Data from: Direct and plant trait-mediated effects of the local environmental context on butterfly oviposition patterns

Variation in the intensity of plant-animal interactions over different spatial scales is widespread and might strongly influence fitness and trait selection in plants. Differences in traits among plant individuals have been shown to influence variation in interaction intensities within populations, while differences in environmental factors and community composition are shown to be important for variation over larger scales. However, little is still known about the relative importance of the local environmental context vs. plant traits for the outcome of interactions within plant populations. We investigated how oviposition by the seed-predator butterfly Phengaris alcon on its host plant Gentiana pneumonanthe was related to host plant traits and to local environmental variation, as well as how oviposition patterns translated into effects on host plant fruit set. We considered the local environmental context in terms of height of the surrounding vegetation and abundance of the butterfly’s second host, Myrmica ants. The probability of oviposition was higher in plants that were surrounded by lower vegetation, and both the probability of oviposition and the number of eggs increased in early-flowering and tall plants with many flowers in the three study populations. Flowering phenology, shoot height and flower production were, in turn, related to higher surrounding vegetation. Myrmica abundance was correlated with vegetation height, but had no effect on oviposition patterns. Oviposition and subsequent seed predation by the caterpillars strongly reduced host plant fruit set. Our results show that plant-animal interactions are context-dependent not only because the context influences the abundance or the behavior of the animal interactor, but also because it influences the expression of plant traits that affect the outcome of the interaction. The results also demonstrate that heterogeneity in environmental conditions at a very local scale can be important for the outcomes of interactions.

植物-动物互作（plant-animal interactions）在不同空间尺度上的强度变异广泛存在，且可能对植物的适合度与性状选择产生强烈影响。已有研究证实，植物个体间的性状差异会影响种群内部互作强度的变异，而环境因子与群落组成的差异则对更大尺度上的变异具有关键作用。然而，目前对于局域环境背景与植物性状在植物种群内互作结局中的相对重要性，仍缺乏足够的认知。

本研究以种子捕食性蝴蝶——大蓝蝶（Phengaris alcon）在其宿主植物沼生龙胆（Gentiana pneumonanthe）上的产卵行为为研究对象，探究其与宿主植物性状、局域环境变异的关联，以及产卵模式如何对宿主植物坐果率产生影响。本研究从周围植被高度以及该蝴蝶第二宿主红蚁属（Myrmica）蚂蚁的多度两个维度，对该局域环境背景进行考量。

研究结果显示：被低矮植被环绕的宿主植物更易被产卵；在三个研究种群中，早开花、株型高大且花朵数量较多的植物，其产卵概率与卵粒数量均显著更高。进一步分析表明，周围植被高度越高，植物的开花物候、株高与花生产量越高。红蚁属蚂蚁的多度与植被高度呈正相关，但对产卵模式无显著影响。产卵行为及后续幼虫的种子捕食行为，会显著降低宿主植物的坐果率。

本研究结果表明，植物-动物互作的环境依赖性不仅源于环境背景会影响动物互作者的多度或行为，还源于其能够调控影响互作结局的植物性状表达。同时，研究证实极局域尺度上的环境条件异质性，对互作结局同样具有重要意义。