Data from: Genomic signatures of geographic isolation and natural selection in coral reef fishes

The drivers of speciation remain among the most controversial topics in evolutionary biology. Initially, Darwin emphasized natural selection as a primary mechanism of speciation, but the architects of the modern synthesis largely abandoned that view in favour of divergence by geographic isolation. The balance between selection and isolation is still at the forefront of the evolutionary debate, especially for the world's tropical oceans where biodiversity is high, but isolating barriers are few. Here, we identify the drivers of speciation in Pacific reef fishes of the genus Acanthurus by comparative genome scans of two peripheral populations that split from a large Central-West Pacific lineage at roughly the same time. Mitochondrial sequences indicate that populations in the Hawaiian Archipelago and the Marquesas Islands became isolated approximately 0.5 Ma. The Hawaiian lineage is morphologically indistinguishable from the widespread Pacific form, but the Marquesan form is recognized as a distinct species that occupies an unusual tropical ecosystem characterized by upwelling, turbidity, temperature fluctuations, algal blooms and little coral cover. An analysis of 3737 SNPs reveals a strong signal of selection at the Marquesas, with 59 loci under disruptive selection including an opsin Rh2 locus. While both the Hawaiian and Marquesan populations indicate signals of drift, the former shows a weak signal of selection that is comparable with populations in the Central-West Pacific. This contrast between closely related lineages reveals one population diverging due primarily to geographic isolation and genetic drift, and the other achieving taxonomic species status under the influence of selection.

物种形成的驱动机制始终是进化生物学领域最具争议的核心议题之一。最初，达尔文将自然选择视作物种形成的首要机制，但现代综合进化论的奠基者们大多摒弃了这一观点，转而支持地理隔离驱动的种群分化。选择与隔离之间的平衡至今仍是进化生物学争论的前沿话题，尤其是在生物多样性极高但隔离屏障稀缺的全球热带海洋区域。
本研究通过对两个近乎同时从泛中西太平洋大种群中分化而来的边缘种群开展比较基因组扫描，解析刺尾鱼属（Acanthurus）太平洋礁栖鱼类的物种形成驱动因素。
线粒体序列数据表明，夏威夷群岛与马克萨斯群岛的种群约在0.5百万年前发生地理隔离。夏威夷种群与广泛分布的太平洋广布种群形态上难以区分，但马克萨斯种群被认定为独立物种，其栖息的热带生态系统具有独特特征：存在上升流、水体浊度变化、温度波动、藻华现象且珊瑚覆盖率极低。
对3737个单核苷酸多态性（SNPs）的分析显示，马克萨斯种群存在显著的选择信号，共有59个位点受到歧化选择，其中包含视蛋白Rh2位点。
尽管夏威夷种群与马克萨斯种群均表现出遗传漂变的信号，但前者仅呈现微弱的选择信号，其强度与泛中西太平洋的种群相当。这一近缘类群间的分化差异表明，一个种群的分化主要由地理隔离与遗传漂变驱动，而另一个种群则在选择压力的作用下达到了分类学上的物种等级。