Timoner Pablo, Marle Pierre, Castella Emmanuel, Lehmann Anthony
enviroSPACE Group, Department F.-A. Forel for Environmental and Aquatic Sciences Institute for Environmental Sciences, University of Geneva Geneva Switzerland.
Aquatic Ecology Group, Department F.-A. Forel for Environmental and Aquatic Sciences Institute for Environmental Sciences, University of Geneva Geneva Switzerland.
Ecol Evol. 2022 Aug 4;12(8):e9135. doi: 10.1002/ece3.9135. eCollection 2022 Aug.
-Diversity, commonly defined as the compositional variation among localities that links local diversity (-diversity) and regional diversity (-diversity), can arise from two different ecological phenomena, namely the spatial species turnover (i.e., species replacement) and the nestedness of assemblages (i.e., species loss). However, any assessment that does not account for stochasticity in community assembly could be biased and misinform conservation management. In this study, we aimed to provide a better understanding of the overall ecological phenomena underlying stream -diversity along elevation gradients and to contribute to the rich debate on null model approaches to identify nonrandom patterns in the distribution of taxa. Based on presence-absence data of 78 stream invertebrate families from 309 sites located in the Swiss Alpine region, we analyzed the effect size of nonrandom spatial distribution of stream invertebrates on the -diversity and its two components (i.e., turnover and nestedness). We used a modeling framework that allows exploring the complete range of existing algorithms used in null model analysis and assessing how distribution patterns vary according to an array of possible ecological assumptions. Overall, the turnover of stream invertebrates and the nestedness of assemblages were significantly lower and higher, respectively, than the ones expected by chance. This pattern increased with elevation, and the consistent trend observed along the altitudinal gradient, even in the most conservative analysis, strengthened our findings. Our study suggests that deterministic distribution of stream invertebrates in the Swiss Alpine region is significantly driven by differential dispersal capacity and environmental stress gradients. As long as the ecological assumptions for constructing the null models and their implications are acknowledged, we believe that they still represent useful tools to measure the effect size of nonrandom spatial distribution of taxa on -diversity.
多样性通常被定义为连接局部多样性（α多样性）和区域多样性（γ多样性）的不同地点间的组成变化，它可能源于两种不同的生态现象，即空间物种更替（即物种替代）和群落嵌套性（即物种丧失）。然而，任何未考虑群落组装过程中随机性的评估都可能存在偏差，并误导保护管理工作。在本研究中，我们旨在更好地理解沿海拔梯度的溪流α多样性背后的整体生态现象，并为关于识别分类单元分布中非随机模式的零模型方法的丰富辩论做出贡献。基于瑞士阿尔卑斯地区309个地点的78个溪流无脊椎动物科的存在-缺失数据，我们分析了溪流无脊椎动物非随机空间分布对α多样性及其两个组成部分（即更替和嵌套性）的效应大小。我们使用了一个建模框架，该框架允许探索零模型分析中使用的现有算法的完整范围，并评估分布模式如何根据一系列可能的生态假设而变化。总体而言，溪流无脊椎动物的更替和群落的嵌套性分别显著低于和高于随机预期值。这种模式随海拔升高而增加，并且即使在最保守的分析中，沿海拔梯度观察到的一致趋势也强化了我们的研究结果。我们的研究表明，瑞士阿尔卑斯地区溪流无脊椎动物的确定性分布显著受不同扩散能力和环境压力梯度的驱动。只要承认构建零模型的生态假设及其含义，我们相信它们仍然是衡量分类单元非随机空间分布对α多样性效应大小的有用工具。
