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.

长距离迁徙鸟类从定义上便具备极强的移动能力，但这类迁徙行为是否会促成高水平基因交流，进而形成实质上的泛交（panmictic）全球种群结构，目前仍缺乏明确认知。例如，对特定迁徙路线的忠实性，可能会加剧迁徙物种的遗传分化。本研究以凤头潜鸭（Aythya fuligula）为研究对象，该物种为长距离迁徙鸟类，其繁殖分布区在欧亚大陆范围内大体连续。基于地理上相互分隔的越冬区域，此前已有学者提出存在纵向取向的不同迁徙通道（flyway），且环志数据为此提供了实证支持。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，获取了其线粒体控制区（mitochondrial control region）序列以及多位点微卫星（microsatellite）基因型，其中包含部分感染高致病性禽流感病毒H5N1的个体。两种分子标记均显示繁殖地间存在显著遗传分化，但母系遗传的线粒体DNA的F_ST值约为双亲遗传的核标记的10倍。此前假设的欧洲与亚洲迁徙通道间的遗传分化程度，与各大陆内部的分化程度相近；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忠实性，尤其是雌性个体，但越冬地存在广泛的种群混合现象。可通过多种情景解释欧亚两地未出现明显遗传分化的现象，例如近期种群范围扩张后的非平衡状态，或是当前存在跨越假设迁徙分界的基因交流。