Voje Kjetil Lysne, Saito-Kato Megumi, Spanbauer Trisha L
Natural History Museum, P.O. 1172, Blindern, Oslo 0318, Norway.
Department of Geology and Paleontology, National Museum of Nature and Science, Tsukuba, Japan.
J Evol Biol. 2024 Dec 2;37(12):1551-1562. doi: 10.1093/jeb/voae087.
Extrapolating microevolutionary models does not always provide satisfactory explanations for phenotypic diversification on million-year time scales. For example, short-term evolutionary change is often modelled assuming a fixed adaptive landscape, but macroevolutionary changes are likely to involve changes in the adaptive landscape itself. A better understanding of how the adaptive landscape changes across different time intervals and how these changes cause populations to evolve has the potential to narrow the gap between micro- and macroevolution. Here, we analyze two fossil diatom time series of exceptional quality and resolution covering time intervals of a few hundred thousand years using models that account for different behaviours of the adaptive landscape. We find that one of the lineages evolves on a randomly and continuously changing landscape, whereas the other lineage evolves on a landscape that shows a rapid shift in the position of the adaptive peak of a magnitude that is typically associated with species-level differentiation. This suggests phenotypic evolution beyond generational timescales may be a consequence of both gradual and sudden repositioning of adaptive peaks. Both lineages show rapid and erratic evolutionary change and are constantly readapting towards the optimal trait state, observations that align with evolutionary dynamics commonly observed in contemporary populations. The inferred trait evolution over a span of a few hundred thousand years in these two lineages is, therefore, chimeric in the sense that it combines components of trait evolution typically observed on both short and long timescales.
推断微观进化模型并不总是能为百万年时间尺度上的表型多样化提供令人满意的解释。例如，短期进化变化通常在假设固定适应景观的情况下建模，但宏观进化变化可能涉及适应景观本身的变化。更好地理解适应景观如何在不同时间间隔内变化以及这些变化如何导致种群进化，有可能缩小微观和宏观进化之间的差距。在这里，我们使用考虑了适应景观不同行为的模型，分析了两个质量和分辨率极高的硅藻化石时间序列，这些序列涵盖了几十万年的时间间隔。我们发现，其中一个谱系在随机且不断变化的景观上进化，而另一个谱系在一个景观上进化，该景观显示出适应峰位置的快速移动，其幅度通常与物种水平的分化相关。这表明超越代际时间尺度的表型进化可能是适应峰逐渐和突然重新定位的结果。两个谱系都显示出快速且不稳定的进化变化，并不断重新适应最优性状状态，这些观察结果与当代种群中常见的进化动态一致。因此，在这两个谱系中推断出的几十万年时间跨度内的性状进化是嵌合的，因为它结合了通常在短期和长期时间尺度上观察到的性状进化成分。
