Climate change is altering the water cycle globally, increasing the frequency and magnitude of floods and droughts. An outstanding question is whether biodiversity responses to hydrological disturbance depend on background climatic context – and if so, which contexts increase vulnerability to disturbance. Answering this question requires comparison of organismal responses across environmental gradients. However, opportunities to track disturbed communities against an undisturbed baseline remain rare. Here we gathered a global dataset capturing responses of aquatic invertebrate communities to river drying, which includes 112 sites spanning a gradient of climatic aridity. We measured the effects of river drying on taxonomic richness and temporal β-diversity (turnover and nestedness components). We also measured the relative abundance of aquatic invertebrates with strategies that confer resilience (or resistance) to drying. Contrary to our expectations, we found that taxonomic richness recovered from drying similarly across the aridity gradient. The turnover component of β-diversity (i.e. species replacements over time) largely accounted for differences in community composition before versus after drying. However, increasing aridity was associated with greater nestedness-driven compositional changes at intermittent sites – that is, after drying communities became subsets of those before drying. These results show that climatic context can explain variation in community responses to the same hydrological disturbance (drying), and suggest that increased aridity will constrain biodiversity responses at regional scales. Further consideration of the climatic context in hydroecological research may help improve predictions of the local impacts of hydrological disturbance by identifying climate regions where communities are more (or less) sensitive to extremes, including river drying events.

中文翻译：

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气候干旱增加了自然干涸河流中无脊椎动物群落的时间嵌套

气候变化正在改变全球的水循环，增加了洪水和干旱的频率和规模。一个悬而未决的问题是，生物多样性对水文干扰的反应是否取决于背景气候环境——如果是，哪些环境会增加对干扰的脆弱性。回答这个问题需要比较不同环境梯度的生物体反应。然而，根据未受干扰的基线跟踪受干扰社区的机会仍然很少。在这里，我们收集了一个全球数据集，捕捉水生无脊椎动物群落对河流干涸的反应，其中包括跨越气候干旱梯度的 112 个地点。我们测量了河流干涸对分类丰富度和时间 β 多样性（周转和嵌套分量）的影响。我们还测量了水生无脊椎动物的相对丰度，这些策略赋予了对干燥的弹性（或抵抗力）。与我们的预期相反，我们发现在干旱梯度上，分类丰富度从干燥中恢复。β 多样性的周转成分（即物种随时间的替换）在很大程度上解释了干燥前后群落组成的差异。然而，干旱的增加与间歇性地点更大的嵌套驱动的组成变化有关——也就是说，在干燥后群落成为干燥前群落的子集。这些结果表明，气候环境可以解释社区对相同水文干扰（干燥）反应的变化，并表明干旱增加将限制区域尺度的生物多样性反应。