Data from: The role of founder effects on the evolution of reproductive isolation

Several theories argue that large changes in allele frequencies through genetic drift after a small founding population becomes allopatrically isolated can lead to significant changes in reproductive isolation and thus trigger the origin of new species. For this reason, founder speciation has been proposed as a potent force in the generation of new species. Nonetheless, the relative importance of such “founder effects” remains largely untested. In this report, I used experimental evolution to create one thousand replicates that underwent an extreme bottleneck and to study whether founder effects can lead to an increase in reproductive isolation in Drosophila yakuba. Even though the most common outcome of inbreeding is extinction, founder effects can lead to increased premating reproductive isolation in a very small proportion of cases. Changes in reproductive isolation after a founding population bottleneck are similar to changes in other phenotypic traits, in which inbreeding might displace the mean phenotypic value and substantially increase the phenotypic variance. This increase in phenotypic variance does not confer an increase in the response to selection for reproductive isolation in artificial selection experiments, indicating that the increased phenotypic variance is not caused by increases in additive genetic variance. These results also demonstrate that, similar to morphological and life history traits, behavioral traits can be affected by inbreeding and genetic drift.多项理论表明，当小型奠基种群出现异域隔离后，由遗传漂变（genetic drift）介导的等位基因频率（allele frequencies）大幅变化可引发生殖隔离（reproductive isolation）的显著改变，进而触发新物种的起源。基于此，奠基者物种形成（founder speciation）被视作新物种产生的强效驱动力。尽管如此，这类“奠基者效应（founder effects）”的相对重要性仍基本未得到实证检验。 本研究借助实验进化（experimental evolution）技术，构建了一千个经历极端种群瓶颈的重复实验种群，以此探究奠基者效应是否会提升雅库巴果蝇（Drosophila yakuba）的生殖隔离水平。尽管近交（inbreeding）最常见的结局是种群灭绝，但在极少数实验案例中，奠基者效应可提升交配前生殖隔离（premating reproductive isolation）水平。奠基种群经历瓶颈后，生殖隔离的变化模式与其他表型性状（phenotypic traits）的变化类似：近交可偏移表型均值，并显著提升表型方差（phenotypic variance）。该表型方差的提升并未使人工选择实验中生殖隔离的选择响应得到增强，表明该表型方差的增加并非由加性遗传方差（additive genetic variance）提升所导致。 本研究结果同时证实，与形态性状（morphological traits）和生活史性状（life history traits）类似，行为性状（behavioral traits）同样可受到近交与遗传漂变的影响。