Biotic homogenization represents a major concern in ecology but relatively few studies have assessed climate change impacts on assemblage patterns of freshwater species. Our main goals were to predict the current and future (years 2035, 2060 and 2085) patterns of mayfly, stonefly and caddisfly (EPT) diversity across Switzerland from macroscale environmental variables, and to assess the impact of warming temperatures on β‐diversity. The study area was the entire Swiss territory divided into 21 818 subcatchments (median area of 1.41 km2), used as spatial units for predicting patterns of EPT diversity. We assumed that the stream conditions were homogeneous within a subcatchment at this scale. Incidence of EPT larvae was derived from samplings carried out between 2010 and 2017 in 292 water‐course sites as part of two national monitoring programs. We employed generalized dissimilarity modeling to analyze the spatial turnover of EPT assemblages. Climatic, topographic, geological and land‐use variables were used as covariates, and different climate change scenarios were used for future predictions. We compared β‐diversity among the different scenarios through distance‐based tests of homogeneity of multivariate dispersions. Our findings showed the largest amount of EPT turnover occurred along the air temperature and slope gradients, considered as good proxies for water temperature and flow velocity. We predicted a biotic homogenization with increasing temperatures due to the upstream expansion of some species from the sub‐montane level, which only stabilizes in the most conservative climate scenario. This study is the first countrywide prediction of EPT composition patterns in the context of global warming and provides insights into the vulnerability of assemblages occurring at high elevations.

中文翻译：

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面对全球变暖，瑞士自来水中蜉蝣、石蝇和石螟的空间格局

生物同质化是生态学中的一个主要问题，但相对较少的研究评估了气候变化对淡水物种组合模式的影响。我们的主要目标是从宏观环境变量中预测瑞士目前和未来（2035、2060 和 2085 年）蜉蝣、石蝇和石蛾 (EPT) 多样性的模式，并评估气温升高对 β 多样性的影响。研究区域是整个瑞士领土，分为 21 818 个子汇水面积（中位数为 1.41 平方公里），用作预测 EPT 多样性模式的空间单位。我们假设河流条件在这个规模的子汇水面积内是均质的。EPT 幼虫的发生率来自 2010 年至 2017 年间在 292 个水道站点进行的采样，这是两个国家监测计划的一部分。我们采用广义相异模型来分析 EPT 组合的空间周转。气候、地形、地质和土地利用变量被用作协变量，不同的气候变化情景被用于未来预测。我们通过基于距离的多元分散同质性测试比较了不同场景中的 β 多样性。我们的研究结果表明，沿着气温和坡度梯度发生的 EPT 周转量最大，被认为是水温和流速的良好代表。我们预测，由于某些物种从亚山地水平向上游扩张，温度升高会导致生物同质化，这仅在最保守的气候情景中稳定下来。