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.

多项理论提出，当小型奠基种群（founding population）发生异域隔离（allopatrically isolated）后，通过遗传漂变（genetic drift）引发的等位基因频率（allele frequencies）大幅波动，可导致生殖隔离（reproductive isolation）出现显著改变，进而触发新物种的起源。正因如此，奠基者成种（founder speciation）被视作催生新物种的强劲演化动力。尽管如此，这类“奠基者效应（founder effects）”的相对重要性，在很大程度上仍未得到实证检验。本研究借助实验进化（experimental evolution）技术，构建了1000个经历极端瓶颈效应（extreme bottleneck）的重复种群，以此探究奠基者效应是否能在雅库巴果蝇（Drosophila yakuba）中引发生殖隔离水平的提升。尽管近交（inbreeding）最常见的结局是种群灭绝，但在极少数案例中，奠基者效应可提升交配前生殖隔离（premating reproductive isolation）的水平。奠基种群经历瓶颈效应后，生殖隔离的变化模式与其他表型性状（phenotypic traits）的变化类似：近交可能改变表型均值，并大幅提升表型方差。在人工选择实验中，表型方差的提升并未带来生殖隔离相关选择响应的增强，这表明表型方差的增加并非由加性遗传方差（additive genetic variance）升高所导致。本研究结果还证实，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。