Data from: How well can body size represent effects of the environment on demographic rates? Disentangling correlated explanatory variables

Demographic rates are shaped by the interaction of past and current environments that individuals in a population experience. Past environments shape individual states via selection and plasticity, and fitness-related traits (e.g. individual size) are commonly used in demographic analyses to represent the effect of past environments on demographic rates. We quantified how well the size of individuals captures the effects of a population's past and current environments on demographic rates in a well-studied experimental system of soil mites. We decomposed these interrelated sources of variation with a novel method of multiple regression that is useful for understanding nonlinear relationships between responses and multicollinear explanatory variables. We graphically present the results using area-proportional Venn diagrams. Our novel method was developed by combining existing methods and expanding upon them. We showed that the strength of size as a proxy for the past environment varied widely among vital rates. For instance, in this organism with an income breeding life history, the environment had more effect on reproduction than individual size, but with substantial overlap indicating that size encompassed some of the effects of the past environment on fecundity. This demonstrates that the strength of size as a proxy for the past environment can vary widely among life-history processes within a species, and this variation should be taken into consideration in trait-based demographic or individual-based approaches that focus on phenotypic traits as state variables. Furthermore, the strength of a proxy will depend on what state variable(s) and what demographic rate is being examined; that is, different measures of body size (e.g. length, volume, mass, fat stores) will be better or worse proxies for various life-history processes.种群动态速率（demographic rates）由种群个体所经历的过往与当前环境的交互作用共同塑造。过往环境通过自然选择与表型可塑性塑造个体状态，而适合度相关性状（fitness-related traits，例如个体体型）常被应用于种群动态分析，用于表征过往环境对种群动态速率的影响。本研究以一个被广泛研究的土壤螨类（soil mites）实验系统为研究对象，量化了个体体型能够在多大程度上反映种群过往与当前环境对种群动态速率的影响。研究采用一种可用于解析响应变量与多重共线性解释变量间非线性关系的新型多元回归方法，对这些相互关联的变异来源进行分解，并通过面积比例维恩图（area-proportional Venn diagrams）对结果进行可视化呈现。本研究的新型方法通过整合并拓展已有研究方法构建而成。研究表明，作为过往环境替代指标的个体体型，其效力在不同生命史速率（vital rates）间存在显著差异。例如，在这种采取收入型繁殖（income breeding）生活史策略的物种中，环境对繁殖的影响强于个体体型，但二者存在大量重叠，表明体型涵盖了过往环境对繁殖力（fecundity）的部分影响。这一结果说明，作为过往环境替代指标的体型，其效力在同一物种的不同生命史过程中存在显著差异；在以表型性状（phenotypic traits）作为状态变量（state variables）的基于性状的种群动态分析或基于个体的研究方法中，应当考虑这种差异。此外，替代指标的效力取决于所考察的状态变量与种群动态速率；换言之，不同的体型测量方式（例如体长、体积、体重、脂肪储备），针对不同生命史过程的替代效力各有优劣。