Piálek J, Barton N H
Institute of Cell, Animal, and Population Biology, University of Edinburgh, United Kingdom.
Genetics. 1997 Feb;145(2):493-504. doi: 10.1093/genetics/145.2.493.
A local barrier to gene flow will delay the spread of an advantageous allele. Exact calculations for the deterministic case show that an allele that is favorable when rare is delayed very little even by a strong barrier: its spread is slowed by a time proportional to log((B/sigma) square root of 2S)/S, where B is the barrier strength, sigma the dispersal range, and fitnesses are 1:1 + S:1 + 2S. However, when there is selection against heterozygotes, such that the allele cannot increase from low frequency, a barrier can cause a much greater delay. If gene flow is reduced below a critical value, spread is entirely prevented. Stochastic simulations show that with additive selection, random drift slows down the spread of the allele, below the deterministic speed of sigma square root of 2S. The delay to the advance of an advantageous allele caused by a strong barrier can be substantially increased by random drift and increases with B/(2S rho sigma 2) in a one-dimensional habitat of density rho. However, with selection against heterozygotes, drift can facilitate the spread and can free an allele that would otherwise be trapped indefinitely by a strong barrier. We discuss the implications of these results for the evolution of chromosome rearrangements.
基因流动的局部障碍会延缓有利等位基因的传播。确定性情况下的精确计算表明，即使是很强的障碍，对稀有时有利的等位基因的延缓作用也很小：其传播速度减缓的时间与log((B/σ)√(2S))/S成正比，其中B是障碍强度，σ是扩散范围，适合度为1:1 + S:1 + 2S。然而，当存在对杂合子的选择，使得等位基因不能从低频增加时，障碍会导致大得多的延缓。如果基因流动降低到临界值以下，传播就会完全受阻。随机模拟表明，在加性选择下，随机漂变会减缓等位基因的传播速度，低于确定性的σ√(2S)速度。在密度为ρ的一维栖息地中，强障碍对等位基因前进的延缓会因随机漂变而大幅增加，并随B/(2Sρσ²)增加。然而，在对杂合子进行选择时，漂变可以促进传播，并能使一个等位基因从否则会被强障碍无限期困住的状态中解脱出来。我们讨论了这些结果对染色体重排进化的影响。
