Data from: Cenozoic latitudinal response curves: individualistic changes in the latitudinal distributions of marine bivalves and gastropods

We use a Gaussian logistic regression model to characterize epoch-to-epoch and stage-tostage changes in the latitudinal response curves of Cenozoic marine bivalve and gastropod genera along the global latitudinal gradient, and analyze these changes to understand the mode and tempo of changes in latitudinal distribution. A ubiquitous ‘‘hollow curve’’ pattern is apparent, wherein smaller changes in response-curve parameters are much more common than larger changes. Curves are strikingly consistent in terms of the average level of change exhibited, despite the many unique environmental and biological changes documented between each of these intervals. This implies that the pace and magnitude of changes in the latitudinal distribution of marine mollusks are not controlled, in aggregate, by time-period-specific conditions. Additionally, we find no evidence for long-term migration from tropical to extratropical latitudes. Our results instead favor a model of either equatorward migration or no general trend. This likely reflects the tendency of genera to maintain their highest concentrations in the tropics even if their ranges become extended out of the tropics over time.

我们采用高斯逻辑回归模型（Gaussian logistic regression model），刻画沿全球纬度梯度的新生代（Cenozoic）海洋双壳类（bivalve）与腹足类（gastropod）属的纬度响应曲线（latitudinal response curve）在不同地质世（epoch）与阶（stage）间的演化变化，并通过分析此类变化以探究纬度分布变化的模式与速率。研究发现一种普遍存在的“中空曲线”模式：响应曲线参数的小幅变化远多于大幅变化。尽管各研究时段间隔内均记录到诸多独特的环境与生物扰动事件，但这些曲线在平均变化水平上表现出惊人的一致性。这表明，总体而言海洋软体动物（marine mollusk）纬度分布变化的速率与幅度，并不受特定时期专属环境条件的调控。此外，我们未发现存在从热带向温带纬度长期迁移的证据。我们的研究结果反而支持两类模型中的一种：要么发生向赤道的迁移，要么不存在整体迁移趋势。这一现象大概率反映了各属的固有倾向：即便其分布范围随时间拓展至热带以外区域，仍会在热带地区维持最高的种群富集度。