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）指在不存在基因流（gene flow）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，在热带地区尤为突出。本研究以亚马孙生态交错带中的电鱼（electric fish）Steatogenys elegans为研究对象，探究其基于生态机制的分化过程。研究结合了系统发育学（phylogenetics）、基因组扫描（genome scans）与群体遗传学（population genetics），并采用新近开发的纳入选择作用的基于个体的进化景观遗传学（individual-based evolutionary landscape genetics）方法。该分析框架用于评估作为生物多样性驱动因子的地理因素与环境间趋异自然选择的相对贡献。本研究报道了两个亲缘关系密切的同域世系（sympatric lineages），它们印证了亚马孙大型水生生态交错带（即水化学特性差异显著的河流之间）的趋异选择如何可促成重复的生态介导物种形成。研究结果将生态梯度上的选择与生殖隔离建立了关联，我们提出基于水体颜色的选型交配（assortative mating）可能推动了这一分化过程。由生态驱动选择所产生的分化，凸显了在热带地区物种形成研究中考虑环境异质性的重要性。此外，本研究表明，在空间显式（spatially explicit）进化景观遗传学框架下开展生态物种形成研究，为探索自然选择中空间依赖性的各类潜在效应提供了重要的基础性第一步。