Trophic interactions may strongly depend on body size and environmental variation, but this prediction has been seldom tested in nature. Many spiders are generalist predators that use webs to intercept flying prey. The size and mesh of orb webs increases with spider size, allowing a more efficient predation on larger prey. We studied to this extent the orb-weaving spider Araneus diadematus inhabiting forest fragments differing in edge distance, tree diversity and tree species. These environmental variables are known to correlate to insect composition, richness and abundance. We anticipated these forest characteristics to be a principle driver of prey consumption. We additionally hypothesised them to impact spider size at maturity and expect shifts towards larger prey-size distributions in larger individuals independently from the environmental context. We quantified spider diet by means of metabarcoding of nearly 1000 A. diadematus from a total of 53 forest plots. This approach allowed a massive screening of consumption dynamics in nature, though at the cost of identifying the exact prey identity, as well as their abundance and putative intraspecific variation. Our study confirmed A. diadematus as a generalist predator, with more than 300 prey ZOTUs detected in total. At the individual level, we found large spiders to consume fewer different species, but adding larger species to their diet. Tree species composition affected both prey species richness and size in the spider's diet, although tree diversity per se had no influence on the consumed prey. Edges had an indirect effect on the spider diet as spiders closer to the forest edge were larger and therefore consumed larger prey. We conclude that both intraspecific size variation and tree species composition shape the consumed prey of this generalist predator.

中文翻译：

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体型和树木种类组成决定了居住在森林中的多面体捕食者中猎物消耗的变化

营养相互作用可能在很大程度上取决于人体大小和环境变化，但是这一预测在自然界中很少得到检验。许多蜘蛛都是通才的捕食者，它们使用网拦截飞行的猎物。球网的大小和网眼随着蜘蛛的大小而增加，从而可以更有效地捕食更大的猎物。我们在此程度上研究了织球蜘蛛Araneus diadematus栖息于边缘距离，树木多样性和树木种类不同的森林碎片中的情况。已知这些环境变量与昆虫的组成，丰富度和丰度相关。我们预计这些森林特征将成为猎物消费的主要驱动力。我们还假设它们会在成熟时影响蜘蛛的大小，并期望独立于环境而转向较大个体中更大的猎物大小分布。我们通过对总共53个森林地块中近1000个A. diadematus的metabarcode量化了蜘蛛的饮食。这种方法允许对自然界中的消费动态进行大规模筛选，尽管以识别确切的猎物身份以及它们的丰富度和假定的种内变异为代价。我们的研究证实了地盘曲霉是通才捕食者，总共发现了300多个猎物ZOTU。在个体层面上，我们发现大型蜘蛛消耗较少的不同物种，但在它们的饮食中增加了较大的物种。树种的组成会影响蜘蛛饮食中的猎物种类丰富度和大小，尽管树木的多样性本身对消耗的猎物没有影响。边缘对蜘蛛的饮食有间接的影响，因为靠近森林边缘的蜘蛛更大，因此消耗的猎物也更多。我们得出的结论是，种内大小变异和树种组成都影响着这种通才捕食者的消耗猎物。