Allelic diversity for neutral markers retains a higher adaptive potential for quantitative traits than expected heterozygosity

The adaptive potential of a population depends on the amount of additive genetic variance for quantitative traits of evolutionary importance. This variance is a direct function of the expected frequency of heterozygotes for the loci which affect the trait (QTL). It has been argued, but not demonstrated experimentally, that long-term response to selection is more dependent on QTL allelic diversity than on QTL heterozygosity. Conservation programmes, aimed at preserving this variation, usually rely on neutral markers rather than on quantitative traits for making decisions on management. Here, we address, both through simulation analyses and experimental studies with Drosophila melanogaster, the question of whether allelic diversity for neutral markers is a better indicator of a high adaptive potential than expected heterozygosity. In both experimental and simulation studies, we established synthetic populations for which either heterozygosity or allelic diversity was maximized using information from QTL (simulations) or unlinked neutral markers (simulations and experiment). The synthetic populations were selected for the quantitative trait to evaluate the evolutionary potential provided by the two optimization methods. Our results show that maximizing the number of alleles of a low number of markers implies higher responses to selection than maximizing their heterozygosity.

种群的适应潜力，取决于与进化相关的数量性状的加性遗传方差总量。该方差直接由影响该性状的数量性状基因座（quantitative trait locus, QTL）的杂合子预期频率所决定。已有观点提出，但尚未经实验证实：长期选择响应更依赖于QTL等位基因多样性，而非QTL杂合度。旨在保留此类遗传变异的保育计划，在制定管理决策时通常优先选用中性标记而非数量性状。本研究通过模拟分析与黑腹果蝇（Drosophila melanogaster）实验研究，探讨了中性标记的等位基因多样性是否较预期杂合度更能有效指示种群的高适应潜力。在实验与模拟研究中，我们分别基于QTL信息（仅模拟研究）或非连锁中性标记（模拟与实验研究）构建了两类合成种群：一类以最大化杂合度为目标，另一类以最大化等位基因多样性为目标。针对该数量性状对上述合成种群开展选择实验，以评估这两种优化策略所赋予的进化潜力。研究结果表明，相较于最大化标记的杂合度，通过少量标记实现等位基因数量最大化，可带来更高的选择响应。