Data from: Scale-dependent genetic structure of the Idaho giant salamander (Dicamptodon aterrimus) in stream networks

The network architecture of streams and rivers constrains evolutionary, demographic, and ecological processes of freshwater organisms. This consistent architecture also makes stream networks useful for testing general models of population genetic structure and the scaling of gene flow. We examined genetic structure and gene flow in the facultatively paedomorphic Idaho giant salamander, Dicamptodon aterrimus, in stream networks of Idaho and Montana, USA. We used microsatellite data to test population structure models by (1) examining hierarchical partitioning of genetic variation in stream networks and (2) testing for genetic isolation by distance along stream corridors versus overland pathways. Replicated sampling of streams within catchments within three river basins revealed that hierarchical scale had strong effects on genetic structure and gene flow. AMOVA identified significant structure at all hierarchical scales (among streams, among catchments, among basins), but divergence among catchments had the greatest structural influence. Isolation by distance was detected within catchments, and in-stream distance was a strong predictor of genetic divergence. Patterns of genetic divergence suggest that differentiation among streams within catchments was driven by limited migration, consistent with a stream hierarchy model of population structure. However, there was no evidence of migration among catchments within basins, or among basins, indicating that gene flow only counters the effects of genetic drift at smaller scales (within rather than among catchments). These results show the strong influence of stream networks on population structure and genetic divergence of a salamander, with contrasting effects at different hierarchical scales.溪流与河流构成的河网（stream networks）结构会限制淡水生物的演化、种群统计与生态过程。这种统一的结构特性也使得河网成为检验种群遗传结构通用模型以及基因流尺度效应的理想研究体系。我们针对美国爱达荷州与蒙大拿州境内河网中的兼性幼态延续型（facultatively paedomorphic）爱达荷巨蝾螈（Dicamptodon aterrimus）展开研究，分析其种群遗传结构与基因流情况。我们借助微卫星标记（microsatellite）数据，通过两项实验检验种群遗传结构模型：一是分析河网内遗传变异的层级划分模式，二是检验沿溪流廊道与陆通路的遗传距离隔离效应。对三个流域内集水区中的溪流进行重复采样后发现，层级尺度对种群遗传结构与基因流具有显著影响。分子方差分析（AMOVA）结果显示，所有层级尺度（溪流间、集水区间、流域间）均存在显著的遗传结构，但集水区间的分化对遗传结构的影响最为显著。集水区内部检测到距离隔离效应，且溪流内距离是遗传分化的强预测因子。遗传分化模式表明，集水区内溪流间的分化由有限的迁移所驱动，这与种群结构的河网层级模型相符。然而，流域内集水区间以及流域间均未检测到迁移信号，这表明基因流仅能在更小的尺度（集水区内部而非集水区间）抵消遗传漂变的影响。本研究结果证实，河网对蝾螈的种群结构与遗传分化具有显著影响，且不同层级尺度下的效应存在显著差异。