Data from: Tempo does not correlate with mode in the fossil record

The dominating view of evolution based on the fossil record is that established species remain more or less unaltered during their existence. Substantial evolution is on the other hand routinely reported for contemporary populations, and most quantitative traits show high potential for evolution. These contrasting observations on long and short time scales are often referred to as the paradox of stasis, which rests on the fundamental assumption that periods of morphological stasis in the fossil record represent minimal evolutionary change. Investigating 450 fossil time series, I demonstrate that the non-accumulating morphological fluctuations during stasis travel similar distances in morphospace space compared to lineages showing directional change. Hence, lineages showing stasis are commonly undergoing considerable amounts of evolution, but this evolution does not accumulate to produce large net evolutionary changes over time. Rates of evolutionary change across modes in the fossil record may be more homogenous than previously assumed and advocated, supporting the claim that substantial evolution is not exclusively or causally linked to the process of speciation. Instead of exemplifying minimal evolution, stasis likely represents information on the dynamics of the adaptive landscape on macroevolutionary time scales, including the persistence of adaptive zones and ecological niches over millions of years.

基于化石记录的演化学主流观点认为，已确立的物种在其存续期间基本保持不变。另一方面，当代种群中却常被报道存在显著演化，且大多数数量性状均具备较高的演化潜力。这种长、短时间尺度下的观测结果相悖的情况，通常被称为停滞悖论（paradox of stasis），其核心前提假设为：化石记录中出现的形态停滞阶段代表着极小的演化变化量。本研究通过分析450条化石时间序列，证明：停滞阶段中未发生累积的形态波动，其在形态空间（morphospace）中移动的距离，与表现出定向演化的支系相当。因此，表现出停滞的支系通常正经历着显著的演化过程，但这类演化并未发生累积，无法在较长时间内产生较大的净演化变化量。化石记录中不同演化模式下的演化速率，或许比此前假设和主张的更为均一，这支撑了“显著演化并非仅与物种形成过程存在排他性或因果关联”这一论断。停滞现象并非代表极小程度的演化，反而可能反映了宏演化（macroevolution）时间尺度下的适应性景观动态信息，其中包括适应性地带（adaptive zone）与生态位（ecological niche）在数百万年间的存续情况。