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.

溪流与河川的网络架构制约着淡水生物的演化、种群动态与生态过程。这种统一的网络架构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。我们以美国爱达荷州与蒙大拿州溪流网络中的兼性幼态延续型爱达荷巨螈（*Dicamptodon aterrimus*）为研究对象，分析其种群遗传结构与基因流模式。我们利用微卫星数据，通过两种方式检验种群结构模型：一是分析溪流网络中遗传变异的层级分化格局，二是检验沿溪流廊道与陆地通路的遗传距离隔离效应。我们在三个流域的集水区内对溪流进行重复采样，结果显示层级尺度对种群遗传结构与基因流具有显著影响。分子方差分析（Analysis of Molecular Variance, AMOVA）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信号，这表明基因流仅在更小的尺度（集水区内部而非集水区之间）能够抵消遗传漂变的影响。本研究结果证实了溪流网络对蝾螈种群结构与遗传分化的强烈影响，且不同层级尺度下的影响效应存在显著差异。