MAINTENANCE OF POLYGENIC VARIATION IN SPATIALLY STRUCTURED POPULATIONS - ROLES FOR LOCAL MATING AND GENETIC REDUNDANCY
MAINTENANCE OF POLYGENIC VARIATION IN SPATIALLY STRUCTURED POPULATIONS - ROLES FOR LOCAL MATING AND GENETIC REDUNDANCY
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DOI：
10.2307/2409861
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发表时间：
1992-04-01
期刊：
影响因子：
3.3
通讯作者：
HOLSINGER, KE
中科院分区：
文献类型：
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作者：
GOLDSTEIN, DB;HOLSINGER, KE
尽管可遗传的基因变异对进化过程至关重要，但我们对它是如何维持的知之甚少。显然，突变选择平衡必须发挥作用，但它是否能解释在自然种群中普遍存在的高达0.5的遗传率，这一点存在相当大的疑问。大多数突变-选择平衡模型都假设种群是泛型的。在本文中，我们使用蒙特卡罗模拟来检验距离隔离对多基因性状中由突变维持的变异的影响。我们表明，距离隔离可以大大增加在大范围分散模式下连续种群中保持的总变异，但前提是多个基因型产生最佳表型（遗传冗余）。距离隔离对中性等位基因在总体中保持的变异只有轻微的影响。然而，距离隔离和遗传冗余的综合效应使得尽管有很强的稳定选择，但仍能保持大量的变异。机制很简单。距离隔离使得突变和漂移在种群的不同部分独立发生。由于其独立的进化历史，种群的不同部分独立地从可用的冗余基因型集中提取。由于基因型是冗余的，自然选择不会对它们进行区分，它们将一直存在，直到被漂变所消除。人口作为一个整体保持许多不同的基因型。我们发现，这一过程允许突变保持高水平的变异，即使在强大的稳定选择下，并且在中等范围的分散模式中，整个种群中保持的变异量与选择的强度和分散距离的方差无关。此外，我们表明，当选择强时，个体杂合性在局部交配群体中增加。最后，我们的模拟提供了选择和扩散模式如何影响遗传和表型变异的空间分布的粗略图景。
Although heritable genetic variation is critical to the evolutionary process, we know little about how it is maintained. Obviously, mutation-selection balance must play a role, but there is considerable doubt over whether it can account for heritabilities as high as 0.5, which are commonly found in natural populations. Most models of mutation-selection balance assume panmictic populations. In this paper we use Monte Carlo simulations to examine the effect of isolation by distance on the variation maintained by mutation in a polygenic trait subject to optimizing selection. We show that isolation by distance can substantially increase the total variation maintained in continuous populations over a wide range of dispersal patterns, but only if more than one genotype produces the optimal phenotype (genetic redundancy). Isolation by distance alone has only a slight effect on the variation maintained in the total population for neutral alleles. The combined effect of isolation by distance and genetic redundancy, however, allows the maintenance of substantial variation despite strong stabilizing selection. The mechanism is straightforward. Isolation by distance allows mutation and drift to operate independently in different parts of the population. Because of their independent evolutionary histories, different parts of the population independently draw from the available set of redundant genotypes. Because the genotypes are redundant, selection does not discriminate among them, and they will persist until eliminated by drift. The population as a whole maintains many distinct genotypes. We show that this process allows mutation to maintain high levels of variation, even under strong stabilizing selection, and that over a moderate range of dispersal patterns the amount of variation maintained in the entire population is independent of both the strength of selection and the variance of the dispersal distance. Furthermore, we show that individual heterozygosity is increased in locally mating populations when selection is strong. Finally, our simulations provide a rough picture of how selection and the dispersal pattern influence the spatial distribution of genetic and phenotypic variation.