From theory to experimental design—Quantifying a trait-based theory of predator-prey dynamics

Successfully applying theoretical models to natural communities and predicting ecosystem behavior under changing conditions is the backbone of predictive ecology. However, the experiments required to test these models are dictated by practical constraints, and models are often opportunistically validated against data for which they were never intended. Alternatively, we can inform and improve experimental design by an in-depth pre-experimental analysis of the model, generating experiments better targeted at testing the validity of a theory. Here, we describe this process for a specific experiment. Starting from food web ecological theory, we formulate a model and design an experiment to optimally test the validity of the theory, supplementing traditional design considerations with model analysis. The experiment itself will be run and described in a separate paper. The theory we test is that trophic population dynamics are dictated by species traits, and we study this in a community of terrestrial arthropods. We depart from the Allometric Trophic Network (ATN) model and hypothesize that including habitat use, in addition to body mass, is necessary to better model trophic interactions. We therefore formulate new terms which account for micro-habitat use as well as intra- and interspecific interference in the ATN model. We design an experiment and an effective sampling regime to test this model and the underlying assumptions about the traits dominating trophic interactions. We arrive at a detailed sampling protocol to maximize information content in the empirical data obtained from the experiment and, relying on theoretical analysis of the proposed model, explore potential shortcomings of our design. Consequently, since this is a “pre-experimental” exercise aimed at improving the links between hypothesis formulation, model construction, experimental design and data collection, we hasten to publish our findings before analyzing data from the actual experiment, thus setting the stage for strong inference.将理论模型成功应用于自然群落，并预测环境变化下的生态系统动态，是预测生态学的核心支柱。然而，检验此类模型所需的实验往往受限于实际操作约束，且模型常被利用并非为其设计的数据集进行机会性验证。与之相对，我们可通过对模型开展深入的实验前分析，来指导并优化实验设计，从而得到更精准针对理论有效性检验的实验方案。本文针对一项特定实验阐述该流程：我们从食物网生态学理论出发，构建模型并设计实验以最优方式检验该理论的有效性，同时结合模型分析补充传统实验设计的考量维度。本实验的具体实施过程与细节将在另一篇论文中予以阐述。我们所检验的理论为：营养级种群动态由物种性状所决定，本研究以陆生节肢动物群落为研究对象展开相关探究。我们以异速营养网络（Allometric Trophic Network, ATN）模型为出发点，提出假说：若要更精准地模拟营养级相互作用，除体质量外，还需纳入栖息地利用特征。据此，我们在ATN模型中新增了能够描述微生境利用，以及种内与种间干扰的参数项。我们设计了实验与高效的采样方案，以检验该模型，以及关于主导营养级相互作用的性状的核心假设。我们最终制定了一套详细的采样方案，以最大化实验所得经验数据的信息含量；同时依托所提模型的理论分析，探究本实验设计可能存在的缺陷。综上，由于本项工作属于"实验前"研究，旨在优化假说构建、模型搭建、实验设计与数据采集之间的衔接逻辑，我们赶在分析实际实验数据前先行发表本研究成果，为后续开展强推断研究奠定基础。