Data from: Climate and leaf traits, not latitude, explain variation in plant‐herbivore interactions across a species’ range

1. Spatial variation in abiotic and biotic factors creates local contexts that influence the intensity of plant‐herbivore interactions. Some previous studies have accounted for the complexity of these interactions with latitudinal clines, while the absence of such clines in many other systems suggests other, often unknown, local community factors may instead explain the variation in herbivory across populations. 2. We investigated plant‐herbivore interactions across the entire range of a long‐lived tree (Quercus garryana), evaluating the relative importance of climate, latitude, population size, and insect feeding guilds in determining leaf phenotype and the extent and variation in insect herbivory. In this ecosystem, rain shadows create a nonlinear relationship between climate and latitude, allowing us to disentangle the effects of environmental factors. By performing similar analyses on trees grown in a common garden, we were able to assess the relative importance of environmental factors to leaf defence traits and herbivory. 3. Total herbivory varied significantly among populations, and was best explained by variation in spring precipitation, leaf traits, and tree population size, but not latitude. The relative importance of each of these factors changed over the growing season and with insect feeding guild. Conversely, damage in the common garden did not vary among trees from different origins when grown in a constant environment, leading us to believe variation in damage in natural populations is more likely the result of the local environments. 4. Leaf traits (trichome density and specific leaf area) varied significantly among populations, but neither showed an effect of latitude. Variation in both traits was best explained by tree size, and seasonal temperatures or precipitation. We found no variation in insect diversity among field populations, but abundance varied with mean summer precipitation and population size. 5. Synthesis: Seasonal precipitation consistently explained the geographic variation in the extent of herbivory to Q. garryana, while latitude and winter temperatures, factors that are commonly associated with latitudinal gradients in the intensity of species interactions, did not. Our findings highlight the importance of local climates and functional traits in shaping biotic interactions and intraspecific variation in plant‐insect interactions across large spatial scales.1. 非生物与生物因子（abiotic and biotic factors）的空间变异会塑造影响植物-植食者互作（plant-herbivore interactions）强度的局域环境。过往部分研究借助纬向梯度（latitudinal clines）阐释了这类互作的复杂性，但诸多其他生态系统中并无此类纬向梯度的存在，这表明其他往往尚不明确的局域群落因子，或许才是解释不同种群间植食程度差异的关键因素。 2. 本研究针对长寿乔木加里栎（Quercus garryana）的完整分布范围开展植物-植食者互作调查，评估气候、纬度、种群规模以及昆虫取食功能群（insect feeding guilds）在决定叶片表型、昆虫植食程度及其变异中的相对重要性。该生态系统中，雨影效应造就了气候与纬度间的非线性关系，使我们得以厘清各类环境因子的独立效应。通过对同质园（common garden）栽培的植株开展同类分析，我们得以评估环境因子对叶片防御性状（leaf defence traits）及植食程度的相对贡献。 3. 不同种群的总植食程度存在显著差异，其中春季降水量、叶片性状以及乔木种群规模的变异最能解释这一差异，而纬度则无显著关联。各因子的相对重要性随生长季进程以及昆虫取食功能群的不同而发生动态变化。与之相反，在同质园的统一环境下栽培时，不同起源地的植株所受植食损害并无显著差异，这使我们推断自然种群中植食损害的变异更可能源于局域环境的影响。 4. 不同种群的叶片性状——毛状体密度（trichome density）与比叶面积（specific leaf area）——存在显著差异，但二者均未表现出纬度效应。两类性状的变异均可通过乔木体型、季节温度或降水量得到最佳解释。我们未发现野外种群间昆虫多样性存在显著差异，但昆虫丰度随夏季平均降水量与种群规模发生变化。 5. 综合分析：季节性降水持续稳定地解释了加里栎植食程度的地理变异，而通常与物种种间互作强度纬向梯度相关的纬度与冬季温度则未表现出显著关联。本研究结果凸显了局域气候与功能性状在大空间尺度上塑造生物互作以及植物-昆虫互作种内变异（intraspecific variation）的关键意义。