High gene flow is considered the norm for most marine organisms and is expected to limit their ability to adapt to local environments. Few studies have directly compared the patterns of differentiation at neutral and selected gene loci in marine organisms. We analysed a transcriptome-derived panel of 281 SNPs in Atlantic herring (Clupea harengus), a highly migratory small pelagic fish, for elucidating neutral and selected genetic variation among populations and to identify candidate genes for environmental adaptation. We analysed 607 individuals from 18 spawning locations in the northeast Atlantic, including two temperature clines (5-12 °C) and two salinity clines (5-35‰). By combining genome scan and landscape genetic analyses, four genetically distinct groups of herring were identified: Baltic Sea, Baltic-North Sea transition area, North Sea/British Isles and North Atlantic; notably, samples exhibited divergent clustering patterns for neutral and selected loci. We found statistically strong evidence for divergent selection at 16 outlier loci on a global scale, and significant correlations with temperature and salinity at nine loci. On regional scales, we identified two outlier loci with parallel patterns across temperature clines and five loci associated with temperature in the North Sea/North Atlantic. Likewise, we found seven replicated outliers, of which five were significantly associated with low salinity across both salinity clines. Our results reveal a complex pattern of varying spatial genetic variation among outlier loci, likely reflecting adaptations to local environments. In addition to disclosing the fine scale of local adaptation in a highly vagile species, our data emphasize the need to preserve functionally important biodiversity.

译文

高基因流动被认为是大多数海洋生物的常态,预计会限制它们适应当地环境的能力。很少有研究直接比较海洋生物中性基因位点和选定基因位点的分化模式。我们分析了转录组的281个SNP的转录组,该杂交组是高度迁移的小型中上层鱼类大西洋鲱鱼(Clupea harengus),用于阐明种群之间的中性和选择性遗传变异,并确定环境适应性候选基因。我们分析了来自东北大西洋18个产卵地点的607个人,包括两个温度线(5-12°C)和两个盐度线(5-35‰)。通过基因组扫描和景观遗传分析相结合,确定了四个遗传上不同的鲱鱼群:波罗的海,波罗的海-北海过渡区,北海/不列颠群岛和北大西洋;值得注意的是,对于中性和选定位点,样品表现出不同的聚类模式。我们发现统计上有力的证据表明,在全球范围内有16个离群位点存在差异选择,并且与9个位点的温度和盐度有显着相关性。在区域尺度上,我们确定了两个跨温度谱线具有平行模式的异常基因座,以及五个与北海/北大西洋的温度相关联的基因座。同样,我们发现了七个重复的离群值,其中五个与两个盐度谱系的低盐度显着相关。我们的结果揭示了异常基因座之间空间遗传变异的复杂模式,可能反映了对当地环境的适应。除了揭示高度易变物种的局部适应的精细规模外,我们的数据还强调了必须保护功能上重要的生物多样性。

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