Simple versus complex models of trait evolution and stasis as a response to environmental change

Previous analyses of evolutionary patterns, or modes, in fossil lineages have focused overwhelmingly on three simple models: stasis, random walks, and directional evolution. Here we use likelihood methods to fit an expanded set of evolutionary models to a large compilation of ancestor–descendant series of populations from the fossil record. In addition to the standard three models, we assess more complex models with punctuations and shifts from one evolutionary mode to another. As in previous studies, we find that stasis is common in the fossil record, as is a strict version of stasis that entails no real evolutionary changes. Incidence of directional evolution is relatively low (13%), but higher than in previous studies because our analytical approach can more sensitively detect noisy trends. Complex evolutionary models are often favored, overwhelmingly so for sequences comprising many samples. This finding is consistent with evolutionary dynamics that are, in reality, more complex tha...过往针对化石支系进化模式的分析，绝大多数都聚焦于三类简单模型：进化停滞（stasis）、随机游走（random walks）与定向进化（directional evolution）。本研究采用似然法（likelihood methods），将一组扩展后的进化模型拟合至由化石记录汇编得到的大型祖先-后裔种群序列数据集。除上述三类经典模型外，我们还评估了包含进化间断以及不同进化模式间切换的更为复杂的进化模型。与既往研究结果一致，我们发现进化停滞在化石记录中十分常见，其中还包括一类不发生任何实质性进化改变的严格停滞模式。定向进化的发生率相对较低（13%），但较以往研究更高，这是因为本研究的分析方法能够更灵敏地检测出带有噪声的进化趋势。复杂进化模型往往更受支持，在样本量较多的序列中这一优势尤为显著。该发现与现实中更为复杂的进化动力学相符……