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流物理屏障的条件下，生殖隔离（reproductive isolation）与生态位分化（niche divergence）的演化过程。该过程是物种形成议题中最具争议的话题之一，在热带区域尤为突出。本研究以亚马逊生态交错带（Amazonian ecotone）中的电鱼（electric fish）*Steatogenys elegans*为研究对象，开展基于生态机制的分化研究。研究整合了系统发育学（phylogenetics）、基因组扫描（genome scans）与群体遗传学（population genetics）技术，并结合了一种新近开发的纳入选择效应的基于个体的进化景观遗传学方法（individual-based evolutionary landscape genetics approach）。该框架被用于评估地理因素与环境间的趋异自然选择（divergent natural selection）作为生物多样性驱动因子的相对贡献占比。本研究报道了两个亲缘关系密切且同域分布的支系（sympatric lineages），它们清晰展现了亚马逊主要水生生态交错带——即水化学特性差异显著的河流之间——的趋异选择如何能够引发经生态介导的重复式物种形成。研究结果将生态梯度上的选择作用与生殖隔离建立了关联，并提出基于水色的选型交配（assortative mating）可能是推动该分化过程的关键因素。由生态驱动的选择所产生的分化现象，凸显了在热带区域开展物种形成研究时，考量环境异质性的重要性。此外，本研究证实，将生态物种形成置于空间显式（spatially explicit）的进化景观遗传学框架下开展研究，可为探索自然选择中空间依赖性（spatial dependence）的多方面潜在影响提供重要的奠基性步骤。