Data from: Biodiversity change is uncoupled from species richness trends: consequences for conservation and monitoring

1. Global concern about human impact on biological diversity has triggered an intense research agenda on drivers and consequences of biodiversity change in parallel with international policy seeking to conserve biodiversity and associated ecosystem functions. Quantifying the trends in biodiversity is far from trivial, however, as recently documented by meta-analyses which report little if any net change of local species richness through time. 2. Here, we summarize several limitations of species richness as a metric of biodiversity change and show that the expectation of directional species richness trends under changing conditions is invalid. Instead, we illustrate how a set of species turnover indices provide more information content regarding temporal trends in biodiversity, as they reflect how dominance and identity shift in communities over time. 3. We apply these metrics to three monitoring data sets representing different ecosystem types. In all data sets, nearly complete species turnover occurred, but this was disconnected from any species richness trends. Instead, turnover was strongly influenced by changes in species presence (identities) and dominance (abundances). We further show that these metrics can detect phases of strong compositional shifts in monitoring data and thus identify a different aspect of biodiversity change decoupled from species richness. 4. Synthesis and application: Temporal trends in species richness are insufficient to capture key changes in biodiversity in changing environments. In fact, reductions in environmental quality can lead to transient increases in species richness if immigration or extinction have different temporal dynamics. Thus, biodiversity monitoring programs need to go beyond analyses of trends in richness in favour of more meaningful assessments of biodiversity change.01-Jun-20171. 人类活动对生物多样性（biological diversity）的影响引发全球广泛关注，催生了围绕生物多样性变化驱动因素与影响的密集研究计划，与此同时国际政策也在致力于保护生物多样性及其关联的生态系统功能（ecosystem functions）。然而，量化生物多样性的变化趋势绝非易事，正如近期荟萃分析（meta-analysis）所记录的那样，这些研究显示本地物种丰富度（species richness）随时间几乎无净变化。 2. 本文总结了将物种丰富度作为生物多样性变化衡量指标的若干局限性，并证明在环境变化条件下预期物种丰富度会呈现单向变化趋势的观点是不成立的。相反，我们阐释了一系列物种周转指数（species turnover indices）如何能提供更多关于生物多样性时间变化趋势的信息——这类指数能够反映群落（communities）内物种优势度与物种身份随时间的变化情况。 3. 我们将这些指标应用于三套代表不同生态系统类型的监测数据集（monitoring data sets）。在所有数据集中，均发生了近乎完全的物种周转，但这一现象与物种丰富度的变化趋势并无关联。相反，物种周转受物种存在（即物种身份）和优势度（即物种多度）的变化强烈影响。我们进一步证明，这些指标能够识别监测数据中群落组成发生显著转变的阶段，从而揭示出与物种丰富度解耦的另一维度的生物多样性变化。 4. 综合与应用：物种丰富度的时间变化趋势不足以捕捉环境变化背景下生物多样性的关键变化。事实上，如果物种迁入或灭绝具有不同的时间动态（temporal dynamics），环境质量下降反而可能导致物种丰富度出现短暂上升。因此，生物多样性监测项目（biodiversity monitoring programs）不应仅局限于物种丰富度的趋势分析，而应转向更具科学意义的生物多样性变化评估方法。2017年6月1日