Data from: Ignoring spatial effects results in inadequate models for variation in littoral macroinvertebrate diversity

Studies focusing on the effects of spatial processes versus environmental filtering on aquatic metacommunities have so far been focused almost entirely on relatively isolated systems, such as sets of different lakes or streams. In contrast, metacommunity patterns and underlying processes within a single aquatic system have received less attention. In this study, we aimed to examine how strongly variations in different diversity indices are affected by spatial processes (dispersal) versus local environmental conditions (species sorting) within a large lake system. Modern biodiversity research focuses on multiple diversity facets because different indices may be uncorrelated within and between facets, and they may thus describe different phenomena. We investigated the relationship of littoral macroinvertebrate diversity with environmental and spatial factors using 10 indices of species, functional and taxonomic diversity. Using spatial factors as proxies of dispersal, we decomposed variation in diversity indices into fractions attributable to environmental and spatial factors. Our results highlighted generally equal or higher importance of spatial processes in controlling the variation in diversity indices when compared to local environmental variables. Local environmental conditions accounted for higher proportion of variation only in a single index (i.e. taxonomic diversity). These findings suggest that the effects of high dispersal rates (mass effects) may override the influences of local environmental conditions (species sorting) on the diversity in highly-connected aquatic system, such as large lakes and marine coastal systems. Our results further suggest that biodiversity assessment and environmental monitoring in highly-connected systems cannot rely solely on the idea of environmental control. We hence recommend that the roles of both environmental and spatial processes should be integrated in basic and applied ecological research of aquatic systems.

迄今为止，聚焦于空间过程（spatial processes）与环境过滤（environmental filtering）对水生集合群落（aquatic metacommunities）影响的研究，几乎完全集中在相对孤立的系统中，例如不同湖泊或溪流的组合。与之相对，单一水生系统内的集合群落格局及其潜在过程却鲜有关注。

本研究旨在探究大型湖泊系统中，不同多样性指数的变异受空间过程与局域环境条件影响的相对强度，其中空间过程对应扩散（dispersal），局域环境条件对应物种分选（species sorting）。现代生物多样性研究聚焦于多维度多样性（diversity facets），因为不同指数在维度内部及维度之间可能互不相关，进而可刻画不同的生态学现象。本研究利用10个物种多样性（species diversity）、功能多样性（functional diversity）与分类多样性（taxonomic diversity）指数，探究了沿岸大型无脊椎动物（littoral macroinvertebrate）多样性与环境及空间因子的关联。本研究以空间因子作为扩散的替代变量，将多样性指数的变异分解为可归因于环境因子与空间因子的组分。

研究结果表明，相较于局域环境变量，空间过程对多样性指数变异的调控作用总体上相当甚至更强。仅在单一指数（即分类多样性）中，局域环境条件解释了更高比例的变异。上述结果表明，在大型湖泊与海洋沿岸系统等高度连通的水生系统中，高扩散速率带来的质量效应（mass effects）可能会凌驾于局域环境条件（物种分选）对多样性的影响之上。本研究结果还表明，高度连通系统中的生物多样性评估与环境监测，不能仅依赖环境调控这一思路。因此，我们建议在水生系统的基础与应用生态学研究中，应同时整合环境过程与空间过程的作用。