Deterministic and stochastic processes are two major factors shaping community dynamics, but their relative importance remains unknown for many aquatic systems, including those in the high-elevation Qinghai–Tibet Plateau. Here, we explored the causes of multidimensional beta diversity patterns (i.e., taxonomic, functional, and phylogenetic) of a macroinvertebrate metacommunity in this large aquatic system by using multiple approaches (i.e., null models, phylogenetic signal testing, and ordination-based approaches). To obtain insights into community assembly mechanisms, we also analyzed beta diversity in two deconstructed sub-metacommunities (e.g., different tributaries and the main lake body). We found that most functional traits showed significant phylogenetic signals, indicating that the functional traits were profoundly influenced by evolutionary history. The null models showed randomness of functional and phylogenetic beta diversities for the whole basin and its tributaries, confirming the importance of stochasticity over deterministic processes in controlling community structure. However, both phylogenetic and functional community structures were clustered in the Qinghai Lake, probably reflecting the importance of environmental filtering. Ordination-based approaches also revealed that both environmental factors and spatial processes accounted for variation in taxonomic, functional, and phylogenetic beta diversity. More specifically, environmental filtering was more important than spatial processes for the functional dimension, but the opposite was true for the taxonomic and phylogenetic dimensions. The paleogeographic history of the Qinghai Lake basin may have contributed substantially to the prevalence of stochastic processes. Overall, this study provides a better understanding of ecological patterns and assembly mechanisms of macroinvertebrate communities across this poorly known high-elevation aquatic system that is highly sensitive to climate warming.

中文翻译：

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在高原水生系统中构建大型无脊椎动物群落时，随机性优先于确定性过程

确定性和随机过程是影响群落动态的两个主要因素，但对于许多水生系统，包括青藏高原高海拔的水生系统，它们的相对重要性仍然未知。在这里，我们通过使用多种方法（即无效模型、系统发育信号测试和基于排序的方法）探索了这个大型水生系统中大型无脊椎动物元群落的多维 beta 多样性模式（即分类、功能和系统发育）的原因. 为了深入了解社区组装机制，我们还分析了两个解构的子元社区（例如，不同的支流和主要湖体）中的 beta 多样性。我们发现大多数功能性状表现出显着的系统发育信号，表明功能性状受到进化历史的深刻影响。零模型显示了整个盆地及其支流的功能和系统发育 β 多样性的随机性，证实了随机性在控制群落结构方面对确定性过程的重要性。然而，青海湖的系统发育和功能群落结构都聚集在一起，这可能反映了环境过滤的重要性。基于排序的方法还表明，环境因素和空间过程都解释了分类学、功能和系统发育 beta 多样性的变化。更具体地说，环境过滤在功能维度上比空间过程更重要，但在分类学和系统发育维度上则相反。青海湖流域的古地理历史可能在很大程度上促成了随机过程的盛行。总体而言，这项研究提供了对大型无脊椎动物群落生态模式和组装机制的更好理解，该群落对气候变暖高度敏感的鲜为人知的高海拔水生系统。