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.

江河溪流的网络架构制约着淡水生物的演化、种群动态与生态过程。这种统一的架构特性也使得溪流网络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系统。本研究以美国爱达荷州与蒙大拿州溪流网络中的兼性幼态型爱达荷巨螈（*Dicamptodon aterrimus*）为研究对象，探究其种群遗传结构与基因流模式。我们借助微卫星（microsatellite）标记数据，通过两项实验检验种群结构模型：一是分析溪流网络中遗传变异的层级分布格局，二是对比检验沿溪流廊道与陆地通路的距离依赖型遗传分化。我们对三个河流流域内的集水区及其中的溪流进行重复采样，结果显示层级尺度对种群遗传结构与基因流存在显著影响。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，但集水区间的遗传分化对整体结构的影响最为显著。集水区内存在显著的距离隔离效应，且溪流内距离是遗传分化的强预测因子。遗传分化格局表明，集水区内溪流间的分化由有限的迁移所驱动，这与种群结构的溪流层级模型相符。然而，流域内集水区间以及不同流域间均未检测到迁移事件，这表明基因流仅能在更小尺度（集水区内部而非集水区之间）抵消遗传漂变的作用效果。本研究结果证实，溪流网络对蝾螈的种群结构与遗传分化存在强烈影响，且在不同层级尺度下呈现出差异化的作用效果。