Food webs show the architecture of trophic relationships, revealing the biodiversity and species interactions in an ecosystem. Understanding which factors modulate the structure of food webs offers us the ability to predict how they will change when influential factors are altered. To date, most of the research about food webs has focused on species interactions whereas the influences of surrounding environments have been overlooked. Here, using network analysis, we identified how the structure of aquatic food webs varied across a range of geophysical conditions within a whole stream system. Within a headwater basin in the Cascade Mountain Range, Oregon, USA, macroinvertebrate and vertebrate composition was investigated at 18 sites. Predator–prey interactions were compiled based on existing literature and dietary analysis. Several structural network metrics were calculated for each food web. We show that the structure of food webs was predictable based on geophysical features at both local (i.e., slope) and broader (i.e., basin size) spatial extents. Increased omnivory, greater connectance, shorter path lengths, and ultimately greater complexity and resilience existed downstream compared to upstream in the stream network. Surprisingly, the variation in food web structure was not associated with geographic proximity. Structural metric values and abundance of omnivory suggest high levels of stability for these food webs. There is a predictable variation in the structure of food webs across the network that is influenced by both longitudinal position within streams and patchy discontinuities in habitat. Hence, findings illustrate that the slightly differing perspectives from the River Continuum Concept, Discontinuity Patch Dynamics, and Process Domains can be integrated and unified using food web networks. Our analyses extend ecologists’ understanding of the stability of food webs and are a vital step toward predicting how webs and communities may respond to both natural disturbances and current global environmental change.

中文翻译：

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地球物理模板可调节杂食性占主导地位的河流食物网的结构

食物网显示了营养关系的体系结构，揭示了生态系统中的生物多样性和物种相互作用。了解哪些因素会调节食物网的结构，使我们能够预测当影响因素发生变化时食物网将如何变化。迄今为止，关于食物网的大多数研究都集中在物种相互作用上，而周围环境的影响却被忽略了。在这里，通过网络分析，我们确定了整个流系统中水生食物网的结构如何在一系列地球物理条件下发生变化。在美国俄勒冈州喀斯喀特山脉的上游水域内，对18个地点的大型无脊椎动物和脊椎动物组成进行了调查。捕食者与猎物之间的相互作用是根据现有文献和饮食分析编制的。为每个食物网计算了几个结构网络指标。我们表明，食物网的结构是基于地球物理特征在局部（即斜坡）和较宽（即盆地大小）空间范围内可预测的。与流网络中的上游相比，下游存在更多的杂食性，更大的连接性，更短的路径长度以及最终更大的复杂性和灵活性。令人惊讶的是，食物网结构的变化与地理邻近性无关。结构度量值和杂食性含量高，表明这些食物网具有很高的稳定性。整个网络中食物网的结构存在可预测的变化，受溪流中的纵向位置和栖息地中不连续的不连续性的影响。因此，研究结果表明，与河流连续体概念，间断斑块动力学和过程域的观点略有不同，可以使用食物网网络进行集成和统一。我们的分析扩展了生态学家对食物网稳定性的理解，是预测食物网和社区如何应对自然干扰和当前全球环境变化的重要一步。