1. Human impacts on aquatic ecosystems are causing shifts in the composition and distribution of species, leading to subsequent changes in community structure. However, these changes may not be fully realised because of inadequate baseline information. In Texas, such baseline information is generally lacking for cryptic aquatic species such as unionid mussels, which will be likely to impede identification of impacted populations, potential causal factors, and the setting or achieving of management goals.
2. The Navasota River, located in central Texas, is an exception, having been comprehensively surveyed more than 40 years ago, prior to large‐scale impoundment of this system. Hierarchical cluster analysis, nonmetric multidimensional scaling, and fuzzy set ordination were performed to compare assemblage structure from the 1975 survey to that of a recent survey in 2016 at similar sampling locations.
3. Comparing sites based on the presence–absence of mussel species, we found no significant differences between the number of taxa and species present; however, we did find significant filtering of mussel life history strategies. Specifically, prior to impoundment, we found that mussel assemblages were filtered based on longitudinal patterns in life history strategy from taxa that are adapted to disturbed habitats to those favoured in more stable habitats with low environmental variation.
4. However, following large‐scale impoundment after 1975, we saw a shift in the hydrologic regime towards consistent, homogenised flows and a shift in assemblage structure towards equilibrium species. This shift appears to represent a discontinuity, wherein river impoundment alters physical parameters of the hydrologic regime and these changes in turn modify biotic patterns and processes.
5. Our results provide another example of how large dams can restructure mussel assemblages, highlight the importance of incorporating reference or baseline conditions wherever possible when evaluating the conservation status of aquatic biota, and provide further evidence for the use of life history theory and the serial discontinuity concept in predicting the consequences of flow alteration and river impoundment.

中文翻译：

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将生活史策略和历史基线信息联系起来，可以显示出水流方式和蓄水池变化对淡水贻贝组合的影响

1. 人类对水生生态系统的影响导致物种组成和分布的变化，从而导致社区结构的后续变化。但是，由于基线信息不足，这些更改可能无法完全实现。在得克萨斯州，通常缺乏诸如联合贻贝这样的隐性水生物种的基线信息，这很可能会阻碍对受影响种群的识别，潜在的因果因素以及管理目标的设定或实现。
2. 位于得克萨斯州中部的纳瓦索塔河是一个例外，在对该系统进行大规模蓄水之前，已经进行了40多年的全面调查。进行了层次聚类分析，非度量多维标度和模糊集排序，以比较1975年调查与2016年最近一次调查在相似采样位置的组合结构。
3. 根据贻贝物种的存在与否比较站点，我们发现分类单元的数量与存在的物种之间没有显着差异。但是，我们确实发现了贻贝生活史策略的重要过滤条件。具体而言，在蓄水之前，我们发现贻贝组合是根据生命历史策略中的纵向模式从适应受干扰的栖息地的分类单元筛选到环境变化较小，更稳定的栖息地的筛选依据。
4. 但是，在1975年以后大规模蓄水之后，我们看到了水文体制向一致，均匀流动的转变，而集结结构向平衡物种的转变。这种转变似乎代表了一种不连续性，其中河流蓄水改变了水文状况的物理参数，而这些变化又改变了生物形态和过程。
5. 我们的结果提供了另一个示例，说明大型水坝如何重组贻贝组合，突出了评估水生生物保护状况时尽可能纳入参考条件或基准条件的重要性，并为使用生命史理论和系列间断性概念提供了进一步的证据。预测流量变化和河流蓄水的后果。