Linking mechanistic processes to the stability of ecological networks is a key frontier in ecology. In trophic networks, "modules"-groups of species that interact more with each other than with other members of the community-confer stability, mitigating effects of species loss or perturbation. Modularity, in turn, is shaped by the interplay between species' diet breadth traits and environmental influences, which together dictate interaction structure. Despite the importance of network modularity, variation in this emergent property is poorly understood in complex natural systems. Using two years of field data, we quantified interactions between a rich community of lepidopteran herbivores and their host plants across a mosaic of low-resource serpentine and high-resource nonserpentine soils. We used literature and our own observations to categorize herbivore species as generalists (feeding on more than one plant family) or specialists (feeding on one plant family). In both years, the plant-herbivore network was more modular on serpentine than on nonserpentine soils-despite large differences in herbivore assemblage size across years. This structural outcome was primarily driven by reduction in the breadth of host plant use by generalist species, rather than by changes in the composition of species with different fundamental diet breadths. Greater modularity-and thus greater stability-reflects environmental conditions and plastic responses by generalist herbivores to low host plant quality. By considering the dual roles of species traits and ecological processes, we provide a deeper mechanistic understanding of network modularity, and suggest a role for resource availability in shaping network persistence.

中文翻译：

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通才更专注于资源匮乏的栖息地，从而提高了生态网络结构的稳定性。

将机械过程与生态网络的稳定性联系起来是生态学的一个重要前沿领域。在营养网络中，“模块”-与社区中其他成员相比相互作用更多的物种组具有稳定性，从而减轻了物种丧失或干扰的影响。反过来，模块性是由物种的饮食广度特征和环境影响之间的相互作用所决定的，它们共同决定了相互作用的结构。尽管网络模块化非常重要，但是在复杂的自然系统中，这种新兴属性的变化却鲜为人知。利用两年的现场数据，我们量化了鳞翅目草食动物的丰富群落与其寄主植物在低资源蛇纹石和高资源非蛇纹石土壤上的相互作用。我们使用文献和我们自己的观察将草食动物物种分类为通才（以多个植物科目为食）或专家（以一个植物科目为食）。在这两年中，尽管多年以来草食动物组合的大小差异很大，但蛇纹石的植物-草食动物网络比非蛇纹石的土壤更具模块化。这种结构性结果主要是由于通才物种减少了寄主植物使用的广度，而不是由于具有不同基本饮食广度的物种组成的变化。更高的模块性（因此也更高的稳定性）反映了环境条件和通才食草动物对寄主植物质量低下的可塑性响应。通过考虑物种特征和生态过程的双重作用，我们提供了对网络模块化的更深层次的机械理解，