Data from: Rise and fall of a hybrid zone: implications for the roles of aggression, mate choice, and secondary succession

Hybridization can be an important evolutionary force by generating new species and influencing evolution of parental species in multiple ways, including introgression and the consequences of hybrid vigor. Determining the ecological processes underlying evolution in hybrid zones is difficult however because it requires examining changes in both genotypic frequencies over time and corresponding ecological information, data that are rarely collected together. Here, we describe genetic and ecological aspects of a hybrid zone between the Eastern Fence Lizard, Sceloporus undulatus, and the Florida Scrub Lizard, Sceloporus woodi, occurring over at least 23 generations. The hybrid zone, discovered greater than 35 years ago using morphological characters, originally consisted of nearly even proportions of parental species and hybrids. Now, using genetic markers (species-diagnostic mtDNA sites and 6 nDNA microsatellite loci across a total of n = 117 individuals), we confirm not only that hybridization occurred but also that subsequent backcrossing has resulted in highly introgressed hybrids, with many hybrids containing mitochondrial DNA from one species on a nuclear DNA background of the other. Ecological aspects explaining these shifts in genetic composition include female mate choice, changes in habitat associated with secondary succession, and, most strongly, a hierarchy of male territorial advantage—ecological mechanisms likely to be involved in the emergence and disappearance of many animal hybrid zones. Our results suggest that genetic assimilation is not a significant threat to either species and that rather transient hybrid zones such as this may serve to increase genetic diversity and are candidates for causing genetic discordance in phylogeographic analyses.杂交（hybridization）可通过产生新物种，并以多种途径影响亲本物种的演化进程——包括渐渗（introgression）与杂种优势（hybrid vigor）所介导的效应，从而成为一类重要的演化驱动力。然而，解析杂交带（hybrid zone）内演化背后的生态机制极具挑战：此类研究需同时追踪种群基因型频率（genotypic frequencies）随时间的动态变化，以及对应的生态数据，而这类同步采集的整合数据极为稀缺。本研究描述了分布于至少23个世代跨度内的东部栅栏蜥蜴（*Sceloporus undulatus*）与佛罗里达灌丛蜥蜴（*Sceloporus woodi*）之间的杂交带的遗传与生态特征。该杂交带于35年前通过形态学性状被首次发现，初始状态下亲本物种与杂交个体的种群占比近乎均等。本研究通过涵盖共计117个个体的遗传标记——物种诊断性线粒体DNA（mtDNA）位点与6个核DNA（nDNA）微卫星位点（microsatellite loci）——不仅证实了杂交事件的发生，还发现后续的回交（backcrossing）已产生了高度渐渗的杂交个体：诸多杂交个体的线粒体DNA源自其中一个物种，但其核基因组背景却属于另一物种。可解释该遗传组成转变的生态机制包括：雌性配偶选择、与次生演替相关的生境变迁，以及最为显著的雄性领地优势层级——这类生态机制大概率参与了诸多动物杂交带的形成与消亡过程。本研究结果显示，遗传同化（genetic assimilation）并未对任一物种构成显著威胁；而此类短暂存续的杂交带，反而可能提升种群遗传多样性，且有可能在系统地理学分析（phylogeographic analyses）中引发遗传不一致性。