UMR 8198 - Evo-Eco-Paleo, CNRS, Univ. Lille, Lille F-59000, France.
Department of Mathematics, University of Vienna, Vienna 1090, Austria.
Genetics. 2024 Nov 6;228(3). doi: 10.1093/genetics/iyae140.
We consider how the genetic architecture underlying locally adaptive traits determines the strength of a barrier to gene flow in a mainland-island model. Assuming a general life cycle, we derive an expression for the effective migration rate when local adaptation is due to genetic variation at many loci under directional selection on the island, allowing for arbitrary fitness and dominance effects across loci. We show how the effective migration rate can be combined with classical single-locus diffusion theory to accurately predict multilocus differentiation between the mainland and island at migration-selection-drift equilibrium and determine the migration rate beyond which local adaptation collapses, while accounting for genetic drift and weak linkage. Using our efficient numerical tools, we then present a detailed study of the effects of dominance on barriers to gene flow, showing that when total selection is sufficiently strong, more recessive local adaptation generates stronger barriers to gene flow. We then study how heterogeneous genetic architectures of local adaptation affect barriers to gene flow, characterizing adaptive differentiation at migration-selection balance for different distributions of fitness effects. We find that a more heterogeneous genetic architecture generally yields a stronger genome-wide barrier to gene flow and that the detailed genetic architecture underlying locally adaptive traits can have an important effect on observable differentiation when divergence is not too large. Lastly, we study the limits of our approach as loci become more tightly linked, showing that our predictions remain accurate over a large biologically relevant domain.
我们探讨了局部适应性特征的遗传结构如何决定大陆-岛屿模型中基因流动障碍的强度。假设一个通用的生命周期，我们推导出了一个表达式，用于描述当岛屿上的定向选择导致许多基因座的遗传变异导致局部适应时的有效迁移率，允许任意的适应度和显性效应跨越基因座。我们展示了如何将有效迁移率与经典的单基因座扩散理论相结合，准确预测大陆和岛屿之间在迁移-选择-漂变平衡下的多基因座分化，并确定局部适应崩溃时的迁移率，同时考虑遗传漂变和弱连锁。然后，我们使用我们的高效数值工具，对主导对基因流动障碍的影响进行了详细的研究，结果表明，当总选择足够强时，更多的隐性局部适应会产生更强的基因流动障碍。然后，我们研究了局部适应性的不同遗传结构如何影响基因流动障碍，为不同适应度效应分布的迁移-选择平衡下的适应性分化进行了特征描述。我们发现，更具异质性的遗传结构通常会产生更强的全基因组基因流动障碍，并且局部适应性特征的详细遗传结构在分歧不是太大时，对可观察到的分化会产生重要影响。最后，我们研究了随着基因座变得更加紧密连锁时我们的方法的限制，结果表明，我们的预测在一个广泛的生物学相关领域仍然是准确的。
