Data from: Diversity-dependent evolutionary rates in early Paleozoic zooplankton

The extent to which biological diversity affects rates of diversification is central to understanding macroevolutionary dynamics, yet no consensus has emerged on the importance of diversity-dependence of evolutionary rates. Here we analyse the species-level fossil record of early Paleozoic graptoloids, documented with high temporal resolution, to test directly whether rates of diversification were influenced by levels of standing diversity within this major clade of marine zooplankton. To circumvent the statistical regression-to-the-mean artefact, whereby higher- and lower-than-average values of diversity tend to be followed by negative and positive diversification rates, we construct a non-parametric, empirically scaled, diversity-independent null model by randomizing the observed diversification rates with respect to time. Comparing observed correlations between diversity and diversification rate to those expected from this diversity-independent model, we find evidence for negative diversity-dependence, accounting for up to 12% of the variance in diversification rate, with maximal correlation at a temporal lag of ~1 million years. Diversity-dependence persists throughout the Ordovician and Silurian, despite a major increase in the strength and frequency of extinction and speciation pulses in the Silurian. In contrast to some previous work, we find that diversity-dependence affects rates of speciation and extinction nearly equally on average, although subtle differences emerge when we compare the Ordovician and Silurian.生物多样性对分化速率的影响程度，是理解宏观演化动力学的核心议题，但学界至今尚未就演化速率的多样性依赖效应的重要性达成共识。本研究针对早古生代笔石类（graptoloids）的物种级化石记录展开分析，该记录拥有极高的时间分辨率，旨在直接检验这一海洋浮游动物大型演化支内的分化速率是否受到存续多样性水平的影响。为规避统计上的均值回归伪影——即多样性高于或低于平均值的情况，后续往往分别对应负向与正向的分化速率——我们通过对观测到的分化速率按时间进行随机化处理，构建了一个非参数、经验标定且独立于多样性的零模型。将多样性与分化速率之间的观测相关性，与该独立多样性模型所预测的相关性进行对比后，我们发现了负向多样性依赖效应的证据：该效应可解释分化速率高达12%的方差，且在约1百万年的时间滞后下相关性达到峰值。尽管志留纪期间灭绝与物种形成脉冲的强度与频率大幅提升，但多样性依赖效应在整个奥陶纪与志留纪均持续存在。与部分此前的研究结论不同，我们发现平均而言，多样性依赖效应对物种形成速率与灭绝速率的影响近乎相当，但在对比奥陶纪与志留纪时会出现细微差异。