Data from: Detecting slow introgression of invasive alleles in an extensively restocked game bird

Interbreeding of two species in the wild implies introgression of alleles from one species into the other only when admixed individuals survive and successfully backcross with the parental species. Consequently, estimating the proportion of first generation hybrids in a population may not inform about the evolutionary impact of hybridization. Samples obtained over a long time span may offer a more accurate view of the spreading of introgressed alleles in a species’ gene pool. Common quail (Coturnix coturnix) populations in Europe have been restocked extensively with farm quails of hybrid origin (crosses with Japanese quails, C. japonica). We genetically monitored a common quail population over 15 years to investigate whether genetic introgression is occurring and used simulations to investigate our power to detect it. Our results revealed that some introgression has occurred, but we did not observe a significant increase over time in the proportion of admixed individuals. However, simulations showed that the degree of admixture may be larger than anticipated due to the limited power of analyses over a short time span, and that observed data was compatible with a low rate of introgression, probably resulting from reduced fitness of admixed individuals. Simulations predicted this could result in extensive admixture in the near future.

野生两物种间的杂交，仅当杂交后代存活并成功与亲本物种回交时，才会发生等位基因从一个物种向另一个物种的渐渗（introgression）。因此，仅通过估算种群内第一代杂交个体的比例，或无法全面揭示杂交事件的进化影响。长期跨度下采集的样本可更精准地展现渐渗等位基因在物种基因库中的扩散态势。欧洲的普通鹌鹑（Coturnix coturnix）种群此前已被大量人工放归源自杂交的养殖鹌鹑——这类养殖鹌鹑为与日本鹌鹑（Coturnix japonica，简称C. japonica）的杂交后代。本研究对某普通鹌鹑种群开展了长达15年的遗传监测，以探究遗传渐渗是否发生，并通过模拟实验评估了本研究对渐渗事件的检测效力。研究结果显示，确实存在一定程度的遗传渐渗，但未观测到杂交个体的比例随时间出现显著上升。然而，模拟实验结果表明：由于短时间跨度下的分析效力有限，实际的种群杂交程度或高于预期；且观测数据与低速率的渐渗事件相契合，这一低速率渐渗大概率源于杂交个体的适合度降低。模拟实验进一步预测，该渐渗模式或在不久的将来引发广泛的种群杂交事件。