Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA.
Mol Ecol. 2010 Mar;19(5):898-909. doi: 10.1111/j.1365-294X.2010.04541.x. Epub 2010 Feb 8.
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 (i) examining hierarchical partitioning of genetic variation in stream networks; and (ii) testing for genetic isolation by distance along stream corridors vs. 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.
河流网络的结构限制了淡水生物的进化、种群和生态过程。这种一致的结构也使得河流网络成为测试种群遗传结构和基因流动尺度的一般模型的有用工具。我们在美国爱达荷州和蒙大拿州的河流网络中研究了兼性幼态型爱达荷巨型蝾螈（Dicamptodon aterrimus）的遗传结构和基因流动。我们使用微卫星数据通过以下两种方法来检验种群结构模型：（i）检验河流网络中遗传变异的分层划分；（ii）检验沿河道与越岭路径的遗传隔离。在三个流域内的集水区内对河流进行了重复采样，结果表明层次尺度对遗传结构和基因流动有很强的影响。amova 鉴定了所有层次尺度上（河流之间、集水区之间、流域之间）的显著结构，但集水区之间的分歧具有最大的结构影响。在集水区内检测到了由距离隔离的现象，而河道内的距离是遗传分化的重要预测因子。遗传分化模式表明，集水区内河流之间的分化是由有限的迁移驱动的，这与种群结构的河流层次模型一致。然而，没有证据表明流域内的集水区之间或流域之间存在迁移，这表明基因流动仅在较小的尺度上（而不是在集水区之间）抵消遗传漂变的影响。这些结果表明河流网络对蝾螈种群结构和遗传分化有很强的影响，在不同的层次尺度上有相反的影响。
