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.

从定义而言，长距离迁徙物种具有极强的移动能力，但此类迁徙是否会带来高水平的基因流，并形成本质上泛交（panmictic）的全球种群结构，目前仍不甚明晰。迁徙物种的遗传分化可能因个体对特定迁徙路径的保真行为而加剧。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，其繁殖种群在欧亚大陆范围内呈大体连续的分布格局。此前基于地理分隔的越冬区域，学界已提出存在不同的纵向迁徙通道（flyway）假说，且该假说得到了环志数据的佐证。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线粒体控制区序列测序，以及多位点微卫星（microsatellite）基因型分型，其中包含部分感染高致病性禽流感病毒H5N1的个体。两类分子标记均显示繁殖地间存在显著的遗传分化，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。假说中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当；总体而言，遗传分化与地理距离并无关联。两类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。本研究结果显示，凤头潜鸭存在一定的繁殖地保真行为，尤以雌性个体为甚，但越冬地存在广泛的种群混合现象。有多种假说可解释欧亚两地未出现显著遗传分化的现象，包括近期种群范围扩张后的非平衡状态，或是当前存在跨越假说中迁徙分界的基因流。