Data from: Breeding site fidelity and winter admixture in a long-distance migrant, the tufted duck (Aythya fuligula)

Long-distance migrants are, by definition, highly mobile but it is poorly understood if this leads to high rates of gene flow and an essentially panmictic global population structure. Genetic divergence in migratory species could be promoted, for example, by fidelity to distinct migratory pathways. In this study, we investigate the population genetic structure of tufted duck (Aythya fuligula), a long-distance migrant with a largely continuous breeding distribution across Eurasia. Distinct, longitudinally oriented flyways have been postulated based on geographically disjunct wintering areas and are supported by evidence from ringing data. We generated sequences of the mitochondrial control region and multi-locus microsatellite genotypes for several hundreds of samples from the European and Asian breeding and wintering grounds including some individuals infected with highly pathogenic avian influenza virus H5N1. Significant differentiation between breeding sites was observed for both marker types, but F_ST values were approximately 10 times higher for maternally inherited mitochondrial DNA than for biparentally transmitted nuclear markers. The genetic differentiation between the postulated European and Asian flyways was similar to that observed within continents and, in general, genetic divergence was not associated with geographic distance. Neither marker type showed evidence of genetic substructure among aggregations on the European wintering grounds. Our results suggest some breeding site fidelity, especially in females, but extensive population admixture on the wintering grounds. Several scenarios may explain the observed lack of genetic divergence between Europe and Asia including non-equilibrium conditions following a recent range expansion or contemporary gene flow across the postulated migratory divides.从定义上看，长途迁徙鸟类具备极强的移动能力，但学界目前仍未明确，这种高移动性是否会催生高水平的基因流，进而形成本质上泛交（panmictic）的全球种群结构。迁徙物种的遗传分化可能由多种因素促成，例如个体对特定迁徙路径的忠实性。本研究以凤头潜鸭（Aythya fuligula）为研究对象，该物种为长途迁徙鸟类，其繁殖分布区在欧亚大陆范围内整体呈连续状态。此前已有研究基于地理隔离的越冬地提出了沿经度方向分布的不同迁徙通道（flyway），且环志数据为该假说提供了支撑证据。我们对采自欧亚大陆繁殖地与越冬地的数百份样本进行了分析，其中部分个体感染了高致病性禽流感病毒H5N1，最终获得了线粒体控制区序列与多位点微卫星基因型数据。两种分子标记均显示繁殖地之间存在显著遗传分化，但母系遗传的线粒体DNA的F_ST值约为双亲遗传核标记的10倍。被假说划分的欧亚迁徙通道之间的遗传分化，与两大洲内部的遗传分化水平相当；总体而言，遗传分化与地理距离并无关联。两种分子标记均未在欧洲越冬地的种群集群中检测到遗传亚结构。本研究结果表明，凤头潜鸭存在一定的繁殖地归巢习性，雌性个体的该习性尤为显著，但越冬地存在广泛的种群混合现象。有多种情景可解释欧亚大陆间未检测到明显遗传分化的现象，例如近期种群范围扩张后尚未达到遗传平衡状态，或是当前存在跨越假说中迁徙通道分界的基因流。