Data from: Seeking signatures of reinforcement at the genetic level: a hitchhiking mapping and candidate gene approach in the house mouse

Reinforcement is the process by which prezygotic isolation is strengthened as a response to selection against hybridisation. Most empirical support for reinforcement comes from the observation of its possible phenotypic signature: an accentuated degree of prezygotic isolation in the hybrid zone as compared to allopatry. Here, we implemented a novel approach to this question by seeking for the signature of reinforcement at the genetic level. In the house mouse, selection against hybrids and enhanced olfactory-based assortative mate preferences are observed in a hybrid zone between the two European subspecies Mus musculus musculus and M. m. domesticus, suggesting a possible recent reinforcement event. To test for the genetic signature of reinforcing selection and identify genes involved in sexual isolation, we adopted a hitchhiking mapping approach targeting genomic regions containing candidate genes for assortative mating in mice. We densely scanned these genomic regions in hybrid zone and allopatric samples using a large number of fast evolving microsatellite loci that allow the detection of recent selection events. We found a handful of loci showing the expected pattern of significant reduction of variability in populations close to the hybrid zone and showing assortative odour preference in mate choice experiments as compared to populations further away and displaying no such preference. These loci lie close to genes that we pinpoint as testable candidates for further investigation.

强化作用（Reinforcement）指为应对针对杂交的选择压力而增强合子前生殖隔离（prezygotic isolation）的进化过程。目前关于强化作用的多数实证依据，均来自对其潜在表型特征的观测：与异域种群相比，杂交带内的合子前生殖隔离程度显著提升。本研究针对这一科学问题，采用了全新的研究思路，旨在从遗传层面探寻强化作用的特征信号。针对小家鼠的研究中，在两个欧洲亚种——小家鼠东欧亚种（Mus musculus musculus）与西欧小家鼠（M. m. domesticus）的杂交带内，已观测到抗杂交选择与强化的嗅觉型选型交配偏好，提示该区域可能发生过近期的强化作用事件。为检测强化选择的遗传特征信号，并鉴定参与性隔离的相关基因，本研究采用了搭便车作图（hitchhiking mapping）策略，靶向定位小鼠中与选型交配相关的候选基因所在的基因组区域。研究团队利用大量快速进化的微卫星位点（microsatellite loci），对杂交带与异域种群的上述基因组区域开展高密度扫描，以检测近期发生的选择事件。结果显示，相较于远离杂交带且未表现出嗅觉选型交配偏好的种群，靠近杂交带且在交配选择实验中呈现出选型气味偏好的种群中，有多个位点表现出预期的遗传多样性显著降低的模式。这些位点附近的基因，可作为后续研究的可验证候选基因。