Understanding the mechanisms that structure communities have been a major challenge in ecological theory. Functional trait-based approaches are increasingly used for studying the processes underlying community assembly. However, species-poor systems of Andean streams these processes are largely unknown. Tropical Andean streams are highly variable in space-time and characterised by the harsh or stable environment, resulting in a high taxonomic and ecological diversity. In this study, we tested the influence of environmental variables on the fish functional structure. We proposed that in ecosystems with harsh environments, environmental filtering will structure fish assemblages, and in ecosystems with a more stable environment, limiting similarity will prevail, increasing functional diversity. We analysed fish assemblages using functional diversity indices, fourth-corner RLQ analyses and multiple regression models. Environmental variables such as altitude, stream width, sub-Andean vegetation and pH influenced functional diversity. For instance, high values of functional redundancy were registered at high elevation streams, reflecting fish assemblages composed of highly dominant species with similar functional traits such as species of the genus Astroblepus. However, we found differences between Astroblepus species in the number and distance of gill rakers which might indicate resource partitioning and coexistence. On the other hand, our results show both stochastic dynamics and environmental filtering are structuring fish assemblages in low and high elevation Andean streams respectively.

中文翻译：

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是什么控制了哥伦比亚安第斯河流中的鱼类功能多样性模式？

了解构成群落的机制一直是生态学理论的一项重大挑战。基于功能特征的方法越来越多地用于研究社区组装的过程。然而，安第斯河流的物种贫乏系统这些过程在很大程度上是未知的。热带安第斯河流时空变化很大，环境恶劣或稳定，导致分类和生态多样性很高。在这项研究中，我们测试了环境变量对鱼类功能结构的影响。我们提出，在环境恶劣的生态系统中，环境过滤将构建鱼类组合，在环境更稳定的生态系统中，限制相似性将占主导地位，增加功能多样性。我们使用功能多样性指数、第四角 RLQ 分析和多元回归模型分析了鱼类组合。海拔、河流宽度、亚安第斯山脉植被和 pH 值等环境变量影响功能多样性。例如，在高海拔溪流中记录了高值的功能冗余，反映了由具有相似功能特征的高度优势物种组成的鱼类组合，例如该属的物种星鱼。然而，我们发现Astroblepus物种之间在鳃耙的数量和距离上存在差异，这可能表明资源划分和共存。另一方面，我们的结果表明，随机动力学和环境过滤分别在低海拔和高海拔安第斯河流中构建鱼类组合。