Plankton Ecology Lab, Institute for Chemistry and Biology of the Marine Environment, Carl von Ossietzky University Oldenburg, Wilhelmshaven, Germany.
Institute of Aquatic Ecology, University of Girona, Girona, Spain.
Nat Ecol Evol. 2023 Jul;7(7):994-1001. doi: 10.1038/s41559-023-02078-w. Epub 2023 Jun 5.
The discrepancy between global loss and local constant species richness has led to debates over data quality, systematic biases in monitoring programmes and the adequacy of species richness to capture changes in biodiversity. We show that, more fundamentally, null expectations of stable richness can be wrong, despite independent yet equal colonization and extinction. We analysed fish and bird time series and found an overall richness increase. This increase reflects a systematic bias towards an earlier detection of colonizations than extinctions. To understand how much this bias influences richness trends, we simulated time series using a neutral model controlling for equilibrium richness and temporal autocorrelation (that is, no trend expected). These simulated time series showed significant changes in richness, highlighting the effect of temporal autocorrelation on the expected baseline for species richness changes. The finite nature of time series, the long persistence of declining populations and the potential strong dispersal limitation probably lead to richness changes when changing conditions promote compositional turnover. Temporal analyses of richness should incorporate this bias by considering appropriate neutral baselines for richness changes. Absence of richness trends over time, as previously reported, can actually reflect a negative deviation from the positive biodiversity trend expected by default.
全球物种损失与局部物种丰富度不变之间的差异，引发了关于数据质量、监测计划系统偏差以及物种丰富度是否足以捕捉生物多样性变化的争论。我们表明，尽管独立且平等的定居和灭绝过程中存在系统偏差，但稳定丰富度的零预期可能是错误的。我们分析了鱼类和鸟类的时间序列，发现整体丰富度有所增加。这种增加反映了一种系统偏差，即更早地检测到定居而不是灭绝。为了了解这种偏差对丰富度趋势的影响程度，我们使用中性模型模拟了时间序列，该模型控制了平衡丰富度和时间自相关（即，预计没有趋势）。这些模拟时间序列显示出丰富度的显著变化，突出了时间自相关对物种丰富度变化预期基线的影响。时间序列的有限性、下降种群的长期持续存在以及潜在的强扩散限制，可能会导致在变化的条件促进组成性转变时发生丰富度变化。丰富度的时间分析应通过考虑适当的中性丰富度变化基线来纳入这种偏差。正如之前报道的那样，随着时间的推移缺乏丰富度趋势，实际上可能反映了默认情况下预期的积极生物多样性趋势的负偏差。
