Data from: Habitat connectivity and in-stream vegetation control temporal variability of benthic invertebrate communities

One of the key challenges to understanding patterns of β diversity is to disentangle deterministic patterns from stochastic ones. Stochastic processes may mask the influence of deterministic factors on community dynamics, hindering identification of the mechanisms causing variation in community composition. We studied temporal β diversity (among-year dissimilarity) of macroinvertebrate communities in near-pristine boreal streams across 14 years. To assess whether the observed β diversity deviates from that expected by chance, and to identify processes (deterministic vs. stochastic) through which different explanatory factors affect community variability, we used a null model approach. We observed that at the majority of sites temporal β diversity was low indicating high community stability. When stochastic variation was unaccounted for, connectivity was the only variable explaining temporal β diversity, with weakly connected sites exhibiting higher community variability through time. After accounting for stochastic effects, connectivity lost importance, suggesting that it was related to temporal β diversity via random colonization processes. Instead, β diversity was best explained by in-stream vegetation, community variability decreasing with increasing bryophyte cover. These results highlight the potential of stochastic factors to dampen the influence of deterministic processes, affecting our ability to understand and predict changes in biological communities through time.

解析确定性模式与随机模式的差异，是阐释β多样性(β diversity)分布格局的核心挑战之一。随机过程可能掩盖确定性因素对群落动态的影响，进而阻碍对驱动群落组成变异的机制的识别。我们对14年间近乎原始的北方溪流中的大型无脊椎动物（macroinvertebrate）群落展开研究，分析了其时间尺度下的β多样性——即年间相异度（among-year dissimilarity）。为验证观测得到的β多样性是否偏离随机预期，并识别不同解释因子通过确定性或随机过程影响群落变异性的具体路径，我们采用了零模型（null model）分析方法。研究结果显示，绝大多数样点的时间β多样性水平较低，表明群落稳定性较高。在未纳入随机变异的分析中，连通性是唯一能够解释时间β多样性的变量：连通性较弱的样点，其群落随时间推移的变异性更高。当纳入随机效应后，连通性的解释能力显著下降，这提示其与时间β多样性的关联实际源于随机定殖过程。取而代之的是，河道内植被状况能够最佳解释β多样性的变异：群落变异性随苔藓植物（bryophyte）覆盖度的提升而降低。本研究结果凸显了随机因素可抑制确定性过程的影响，进而削弱我们理解与预测生物群落随时间变化的能力。