Data from: Can alternative mating tactics facilitate introgression across a hybrid zone by circumventing female choice?

Reproductive barriers and divergence in species' mate recognition systems underlie major models of speciation. However, hybridization between divergent species is common, and classic mechanisms to explain permeable reproductive barriers rarely consider how an individual may attain reproductive success. Alternative mating tactics exist in various forms across animal taxa. Such tactics may allow poorer quality individuals to gain mating opportunities and facilitate introgression either through asymmetrical positive selection, or by circumventing female choice altogether in areas of secondary contact. One such tactic is satellite behaviour in frogs, where silent males perch near advertisers in an attempt to intercept females. To test whether such satellite male tactics are context-dependent and favoured by hybrids, we genotyped and quantified the morphology of 80 male spring peeper (Pseudacris crucifer) individuals involved in caller-satellite associations from a secondary contact zone between two intraspecific mitochondrial lineages. Irrespective of population, satellite behaviour was best predicted by size but not body condition. Within the contact zone, pure individuals showed a significantly greater probability of being active callers, whereas hybrids of one lineage were more likely to adopt the satellite tactic. We suggest that satellite behaviour in P. crucifer promotes introgression, breaks-down reproductive isolating barriers, and contributes to asymmetrical introgression in this secondary contact zone. Alternative mating tactics may thus be an underexplored but important alternative to oft-discussed causes of genetic discordance found in hybrid zones.生殖隔离（reproductive barriers）与物种配偶识别系统的分化，是主流物种形成模型的核心基础。然而，分化物种间的杂交（hybridization）现象颇为常见，而解释可渗透生殖屏障的经典机制，却极少关注个体如何实现繁殖成功。替代交配策略（alternative mating tactics）在多个动物类群中以多样形式存在，此类策略可让质量欠佳的个体获得交配机会，并通过不对称正向选择（asymmetrical positive selection），或是在次生接触带（secondary contact zone）中完全绕过雌性选择（female choice），从而促进基因渐渗（introgression）。蛙类的卫星行为便是其中一种策略：沉默的雄性个体停靠在鸣唱广告雄性（advertisers）附近，试图拦截雌性个体。为验证此类雄性卫星行为是否具有情境依赖性，且是否更受杂交个体青睐，我们对来自两个种内线粒体谱系（mitochondrial lineages）次生接触带内、参与鸣唱-卫星行为关联的80只雄性春雨蛙（spring peeper, *Pseudacris crucifer*）个体进行了基因分型，并量化了其形态特征。无论所属种群如何，卫星行为的最佳预测因子均为体型大小，而非身体状况。在该接触带内，纯合个体（pure individuals）表现出显著更高的主动鸣唱概率，而携带单一线粒体谱系的杂交个体则更倾向于采用卫星策略。我们认为，春雨蛙的卫星行为可促进基因渐渗、打破生殖隔离屏障，并在该次生接触带中促成不对称基因渐渗。由此可见，替代交配策略或许是一种尚未被充分探索的重要机制，可用于解释杂交带（hybrid zones）中频繁被讨论的遗传不一致现象。