Predation and parasitism on herbivorous insects change in opposite directions in a latitudinal gradient crossing a boreal forest zone

The Latitudinal Biotic Interaction Hypothesis (LBIH) predicts that the strength of various biotic interactions decreases from low to high latitudes. Inconsistency between studies testing this hypothesis may result from variations among different types of interactions and among study systems. Therefore, exploration of multiple interactions within one system would help to disentangle latitudinal patterns across individual interactions and to evaluate latitudinal changes in the overall impact of enemies on prey.
We tested the prediction based on the LBIH that the pressure of natural enemies on herbivorous insects decreases with an increase in latitude across the boreal forest zone. We also asked whether the impacts of major groups of these enemies exhibit similar latitudinal patterns and whether these patterns are consistent across study years. 
In 10 forest sites located from 60°N to 69°N in Northern Europe, each summer, from 2016–2019, we measured (i) mortality of three groups of leafmi..., The data are of three types: (1) mortality of leafminers: three data filed and three metadata files; (2) bird attack rates on artificial prey: one data file and one metadata file; and (3) herbivory on birches: one data file and one metadata file.
 1. Mortality of leafminers
We collected birch leaves mined by the larvae of Eriocrania spp. (between 10 and 29 June) and Stigmella spp. (between 8 and 29 August), and rowan leaves mined by the larvae of several moth species (between 8 and 29 August); sampling was conducted at each of our study sites annually from 2016‒2019. The same experienced persons searched for the mined leaves at all sites and during all study years. All discovered mines had been collected; we attempted to obtain 20–50 mines of each of three groups of moths from each study site annually. The samples were classified as either empty mines left by larvae which had successfully completed their development (i.e. survived individuals) or mines containing dead larvae or mines th...,

纬度生物相互作用假说（Latitudinal Biotic Interaction Hypothesis, LBIH）预测，各类生物相互作用的强度会随纬度从低到高逐渐降低。当前检验该假说的研究结论存在不一致，这可能源于不同相互作用类型以及研究系统间的差异。因此，在同一研究系统中探究多种生物相互作用，将有助于厘清单个相互作用的纬度分布模式，并评估天敌对猎物的整体影响随纬度的变化情况。

我们基于纬度生物相互作用假说，检验了“北方针叶林带内，天敌对植食性昆虫的压力随纬度升高而降低”这一预测。同时我们还探讨了两类问题：一是这类天敌的主要类群其影响是否呈现相似的纬度模式，二是这些模式在不同研究年份间是否保持一致。

2016至2019年的每个夏季，我们在北欧北纬60°至69°的10个森林样地中开展研究。本数据集包含三类数据：(1) 潜叶蛾死亡率：3份数据文件与3份元数据文件；(2) 人工猎物的鸟类捕食率：1份数据文件与1份元数据文件；(3) 桦树植食危害程度：1份数据文件与1份元数据文件。

1. 潜叶蛾死亡率
我们分别于6月10日至29日采集被Eriocrania属幼虫蛀食的桦树叶，于8月8日至29日采集被Stigmella属幼虫蛀食的桦树叶，同时采集同期被多种蛾类幼虫蛀食的花楸树叶；2016至2019年每年均在所有研究样地开展上述采样工作。所有采样均由同批经过专业培训的人员在各站点及各年度完成，以保证采样标准统一。我们收集所有发现的蛀叶虫道，每年计划从每个研究样地的三类蛾类类群中各采集20至50个虫道。采集的样本将被分为两类：一类是幼虫成功完成发育后遗留的空虫道（即存活个体的痕迹），另一类是含有死亡幼虫的虫道或……