Abstract：
The rate at which beneficial alleles fix in a population depends on the probability of and time to fixation of such alleles. Both of these quantities can be significantly impacted by population subdivision and limited gene flow. Here, we investigate how limited dispersal influences the rate of fixation of beneficial de novo mutations, as well as fixation time from standing genetic variation. We investigate this for a population structured according to the island model of dispersal allowing us to use the diffusion approximation, which we complement with simulations. We find that fixation may take on average fewer generations under limited dispersal than under panmixia when selection is moderate. This is especially the case if adaptation occurs from de novo recessive mutations, and dispersal is not too limited (such that approximately FST<0.2). The reason is that mildly limited dispersal leads to only a moderate increase in effective population size (which slows down fixation), but is sufficient to cause a relative excess of homozygosity due to inbreeding, thereby exposing rare recessive alleles to selection (which accelerates fixation). We also explore the effect of metapopulation dynamics through local extinction followed by recolonization, finding that such dynamics always accelerate fixation from standing genetic variation, while de novo mutations show faster fixation interspersed with longer waiting times. Finally, we discuss the implications of our results for the detection of sweeps, suggesting that limited dispersal mitigates the expected differences between the genetic signatures of sweeps involving recessive and dominant alleles.
摘要：
群体中有益等位基因固定的速率取决于固定此类等位基因的概率和时间。这两个数量都可能受到人口细分和有限基因流的显着影响。这里,我们研究了有限的分散如何影响有益的从头突变的固定率，以及站立遗传变异的固定时间。我们针对根据扩散岛模型构造的种群进行研究，允许我们使用扩散近似，我们用模拟来补充。我们发现，在选择适度的情况下，在有限的分散下，固定的时间平均比在panmixia下少。如果适应发生于从头隐性突变，情况尤其如此，和分散没有太受限制(使得大约FST<0.2)。原因是轻度有限的分散只会导致有效种群规模的适度增加（这会减慢固定速度），但由于近亲繁殖而足以导致纯合性相对过量，从而将罕见的隐性等位基因暴露于选择（加速固定）。我们还探索了通过局部灭绝然后重新定居的种群动态的影响，发现这种动态总是加速固定的遗传变异，而从头突变显示出更快的固定，并伴随着更长的等待时间。最后,我们讨论了我们的结果对扫描检测的影响，这表明有限的分散减轻了涉及隐性和显性等位基因的扫描的遗传特征之间的预期差异。
