Data from: Predictive power of food web models based on body size decreases with trophic complexity

Food web models parameterized using body size show promise to predict trophic Interaction Strengths (IS) and abundance dynamics. However, this remains to be rigorously tested in food webs beyond simple trophic modules, where indirect and intraguild interactions could be important and driven by traits other than body size. We systematically varied predator body size, guild composition and richness in microcosm insect webs and compared experimental outcomes with predictions of IS from models with allometrically scaled parameters. Body size was a strong predictor of IS in simple modules (r2=0.92), but with increasing complexity the predictive power decreased, with model IS being consistently overestimated. We quantify the strength of observed trophic interaction modifications, partition this into density-mediated vs. behaviour-mediated indirect effects and show that model shortcomings in predicting IS is related to the size of behaviour-mediated effects. Our findings encourage development of dynamical food web models explicitly including and exploring indirect mechanisms.基于体型参数化的食物网模型，在预测营养交互强度（trophic Interaction Strengths，IS）与种群丰度动态方面颇具应用前景。然而，这一结论仍需在简单营养模块之外的食物网中开展严格验证——在这类食物网中，间接互作与集团内互作往往发挥关键作用，且其驱动因子并非仅局限于体型大小。我们在微型昆虫食物网微宇宙中系统调控捕食者体型、功能群组成与物种丰富度，并将实验结果与基于异速标度参数的模型所预测的营养交互强度进行对比。在简单营养模块中，体型可较好预测营养交互强度（r²=0.92）；但随着系统复杂度提升，模型的预测能力逐渐下降，且模型预测的营养交互强度始终偏高。我们量化了观测到的营养互作修饰强度，并将其拆解为密度介导与行为介导的两类间接效应，同时发现模型在预测营养交互强度时的缺陷与行为介导效应的强度存在显著相关性。本研究结果为开发明确纳入并探究间接作用机制的动态食物网模型提供了重要助力。