Data from: Mechanical reproductive isolation facilitates parallel speciation in western North American scincid lizards

Mechanical reproductive barriers have been dismissed as a major driver of animal speciation, yet the extent to which such barriers cause reproductive isolation in most animal groups is largely unknown and rarely tested. In this study, we used hierarchical Bayesian modeling of mate compatibility experiments to show that body size divergence in lizards of the Plestiodon skiltonianus complex contributes to reproductive isolation in at least three ways: males preferably court females that are more similar in size, females reject males that are highly divergent in size, and that the size difference of a male and female in copula constrains the ability to align the genitalia for intromission. We used a predictive model to estimate the contributions of behavioral and mechanical barriers to reproductive isolation between populations with differing degrees of size divergence. This model shows that the mechanical barrier is more important than the behavioral barriers at small and intermediate degrees of size divergence, suggesting that it acts earlier during speciation. As correlated divergence in size and ecology is common in animals, similar constraints imposed by the geometry of the mating posture may apply to a variety of major animal lineages and merit further attention in speciation research.长期以来，机械生殖隔离机制被排除在动物物种形成的主要驱动力之外，但这类机制在多数动物类群中造成生殖隔离的具体程度仍鲜为人知且极少得到实证检验。本研究通过对配偶兼容性实验开展分层贝叶斯建模（hierarchical Bayesian modeling），证实五线石龙子（Plestiodon skiltonianus）复合类群的体型分化可通过至少三种途径推动生殖隔离：雄性优先向体型更为相近的雌性求偶；雌性会排斥体型差异过大的雄性；以及处于交配状态的雌雄个体间的体型差，会限制二者对齐生殖器以完成插入式交配的能力。我们借助预测模型，估算了行为隔离机制与机械隔离机制对不同体型分化程度种群间生殖隔离的贡献度。该模型显示，在体型分化程度较小和中等的种群间，机械隔离机制的作用要大于行为隔离机制，这表明机械隔离在物种形成过程中启动更早。由于体型与生态位的协同分化在动物类群中十分普遍，因此交配体位几何特征所带来的类似约束，或许适用于诸多主要动物演化支系，值得物种形成研究领域进一步关注。