Context

Rivers, landscape, and climate can alter patterns of gene flow and consequently, shape intraspecific genetic variation. While rivers are predicted to halt gene flow in terrestrial species, they may facilitate migration for aquatic species. Amphibians are usually seen as water-dependent, yet multiple studies have indicated that rivers exert a barrier effect on these organisms.

Objectives

In this study, we investigated the effects of rivers and other abiotic factors, such as climate and geography on genetic variation of a highly aquatic frog (Pseudis tocantins) inhabiting central Brazil.

Methods

We sequenced fragments of one mitochondrial and two nuclear genes of 179 individuals of P. tocantins from 19 localities along the Tocantins-Araguaia Basin in Brazil and used Generalized Dissimilarity Modeling (GDM) to test the role of rivers, landscape, and climate features on its genetic differentiation. Next, we tested three scenarios of migration along the Tocantins-Araguaia Basin using approximate Bayesian computation (ABC).

Results

We found that genetic differentiation among localities is mostly explained by the influence of river connectivity. Conversely, elevation, slope, and past and current climate have little or no impact on genetic differentiation. Furthermore, our results show that patterns of migration took place directionally, from upstream to downstream sites.

Conclusions

Rivers have shaped patterns of intraspecific diversity in P. tocantins by acting as the most important facilitator of gene flow. Therefore, we suggest that future research should include the role of rivers as a facilitator of gene flow, especially for those species that are associated with aquatic environments.

中文翻译：

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河流高速公路假说：河流是水生矛盾蛙 Pseudis tocantins（Anura，Hylidae）基因流动的关键中介

语境

河流、景观和气候可以改变基因流动的模式，从而形成种内遗传变异。虽然预计河流会阻止陆地物种的基因流动，但它们可能会促进水生物种的迁移。两栖动物通常被视为依赖水，但多项研究表明河流对这些生物产生屏障作用。

目标

在这项研究中，我们调查了河流和其他非生物因素（如气候和地理）对栖息在巴西中部的高度水生青蛙（Pseudis tocantins）遗传变异的影响。

方法

我们对来自巴西 Tocantins-Araguaia 盆地 19 个地点的 179 个P. tocantins个体的一个线粒体和两个核基因的片段进行了测序，并使用广义差异建模 (GDM) 来测试河流、景观和气候特征对其的作用。遗传分化。接下来，我们使用近似贝叶斯计算 (ABC) 测试了沿 Tocantins-Araguaia 盆地的三种迁移方案。

结果

我们发现地方之间的遗传分化主要是由河流连通性的影响来解释的。相反，海拔、坡度以及过去和现在的气候对遗传分化几乎没有影响。此外，我们的结果表明，迁移模式是定向发生的，从上游到下游站点。

结论

河流作为基因流动的最重要促进者，在P. tocantins 中塑造了种内多样性模式。因此，我们建议未来的研究应该包括河流作为基因流动促进者的作用，特别是对于那些与水生环境相关的物种。