1. Metacommunity ecology includes connectivity in the investigation of local and regional processes to understand community assembly. The elements of metacommunity structure (EMS) framework classifies metacommunities into categorical archetypes based on patterns of three metrics indexing β diversity: coherence, turnover, and boundary clumping. Although the EMS framework is most commonly used to classify metacommunity types, an elements-based approach of examining how factors affect each specific continuous EMS variable could provide a more mechanistic understanding of how metacommunities are structured at the landscape scale. Moreover, few studies have sought to quantify how methodological issues such as number and spacing of local communities affect observed outcomes of EMS-based analyses.
2. Using a large dataset of stream fish occurrences in the eastern U.S.A., we used mixed effects models to investigate how (1) landscape-scale variables and (2) methodological issues such as number and location of sampling sites affect coherence, turnover, and boundary clumping individually; as well as (3) how landscape-scale variables influence overall metacommunity patterns derived from the EMS framework.
3. Coherence, turnover, and boundary clumping were related to temperature, density of dams, developed land use, and γ diversity. Interestingly, distance among sampled sites in metacommunities negatively affected turnover, and the number of sampling sites positively affected all three variables. Elevation affected overall observed metacommunity patterns, with metacommunities transitioning from Clementsian to clumped species loss patterns with increasing elevation.
4. Our results suggest that metacommunity structure is affected by both natural and anthropogenic landscape-scale variables. Observed metacommunity properties are also influenced by sampling density and site location within the catchment. Accounting for important natural, anthropogenic, and methodological issues will be critical for improving the inferential power of metacommunity analyses to begin understanding which landscape-scale variables should be the focus of conservation and management of fish communities at a catchment scale.

中文翻译：

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景观特征和研究设计影响美国东部河流鱼类元群落结构的要素

1. 元社区生态学包括调查当地和区域过程以了解社区组装的连通性。元社区结构 (EMS) 框架的元素根据索引 β 多样性的三个指标模式将元社区分类为分类原型：连贯性、周转率和边界聚集。尽管 EMS 框架最常用于对元社区类型进行分类，但一种基于元素的方法来检查因素如何影响每个特定的连续 EMS 变量，可以提供对元社区如何在景观尺度上构建的更机械的理解。此外，很少有研究试图量化方法论问题，例如当地社区的数量和间隔如何影响基于 EMS 的分析的观察结果。
2. 使用美国东部河流鱼类出现的大型数据集，我们使用混合效应模型来研究 (1) 景观尺度变量和 (2) 方法论问题，例如采样点的数量和位置如何影响连贯性、周转率和边界聚集个人；以及 (3) 景观尺度变量如何影响源自 EMS 框架的整体元社区模式。
3. 连贯性、周转和边界聚集与温度、水坝密度、发达的土地利用和 γ 多样性有关。有趣的是，元社区中采样点之间的距离对营业额产生负面影响，而采样点的数量对所有三个变量都有正面影响。海拔影响了整体观察到的元群落模式，元群落随着海拔的增加从 Clementsian 过渡到成群的物种丧失模式。
4. 我们的结果表明元群落结构受自然和人为景观尺度变量的影响。观察到的元群落属性也受到流域内采样密度和站点位置的影响。考虑重要的自然、人为和方法问题对于提高元群落分析的推理能力至关重要，以开始了解哪些景观尺度变量应该成为流域尺度鱼类群落保护和管理的重点。