Data from: Sampling beetle communities: trap design interacts with weather and species traits to bias capture rates

Globally, many insect populations are declining, prompting calls for action. Yet these findings have also prompted discussion about sampling methods and interpretation of long-term datasets. As insect monitoring and research efforts increase, it is critical to quantify the effectiveness of sampling methods. This is especially true if sampling biases of different methods covary with climate, which is also changing over time. We assess the effectiveness of two types of flight intercept traps commonly used for beetles, a diverse insect group responsible for numerous ecosystem services, under different climatic conditions in Norwegian boreal forest. One of these trap designs includes a device to prevent rainwater from entering the collection vial, diluting preservatives and flushing out beetles. This design is compared to a standard trap. We ask how beetle capture rates vary between these traps, and how these differences vary based on precipitation levels and beetle body size, an important species trait. Bayesian mixed models reveal that the standard and modified traps differ in their beetle capture rates, but that the magnitude and direction of these differences change with precipitation levels and beetle body size. At low rainfall levels standard traps catch more beetles, but as precipitation increases the catch rates of modified traps overtake those of standard traps. This effect is most pronounced for large-bodied beetles. Sampling methods are known to differ in their effectiveness. Here, we present evidence for a less well-known but likely common phenomenon - an interaction between climate and sampling, such that relative effectiveness of trap types for beetle sampling differs depending on precipitation levels and species traits. This highlights a challenge for long-term monitoring programs, where both climate and insect populations are changing. Sampling methods should be sought that eliminate climate interactions, any biases should be quantified, and all insect datasets should include detailed methodological metadata.全球范围内，诸多昆虫种群正持续衰减，这一现象引发了采取保护行动的呼吁。然而相关研究结果也引发了关于采样方法以及长期数据集解读的广泛讨论。随着昆虫监测与研究工作的不断推进，量化不同采样方法的有效性显得尤为关键。当不同采样方法的偏差与随时间变化的气候条件存在共变关系时，这一点更是至关重要。本研究在挪威北方针叶林的不同气候条件下，针对两类常用于甲虫（一类提供诸多生态系统服务功能的多样昆虫类群）的飞行拦截诱捕器的有效性展开评估。其中一款诱捕器设计配备了防止雨水进入收集瓶的装置，可避免防腐剂被稀释以及甲虫被冲出。本研究将该改良型诱捕器与标准型诱捕器进行对比。本研究旨在探究两类诱捕器的甲虫捕获率存在何种差异，以及这些差异如何随降水量水平和甲虫体型（一类重要的物种性状）发生变化。贝叶斯混合模型（Bayesian mixed models）结果显示，标准型与改良型诱捕器的甲虫捕获率存在显著差异，且此类差异的幅度与方向会随降水量水平以及甲虫体型发生变化。在低降水量条件下，标准型诱捕器的捕获量更高；但随着降水量增加，改良型诱捕器的捕获率会反超标准型诱捕器。该效应在大体型甲虫群体中表现最为显著。学界已知不同采样方法的有效性存在差异。本研究为一种尚未被广泛认知但实则可能普遍存在的现象提供了实证依据——即气候与采样方法之间存在交互效应：针对甲虫采样的不同诱捕器类型的相对有效性，会随降水量水平与物种性状发生变化。这一发现为长期监测项目带来了新的挑战——此类项目中气候与昆虫种群均处于动态变化之中。因此，亟需研发可消除气候交互效应的采样方法，同时需量化各类采样偏差，且所有昆虫数据集均应包含详尽的方法学元数据（methodological metadata）。