1. In many mountainous areas, glaciers feed streams characterised by harsh environmental conditions, such as low water temperature, high turbidity, low channel stability, and high temporal variability in flow. Additionally, in many glacierised catchments, the mixture of streams arising from different water sources (glacier melt, groundwater, rainfall) generates high levels of environmental heterogeneity, which enhance species turnover rates and increase regional diversity.
2. Studies from mainly temperate regions have revealed some consistent patterns: a predominance of traits adaptive to harsh environmental conditions and reduced functional diversity with increased glaciality, both strongly related to environmental filtering. Here, we investigated variation in functional structure and diversity between macroinvertebrate communities from 15 stream sites, with different water sources (five glacier‐fed, five groundwater‐fed, and five mixed source) and level of glacier influence, in a glacierised catchment in the Ecuadorian Andes.
3. Our results revealed functional differences between communities inhabiting the different stream types. As found in temperate regions, high levels of glaciality were associated with an increase of small‐sized taxa that do not swim but are temporarily attached to or burrow in the substrate, have a flying‐adult stage, and feed by collecting–gathering. Similarly, we found a general decrease in functional diversity at sites with higher glacier influence. A null modelling approach suggested that in some of our glacier‐fed sites, environmental filtering may be the main driver of community assembly, whereas other mechanisms, mainly regional (such as dispersal), but also local (such as intraspecific competition), may gain importance as glacier influence decreases.
4. Assemblage composition in streams in tropical glacierised catchments may be driven by both local and regional processes that generate a gradient of decreasing functional diversity with stronger glacier influence. However, lack of knowledge of relevant traits for taxa in tropical glacierised streams currently poses a substantial obstacle to predicting changes likely to arise from global warming and glacier melt in this region.

中文翻译：

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热带安第斯山脉冰川集水区无脊椎动物群落的功能结构和多样性

1. 在许多山区，冰川供给的水流具有苛刻的环境条件，例如低水温，高浊度，低河道稳定性和高流量随时间变化。此外，在许多冰川化的流域，不同水源（冰川融化，地下水，降雨）产生的水流混合会产生高水平的环境异质性，从而增加物种周转率并增加区域多样性。
2. 来自主要温带地区的研究揭示了一些一致的模式：适应恶劣环境条件的性状占优势，随着冰川的增加而功能多样性降低，这两者都与环境过滤密切相关。在这里，我们研究了来自15个河流站点，具有不同水源（五种冰川喂养，五种地下水喂养和五种混合水源）的大型无脊椎动物群落之间的功能结构和多样性变化以及冰川影响水平，该区域为冰川集水区。厄瓜多尔安第斯山脉。
3. 我们的结果表明，居住在不同溪流类型的社区之间的功能差异。如在温带地区发现的那样，高冰川度与小型类群的增加有关，这些类群不游泳，但暂时附着在基质上或在基质中钻洞，成虫成虫，并通过收集-收集来喂养。同样，我们发现冰川影响较高的地区功能多样性普遍下降。无效建模方法表明，在我们的某些冰川灌输站点中，环境过滤可能是社区聚集的主要驱动力，而其他机制，主要是区域性（例如分散），但也可能是局部性（例如种内竞争），冰川影响力降低的重要性。
4. 热带冰川集水区河流中的组合物组成可能受到局部和区域过程的驱动，这些过程会产生梯度下降的功能多样性，而冰川影响力更大。然而，目前缺乏对热带冰川流中分类单元相关性状的了解，对预测该地区全球变暖和冰川融化可能引起的变化构成了重大障碍。