Anthropogenic impact can alter food web structure through changes in species interactions. In this study, we explored the food web of three Mediterranean stream reaches (two seasonal and one permanent) along an anthropogenic impact gradient to test the hypothesis that increasing impact simplifies food webs. To test this, we applied the isotopic (δ 13 C and δ 15 N) niche concept to compare reaches using isotopic metrics (isotopic richness, divergence, dispersion, evenness, and redundancy). The isotopic indices were useful to identify differences in food web architecture among the three reaches. The least impacted site had the highest isotopic richness, dispersion, and isotopic redundancy, suggesting higher ecological resilience at this site. The effect of disturbance in the remaining two sites was masked by the presence of invasive crayfish, which increased isotopic divergence and was responsible for higher food-chain length in the most impacted reach, but not in the moderately impacted reach. Consumers displayed generalistic feeding habits, with Bayesian mixing models indicating that they relied primarily on a mixture of periphyton, other macroinvertebrates, and to a lesser extent, detritus. Some taxa displayed changes in their dietary habitats depending on the site, indicating that the same type of taxa fed on distinct foods at each stream reach.

中文翻译：

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三个地中海河流的食物网结构沿着人为影响的梯度到达

人为影响可以通过物种相互作用的变化来改变食物网结构。在这项研究中，我们沿着人为影响梯度探索了三个地中海河流河段（两个季节性和一个永久性）的食物网，以测试影响增加简化食物网的假设。为了测试这一点，我们应用同位素（δ 13 C 和δ 15 N）生态位概念来比较使用同位素指标（同位素丰富度、发散度、分散度、均匀度和冗余度）的河段。同位素指数有助于确定三个河段之间食物网结构的差异。受影响最小的站点具有最高的同位素丰富度、分散度和同位素冗余度，表明该站点具有更高的生态恢复力。其余两个地点的干扰影响被侵入性小龙虾的存在所掩盖，这增加了同位素差异，并导致受影响最严重的地区的食物链长度更长，但在中等影响的地区则不然。消费者表现出普遍的饮食习惯，贝叶斯混合模型表明他们主要依赖附生生物和其他大型无脊椎动物的混合物，在较小程度上依赖碎屑。一些分类群的饮食栖息地因地点而异，这表明同一类型的分类群以不同的食物为食，在每条河流到达。碎屑。一些分类群的饮食栖息地因地点而异，这表明同一类型的分类群以不同的食物为食，在每条河流到达。碎屑。一些分类群的饮食栖息地因地点而异，这表明同一类型的分类群以不同的食物为食，在每条河流到达。