A headwater or river capture is a phenomenon commonly invoked to explain the absence of reciprocal monophyly of genetic lineages among isolated hydrographic basins in freshwater fish. Under the assumption of river capture, a secondary contact between populations previously isolated in different basins explains the observed genetic pattern. However, the absence of reciprocal monophyly could also arise under population isolation through the retention of ancestral of polymorphisms. Here, we applied an approximate Bayesian computation (ABC) framework for estimating the relative probability of scenarios with and without secondary contact. We used Cnesterodon decemmaculatus as a study model because of the multiple possible cases of river capture and the demographic parameters estimated in a previous mitochondrial DNA study that are useful for simulating scenarios to test both hypotheses using the ABC framework. Our results showed that, in general, mitochondrial DNA is useful for distinguishing between these alternative demographic scenarios with reasonable confidence, but in extreme cases (e.g. recent divergence or large population size) there is no power to discriminate between scenarios. Testing hypotheses of drainage rearrangement under a statistically rigorous framework is fundamental for understanding the evolution of freshwater fish fauna as a complement to, or in the absence of, geological evidence.

中文翻译：

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河流捕获或祖先多态性：使用近似贝叶斯计算的淡水鱼实证遗传测试

上游水源捕获或河流捕获是一种现象，通常被用来解释淡水鱼中孤立的水文盆地之间遗传谱系互不相干的现象。在捕获河流的假设下，先前在不同流域中隔离的种群之间的次要接触解释了观察到的遗传模式。但是，在种群隔离下，通过保留多态祖先也可能会出现互惠的单亲现象。在这里，我们应用了近似贝叶斯计算（ABC）框架来估计有和没有辅助接触的情况下的相对概率。我们使用了Cnesterodon decemmaculatus之所以将其作为研究模型，是因为有许多可能的河流捕获案例，以及先前的线粒体DNA研究中估计的人口统计学参数，这些参数可用于模拟使用ABC框架测试两种假设的方案。我们的结果表明，一般而言，线粒体DNA可用于以合理的置信度来区分这些替代的人口统计学场景，但在极端情况下（例如，最近的分歧或人口众多），无法区分场景。在统计学上严格的框架下测试排水重新布置的假设对于理解淡水鱼动物群的进化是对地质证据的补充或缺乏地质证据的基础。