周期性迁移对亚分群中选择的影响

中文摘要 AI 辅助

迁移和选择共同塑造了空间结构种群中的进化结果。迁移可能随时间变化，如海平面变化等生态转变会改变栖息地连通性。在此，我们研究了周期性迁移对地理上亚分群中自然选择的影响。利用具有空间异质性选择的双位点Moran模型，我们分析了一种突变基因型在一个栖息地有利而在另一个栖息地不利的场景。在保持时间平均迁移率固定的情况下，我们改变迁移的周期、相对相位和方向不对称性，并检查由此产生的稳态突变频率。我们发现，迁移周期性通常驱动种群趋向中性：相对于恒定迁移，当突变体平均有利时，它降低突变频率；当突变体平均有害时，它增加突变频率，但在所检查的参数范围内不会逆转选择方向。这种效应对于异相迁移（模拟季节性迁移）最强，并因方向不对称性而进一步增强。对迁移周期的响应通常是非单调的，在同步迁移下，一个中间特征周期产生与恒定迁移行为最大的偏差。这些结果源于Moran过程中迁移与局部选择的耦合：迁移的时间调节不仅改变个体在栖息地之间的交换，还改变选择所作用的局部种群组成。我们的结果表明，具有相同平均迁移率的种群可以根据基因流的时间组织表现出不同的进化结果。

英文摘要

Migration and selection jointly shape evolutionary outcomes in spatially structured populations. Migration can vary over time as ecological shifts, such as changes in sea level, alter habitat connectivity. Here, we study the impact of periodic migration on selection within a geographically subdivided population. Using a two-deme Moran model with spatially heterogeneous selection, we analyze a scenario in which a mutant genotype is advantageous in one habitat and disadvantageous in the other. Keeping the time-averaged migration rate fixed, we vary the period, relative phase, and directional asymmetry of migration and examine the resulting steady-state mutant frequency. We find that migration periodicity generally drives the population toward neutrality: relative to constant migration, it decreases the mutant frequency when mutants are advantageous on average and increases it when they are deleterious, without reversing the direction of selection in the parameter regimes examined. This effect is strongest for out-of-phase migration, which models seasonal migration, and is further enhanced by directional asymmetry. The response to the migration period is generally non-monotonic, with an intermediate characteristic period producing the largest deviation from constant-migration behavior under in-phase migration. These results arise from the coupling between migration and local selection in Moran process: temporal modulation of migration changes not only the exchange of individuals between habitats but also the local population composition on which selection acts. Our results show that populations with identical mean migration rates can show different evolutionary outcomes depending on the temporal organization of gene flow.

发表机构

• Sharif University of Technology（谢里夫理工大学）
• University of Minnesota（明尼苏达大学）
• ICTP – The Abdus Salam International Centre for Theoretical Physics（国际理论物理中心（阿卜杜斯·萨拉姆国际理论物理中心））

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