The effects of linkage and gene flow on local adaptation: a two-locus continent-island model.
The effects of linkage and gene flow on local adaptation: a two-locus continent-island model.
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DOI：
10.1016/j.tpb.2011.07.002
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发表时间：
2011-12
影响因子：
1.4
通讯作者：
Akerman, Ada
中科院分区：
文献类型：
--
作者：
Buerger, Reinhard;Akerman, Ada
关键词：
人口的细分和迁移被认为是连锁不平衡的重要原因。我们通过分析一个在两个连锁基因座上进行基因选择的二倍体确定性大陆-岛屿模型（即，无显性或上位性）。对于这个简单的模型，我们明确地描述了所有可能的平衡配置。在有限的情况下，如弱迁移，弱选择，弱或强重组，获得了许多感兴趣的数量的简单和直观的近似。例如，我们推导出明确的表达式的措施和（平方相关等位基因状态）的LD。它们以不同的方式取决于移民率。在弱连锁基因座之间保持着显著的高值，特别是当基因流较低时。我们确定如何最大量的基因流，承认保存本地适应的单倍型，因此在两个位点的多态性，取决于重组率和选择系数。我们还研究了分化的演变，通过检查与已经存在的，局部适应的等位基因相关的小作用的有益突变体的入侵。影响小得多的突变体可以成功地入侵比天真的单基因座理论所预测的，只要它们至少是弱连锁的。最后，探讨了连锁对中性位点的局部适应程度、迁移负荷和有效迁移率的影响。我们讨论了遗传结构进化的可能后果，特别是紧密相连的，稍微有益的突变和重组和染色体倒位的进化簇的出现。
Population subdivision and migration are generally considered to be important causes of linkage disequilibrium (LD). We explore the combined effects of recombination and gene flow on the amount of LD, the maintenance of polymorphism, and the degree of local adaptation in a subdivided population by analyzing a diploid, deterministic continent–island model with genic selection on two linked loci (i.e., no dominance or epistasis). For this simple model, we characterize explicitly all possible equilibrium configurations. Simple and intuitive approximations for many quantities of interest are obtained in limiting cases, such as weak migration, weak selection, weak or strong recombination. For instance, we derive explicit expressions for the measures and (the squared correlation in allelic state) of LD. They depend in qualitatively different ways on the migration rate. Remarkably high values of are maintained between weakly linked loci, especially if gene flow is low. We determine how the maximum amount of gene flow that admits preservation of the locally adapted haplotype, hence of polymorphism at both loci, depends on recombination rate and selection coefficients. We also investigate the evolution of differentiation by examining the invasion of beneficial mutants of small effect that are linked to an already present, locally adapted allele. Mutants of much smaller effect can invade successfully than predicted by naive single-locus theory provided they are at least weakly linked. Finally, the influence of linkage on the degree of local adaptation, the migration load, and the effective migration rate at a neutral locus is explored. We discuss possible consequences for the evolution of genetic architecture, in particular, for the emergence of clusters of tightly linked, slightly beneficial mutations and the evolution of recombination and chromosome inversions.
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