Data from: Drying determines the temporal dynamics of stream invertebrate structural and functional beta diversity

Assembly processes shaping ecological communities can vary over time
following variations of environmental conditions at different scales. Such
temporal dynamism is exacerbated by climate change and increasing extreme
events, and recent evidence suggests that, in turn, community composition
and functions can vary substantially. However, empirical relationships
between the spatio-temporal dynamics of communities and that extreme
events altering ecosystems are poorly investigated. We quantified the
temporal dynamics of stream invertebrate communities over two years across
11 river basins prone to drying, covering a large geographical area of
France. We tested predictions on the influence of the spatial arrangement
and temporal dynamics of drying events across river networks. Combining a
high temporal resolution of community description from taxonomic and
functional perspectives, we quantified beta diversity over time and space
and partitioned them into additive components: replacement of taxa and
richness difference. Frequency and duration of drying events were
precisely quantified and basins were classified based on the location of
the drying events. We found a strong influence of the spatial drying
pattern on the dissimilarities of community composition between sites. The
high temporal variability of community structure was directly related to
the frequency and duration of drying events. This temporal dynamism of
communities was also strongly affected by the spatial drying pattern,
indicating that fragmentation had a stronger effect on recolonisation
processes for upstream-drying basins. Finally, biological traits were
unevenly distributed in space and time, suggesting a lack of functional
redundancy that could have strong implications for ecosystem functions and
services. The high temporal dynamics of communities highlighted in this
study challenge the current definition of reference conditions in
intermittent rivers, and the community sensitivity to frequency and
duration of drying suggest that climate change might lead community
dynamics to be increasingly driven by stochastic environmental
variability.

塑造生态群落的组装过程会随时间变化，其变化规律遵循不同尺度下环境条件的波动。这种时间动态因气候变化和极端事件增多而加剧，近期证据表明，群落组成与功能也会相应发生显著变化。然而，群落的时空动态与改变生态系统的极端事件之间的实证关系研究不足。我们量化了法国大片地理区域内11个易干涸河流流域中溪流无脊椎动物群落（stream invertebrate communities）两年间的时间动态。我们检验了关于河流网络中干涸事件的空间分布格局及时空动态影响的预测。结合分类学与功能视角下高时间分辨率的群落描述，我们量化了时空尺度上的β多样性（beta diversity），并将其划分为可加性组分：类群更替与丰富度差异。我们精确量化了干涸事件的频率与持续时间，并基于干涸事件的发生位置对流域进行分类。研究发现，空间干涸格局对不同位点群落组成的差异具有显著影响。群落结构的高时间变异性与干涸事件的频率及持续时间直接相关。群落的这种时间动态还受空间干涸格局的强烈影响，表明碎片化对上干涸流域的再定居过程具有更强的作用。最后，生物性状在时空上分布不均，提示功能冗余的缺乏可能对生态系统功能与服务产生重大影响。本研究揭示的群落高时间动态挑战了间歇性河流参考状态的现有定义，而群落对干涸事件频率与持续时间的敏感性表明，气候变化可能导致群落动态日益受随机环境变异驱动。