Contact zones present unique opportunities to investigate ecological divergence, reproductive barriers, and gene flow between species. The two-lined salamander (Eurycea bislineata) species complex is a group of semiaquatic plethodontid salamanders with a reticulate evolutionary history that reflects the reorganization of river drainage basins. Although evidence for widespread, ancient introgression suggests an absence of reproductive isolating mechanisms in the early evolutionary history of the group, modern contact zones reveal a broader diversity of outcomes—with some putative species pairs occurring in sympatry and others exhibiting narrow hybrid zones. Here, we used RADcap data to investigate gene flow and ecological divergence in replicate contact zones between two species in the Appalachian foothills. Our results demonstrate that gene flow between these species is absent or rare, and larvae show strong, fine-scale ecological segregation among riffles, runs, and pools in streams. These results reinforce the more ambiguous conclusions of previous studies that suggested the evolutionary distinctiveness of these two species and underscore the importance of ecological factors in shaping local distributions.

接触区为调查物种之间的生态差异，生殖障碍和基因流提供了独特的机会。两线sal（Eurycea bislineata）物种复合体是一组半水生的齿状sal，其网状演化历史反映了流域盆地的重组。尽管有证据表明广泛的，古老的基因渗入表明该群体的早期进化史上没有生殖隔离机制，但现代接触区显示出更广泛的结果多样性，其中一些假定的物种对出现在共生系统中，而另一些则显示出狭窄的杂种区。在这里，我们使用RADcap数据研究了阿巴拉契亚山麓丘陵中两个物种之间重复接触区域中的基因流动和生态多样性。我们的研究结果表明，这些物种之间的基因流不存在或很少，幼虫显示出溪流，河道和水池之间强大的，精细的生态隔离。