Data from: Phenotypic and genotypic variation across a stable white-eye (Zosterops sp.) hybrid zone in central South Africa

The interbreeding of two species after a period of separation (secondary contact) most often results in stable areas of hybridization or tension zones characterized by selection against hybrid individuals. Three plumage forms of Zosterops meet and interbreed in central South Africa. Here we examine how phenotypic measures (biometric and plumage) and genotypic markers (mitochondrial and nuclear DNA) change through a putative hybrid zone located in the area where the ranges of the Orange River White-eye Zosterops pallidus and a subspecies of the Cape White-eye, Z. virens capensis, meet. Four of the five sequenced loci (ATP6, MUSK, GADPH and TGF-β2) showed strong divergence and differentiation between allopatric parental populations, whereas the sex-linked CHD1Z locus exhibited high homogeneity. Microsatellite data also distinguished between pure Z. pallidus and Z. v. capensis populations. Together, the nuclear data (introns and microsatellites) identified at least 12 hybrid individuals as later generation hybrids (i.e. F2 or backcrosses), and no F1-hybrids were detected. As genetic incompatibility does not appear to play a role in restricting this stable hybrid zone, it is likely that environmental conditions including biome type and edge effect are constraining hybrid zone movement.

两个物种经历一段时期生殖隔离后再度接触（二次接触，secondary contact）时发生的种间杂交，通常会形成稳定的杂交区域或张力区，此类区域的核心特征为对杂交个体存在选择淘汰作用。绣眼鸟属（Zosterops）的三种羽色型在南非中部区域相遇并发生杂交。本研究聚焦于奥兰治河绣眼鸟（Zosterops pallidus）与开普绣眼鸟的亚种Z. virens capensis的分布区交汇地带的疑似杂交带（hybrid zone），旨在探究表型指标（包括形态测量与羽色特征）以及基因型标记（线粒体DNA与核DNA）在该杂交带内的变化规律。在测序获得的5个基因座中，ATP6、MUSK、GADPH与TGF-β2这4个基因座在异域亲本种群（allopatric parental population）间表现出显著的遗传分化，而性连锁基因座CHD1Z则呈现高度的遗传均一性。微卫星标记（microsatellite）数据同样能够区分纯合的Z. pallidus种群与Z. v. capensis种群。结合核基因组数据（内含子序列与微卫星标记）的分析结果，研究人员鉴定出至少12个杂交个体属于晚世代杂交类群（即F2代或回交后代），未检测到F1代杂交个体。鉴于遗传不相容性并未在限制该稳定杂交带存续的过程中发挥作用，推测包括生物群系类型与边缘效应（edge effect）在内的环境条件，才是制约该杂交带移动的关键因素。