Data from: Riverscape genetics identifies replicated ecological divergence across an Amazonian ecotone

Ecological speciation involves the evolution of reproductive isolation and niche divergence in the absence of a physical barrier to gene flow. The process is one of the most controversial topics of the speciation debate, particularly in tropical regions. Here, we investigate ecologically based divergence across an Amazonian ecotone in the electric fish, Steatogenys elegans. We combine phylogenetics, genome scans and population genetics with a recently developed individual-based evolutionary landscape genetics approach that incorporates selection. This framework is used to assess the relative contributions of geography and divergent natural selection between environments as biodiversity drivers. We report on two closely related and sympatric lineages that exemplify how divergent selection across a major Amazonian aquatic ecotone (i.e., between rivers with markedly different hydrochemical properties) may result in replicated ecologically mediated speciation. The results link selection across an ecological gradient with reproductive isolation and we propose that assortative mating based on water color may be driving the divergence. Divergence resulting from ecologically driven selection highlights the importance of considering environmental heterogeneity in studies of speciation in tropical regions. Furthermore, we show that framing ecological speciation in a spatially-explicit evolutionary landscape genetics framework provides an important first step in exploring a wide range of the potential effects of spatial dependence in natural selection.

生态物种形成（ecological speciation）指的是在不存在基因交流的物理屏障的情况下，生殖隔离与生态位分化的演化过程。该过程是物种形成研究领域争议最大的议题之一，在热带地区尤为突出。本研究以亚马孙生态交错带中的电鱼优雅裸背电鳗（Steatogenys elegans）为研究对象，开展基于生态过程的分化分析；我们将系统发育学、基因组扫描与种群遗传学方法，与新近开发的纳入选择作用的基于个体的演化景观遗传学分析框架相结合，借助该框架评估了地理因素与环境间趋异自然选择作为生物多样性驱动因子的相对贡献。本研究报道了两个亲缘关系密切且同域分布的支系，它们例证了亚马孙大型水生生态交错带（即水化学特征显著迥异的河流之间）的趋异选择如何可引发重复的生态介导型物种形成。研究结果将生态梯度上的选择作用与生殖隔离相联系，并提出基于水体颜色的选型交配可能是该分化过程的驱动因素。由生态驱动的选择所产生的分化，凸显了在热带地区物种形成研究中纳入环境异质性考量的重要性。此外，本研究表明，将生态物种形成置于空间显性演化景观遗传学分析框架中进行分析，可为探索自然选择中空间依赖性的各类潜在影响提供关键的第一步。