A major goal in ecology is to understand mechanisms that influence patterns of biodiversity and community assembly at various spatial and temporal scales. Understanding how community composition is created and maintained also is critical for natural resource management and biological conservation. In this study, we investigated environmental and spatial factors influencing beta diversity of local fish assemblages along the longitudinal gradient of a nearly pristine Neotropical river in the Colombian Llanos. Standardized surveys were conducted during the low-water season at 34 sites within the Bita River Basin. Physical, chemical and landscape parameters were recorded at each site, and asymmetric eigenvector maps were used as spatial variables. To examine the relative influence of dispersal and environmental variables on beta diversity and its components, distance-based redundancy analysis (db-RDA) and variation partitioning analysis were conducted. We proposed that spatial scale of analysis and position within the river network would constrain patterns of beta diversity in different ways. However, results indicated that in this system, high beta diversity was consistent among species assemblages no matter the scale of analysis or position within the river network. Species replacement (turnover) dominated beta diversity, an indication of the importance of species sorting. These findings suggested that conservation of fish diversity in tropical rivers requires maintenance of both habitat heterogeneity (spatial variation in habitat conditions) and connectivity at the scale of entire river basins.

中文翻译：

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局部环境因素对热带鱼组合的β多样性模式的影响大于空间因素

生态学的一个主要目标是了解在不同时空尺度上影响生物多样性和群落组装模式的机制。了解如何创建和维护社区组成对于自然资源管理和生物保护也至关重要。在这项研究中，我们调查了影响哥伦比亚利亚诺斯一条近乎原始的新热带河流纵向梯度的当地鱼类组合的 beta 多样性的环境和空间因素。在缺水季节在碧塔河流域内的 34 个地点进行了标准化调查。在每个站点记录物理、化学和景观参数，并使用非对称特征向量图作为空间变量。为了检查散布和环境变量对 beta 多样性及其组成部分的相对影响，进行了基于距离的冗余分析 (db-RDA) 和变异分区分析。我们提出，分析的空间尺度和河网内的位置将以不同的方式限制贝塔多样性的模式。然而，结果表明，在该系统中，无论分析规模或河网位置如何，物种组合之间的高贝塔多样性是一致的。物种替换（周转）主导了 Beta 多样性，这表明物种分类的重要性。