Data from: Rapid polygenic response to secondary contact in a hybrid species

Secondary contact between closely related species can have genetic consequences. Competition for essential resources may lead to divergence in heritable traits that reduces interspecific competition, thus leading to increased genetic divergence. Conversely, hybridization and backcrossing can lead to genetic convergence. Here we study a population of a hybrid species, the Italian sparrow (Passer italiae), before and after it came into secondary contact with one of its parent species, the Spanish sparrow (P. hispaniolensis), in 2013. We demonstrate clear consequences of interspecific competition: Italian sparrows became outcompeted from a popular feeding site by its parent species, resulting in poorer body condition and a significant drop in population size. Although no significant morphological change could be detected, after only 3 years of sympatry the Italian sparrows had diverged significantly from the Spanish sparrows across a set of 81 protein coding genes. These temporal genetic changes are mirrored by genetic divergence observed in older sympatric Italian sparrow populations within the same area of contact. Compared to microallopatric birds, sympatric ones are genetically more diverged from Spanish sparrows. Interestingly, all six significant outlier genes in the temporal or spatial comparison (i.e. those showing the greatest divergence from Spanish sparrows) have been found to be associated with learning and neural development in other species.

近缘物种间的次生接触（secondary contact）可产生遗传层面的效应。对必需资源的竞争可引发可遗传性状的分化，进而降低种间竞争，最终加剧遗传分化；反之，杂交与回交（backcrossing）则可导致遗传趋同。本研究针对杂交物种意大利麻雀（Passer italiae）的一个种群，追踪了2013年其与亲本之一西班牙麻雀（P. hispaniolensis）发生次生接触前后的动态变化。研究证实了种间竞争的显著效应：意大利麻雀被其亲本物种排挤离开一处热门觅食地，进而导致其身体状况恶化、种群规模大幅下降。尽管未检测到显著的形态学变化，但仅经过3年的同域共存（sympatry），意大利麻雀便在81个蛋白质编码基因的序列上与西班牙麻雀出现了显著分化。这种随时间推移产生的遗传分化模式，与同一片接触区域内更古老的同域意大利麻雀种群所观测到的遗传分化结果相一致。与微异域分布（microallopatric）的个体相比，同域分布的意大利麻雀在遗传层面与西班牙麻雀的分化程度更高。值得注意的是，在时间或空间维度的比较中，全部6个显著离群基因（即与西班牙麻雀分化程度最高的基因）均被证实与其他物种的学习行为及神经发育密切相关。