环境中，下行控制的作用均强于上行控制；同时寄生性天敌（parasitoids）与捕食者（predators）对植食性昆虫的下行调控强度相当。未来研究应拓展目标消费者类群的研究范围，尤其是针对目前研究不足的陆地生态系统、取食功能群、分类类群以及下行控制因子（如病原物），并检验更为复杂的群落间接互作关系。本研究结果揭示了天敌对植食性昆虫的调控作用强度远超预期，因此在开展昆虫-植物互作研究时，采用三营养级（tri-trophic）研究方法实属必要。