美国斯坦福大学D. A. Petrov、M. C. Bitter和 宾夕法尼亚大学P. Schmidt研究团队提出，不断波动的选择揭示了适应的细粒度。该项研究成果发表在2024年8月14日出版的《自然》上。

研究人员从6月下旬至12月中旬，在广泛复制的田间生态系统中，每1-2代对遗传多样化的黑腹果蝇(Drosophila melanogaster)群体进行全基因组等位基因频率数据采集(共12代)。种群扩张、峰值密度和崩溃等基本生态阶段的适应是由重复中基因组变异极其快速、平行的变化所支撑的。

然而，选择的主导方向反复波动，甚至在每一个生态阶段中也是如此。将等位基因频率的变化模式与从同一实验系统获得的独立数据集进行比较，表明选择的目标是可预测的。

一致地，他们的结果揭示了常备变异的适应性相关性，而这种变异可能会被基于静态总体抽样或未充分解析的时间序列数据的推理方法所掩盖。研究组认为，这种精细的、暂时波动的选择可能是维持自然种群中功能性遗传变异的重要力量，也是影响关联中性位点全基因组多样性模式的重要随机力量，类似于遗传漂变。

据了解，时间波动的环境条件是自然栖息地普遍存在的特征。然而，自然种群如何通过遗传变异的变化来适应波动的选择压力是未知的。

附：英文原文

Title: Continuously fluctuating selection reveals fine granularity of adaptation

Author: Bitter, M. C., Berardi, S., Oken, H., Huynh, A., Lappo, Egor, Schmidt, P., Petrov, D. A.

Issue&Volume: 2024-08-14

Abstract: Temporally fluctuating environmental conditions are a ubiquitous feature of natural habitats. Yet, how finely natural populations adaptively track fluctuating selection pressures via shifts in standing genetic variation is unknown1,2. Here we generated genome-wide allele frequency data every 1–2 generations from a genetically diverse population of Drosophila melanogaster in extensively replicated field mesocosms from late June to mid-December (a period of approximately 12 total generations). Adaptation throughout the fundamental ecological phases of population expansion, peak density and collapse was underpinned by extremely rapid, parallel changes in genomic variation across replicates. Yet, the dominant direction of selection fluctuated repeatedly, even within each of these ecological phases. Comparing patterns of change in allele frequency to an independent dataset procured from the same experimental system demonstrated that the targets of selection are predictable across years. In concert, our results reveal a fitness relevance of standing variation that is likely to be masked by inference approaches based on static population sampling or insufficiently resolved time-series data. We propose that such fine-scaled, temporally fluctuating selection may be an important force contributing to the maintenance of functional genetic variation in natural populations and an important stochastic force impacting genome-wide patterns of diversity at linked neutral sites, akin to genetic draft.

DOI: 10.1038/s41586-024-07834-x

Source: https://www.nature.com/articles/s41586-024-07834-x