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Abstract：
There are two primary measures of the amount of genetic variation in a population at a locus: heterozygosity and the number of alleles. Effective population size (N e) provides both an expectation of the amount of heterozygosity in a population at drift-mutation equilibrium and the rate of loss of heterozygosity because of genetic drift. In contrast, the number of alleles in a population at drift-mutation equilibrium is a function of both N e and census size (N C). In addition, populations with the same N e can lose allelic variation at very different rates. Allelic variation is generally much more sensitive to bottlenecks than heterozygosity. Expressions used to adjust for the effects of violations of the ideal population on N e do not provide good predictions of the loss of allelic variation. These effects are much greater for loci with many alleles, which are often important for adaptation. We show that there is a linear relationship between the reduction of N C and the corresponding reduction of the expected number of alleles at drift-mutation equilibrium. This makes it possible to predict the expected effect of a bottleneck on allelic variation. Heterozygosity provides good estimates of the rate of adaptive change in the short-term, but allelic variation provides important information about long-term adaptive change. The guideline of long-term N e being greater than 500 is often used as a primary genetic metric for evaluating conservation status. We recommend that this guideline be expanded to take into account allelic variation as well as heterozygosity.
摘要：
在一个基因座处的群体中遗传变异量有两个主要量度:杂合性和等位基因数量。有效种群大小（Ne）既提供了在漂移-突变平衡下种群中杂合性的期望值，也提供了由于遗传漂移而导致的杂合性丢失率。相比之下,处于漂移突变平衡状态的种群中的等位基因数量是Ne和人口普查大小（NC）的函数。此外,具有相同Ne的种群可以以非常不同的速率失去等位基因变异。等位基因变异通常比杂合性对瓶颈更敏感。用于调整违反理想种群对Ne的影响的表达不能很好地预测等位基因变异的损失。对于具有许多等位基因的基因座，这些影响要大得多，这通常对适应很重要。我们表明，在漂移-突变平衡时，NC的减少与预期等位基因数的相应减少之间存在线性关系。这使得可以预测瓶颈对等位基因变异的预期影响。杂合性提供了短期适应性变化率的良好估计，但等位基因变异提供了有关长期适应性变化的重要信息.长期Ne大于500的准则通常用作评估保护状态的主要遗传指标。我们建议扩展该指南，以考虑等位基因变异和杂合性。
