Data from: Model adequacy and microevolutionary explanations for stasis in the fossil record

Long-term phenotypic stasis is frequently observed in the fossil record, but not readily predicted from microevolutionary theory. To test competing explanations for stasis on macroevolutionary time scales we need reliably estimated parameters from appropriate evolutionary models that adequately describe the evolutionary trait dynamics. Here, we develop tests to assess the adequacy of the most commonly used stasis model in evolutionary biology and apply them to time series of phenotypic traits from fossil lineages. Of the 572 fossil time series we analyzed from the literature, 263 times series showed a better fit to the stasis model relative to alternative models, but only 172 of those fitted the stasis model both in relative and absolute terms. The estimated trait variances from these 172 time series do not correlate with rough proxies of effective population size. Our preliminary investigation of the fixed-optimum hypothesis hence fails to give empirical support to the idea that genetic drift around a constant trait optimum is an explanation for stasis in the fossil record. We argue that optima following stationary processes on the adaptive landscape is a viable hypothesis for stasis that needs further investigation. We end by discussing how investigations of model adequacy can be a valuable approach for increasing our understanding of the dynamics of the adaptive landscape on macroevolutionary time scales.

化石记录中频繁观测到长期表型停滞（phenotypic stasis）现象，但微进化理论（microevolutionary theory）却难以对其作出预测。为在宏观进化时间尺度（macroevolutionary time scales）上检验针对停滞现象的多种竞争性解释，我们需要从能够充分描述进化性状动态（evolutionary trait dynamics）的恰当进化模型（evolutionary model）中获取可靠估计的参数。本研究开发了用于评估进化生物学中最常用停滞模型（stasis model）适配性的检验方法，并将其应用于来自化石谱系（fossil lineage）的表型性状时间序列。在我们从已有文献中分析的572条化石时间序列中，有263条序列相较于其他备选模型，与停滞模型的拟合效果更优，但其中仅有172条序列在相对和绝对层面均符合停滞模型的假设。这172条序列所估计出的性状方差，与有效种群大小（effective population size）的粗略代理变量之间并无相关性。因此，我们针对固定最适假说（fixed-optimum hypothesis）的初步研究，未能为“围绕恒定性状最适值的遗传漂变（genetic drift）可解释化石记录中的停滞现象”这一观点提供实证支持。我们认为，适应性景观（adaptive landscape）上的最适值遵循平稳过程这一假说，是解释停滞现象的可行方向，有待进一步研究。最后，我们讨论了模型适配性研究如何能成为提升我们对宏观进化时间尺度下适应性景观动态认知的有效途径。