Assortative mating and the maintenance of population structure in a natural hybrid zone

Understanding the factors that give rise to natural hybrid zones and govern their dynamics and structure is important to predicting the evolutionary consequences of hybridization. Here we use a combination of multi-generational population genetic data, mating patterns from a natural population, behavioral assays, and mark-recapture data within clinal hybrid zones of the genus Xiphophorus to test the role of assortative mating in maintaining population structure and the potential for ongoing genetic exchange between heterospecifics. Our data demonstrate that population structure is temporally robust and driven largely by assortative mating stemming from pre-copulatory isolation between pure species. Furthermore, mark-recapture data revealed that rates of migration within the same stream reach are far below the level needed to support population structure. Contrasting with many empirical studies of natural hybrid zones, there appeared to be no hybrid male dysfunction nor discrimination ag...

探明自然杂交带的形成动因、动态调控机制与结构维持规律，对于预测杂交演化后果具有重要理论意义。本研究结合多世代种群遗传数据、自然种群交配模式观测数据、行为学实验数据，以及剑尾鱼属（Xiphophorus）渐变杂交带（clinal hybrid zones）内的标记-重捕（mark-recapture）数据，检验了选型交配（assortative mating）在种群结构维持中的作用，以及异种个体（heterospecifics）间持续遗传交流的潜在可能性。研究数据表明，该种群结构在时间维度上保持稳定，且主要由纯种间交配前隔离（pre-copulatory isolation）所介导的选型交配所驱动。此外，标记-重捕数据显示，同一河段内的个体迁移率远低于维持种群结构所需的临界水平。与诸多自然杂交带的实证研究不同，本研究未发现杂交雄性存在生殖功能缺陷，亦未观察到歧视性……