Fisheries and Oceans Canada, Northwest Atlantic Fisheries Centre, St. John's, NL, A1C 5X1, Canada.
Fisheries and Oceans Canada, Bedford Institute of Oceanography, Dartmouth, NS, B2Y 4A2, Canada.
Heredity (Edinb). 2019 Jan;122(1):69-80. doi: 10.1038/s41437-018-0087-9. Epub 2018 May 17.
In the northwest Atlantic Ocean, sea scallop (Placopecten magellanicus) has been characterized by a latitudinal genetic cline with a breakpoint between northern and southern genetic clusters occurring at 45°N along eastern Nova Scotia, Canada. Using 96 diagnostic single-nucleotide polymorphisms (SNPs) capable of discriminating between northern and southern clusters, we examined fine-scale genetic structure of scallops among 27 sample locations, spanning the largest geographic range evaluated in this species to date (37-51°N). Here, we confirmed previous observations of northern and southern groups, but we show that the boundary between northern and southern clusters is not a discrete latitudinal break. Instead, at latitudes near the previously described boundary, we found unexpected patterns of fine-scale genetic structure occurring between inshore and offshore sites. Scallops from offshore sites, including St. Pierre Bank and the eastern Scotian Shelf, clustered with southern stocks, whereas inshore sites at similar latitudes clustered with northern stocks. Our analyses revealed significant genetic divergence across small spatial scales (i.e., 129-221 km distances), and that spatial structure over large and fine scales was strongly associated with temperature during seasonal periods of thermal minima. Clear temperature differences between inshore and offshore locations may explain the fine-scale structuring observed, such as why southern lineages of scallop occur at higher latitudes in deeper, warmer offshore waters. Our study supports growing evidence that fine-scale population structure in marine species is common, often environmentally associated, and that consideration of environmental and genomic data can significantly enhance the identification of marine diversity and management units.
在北大西洋西北部，扇贝（Placopecten magellanicus）的遗传结构呈纬度梯度变化，在加拿大新斯科舍省东部45°N 处，存在一个南北遗传群的断点。本研究使用 96 个可区分南北群的诊断单核苷酸多态性（SNP），检测了 27 个采样点扇贝的精细遗传结构，这些采样点的地理分布范围在该物种中是迄今为止最大的（37-51°N）。本研究证实了先前关于南北群的观察结果，但表明南北群的边界不是离散的纬度断裂。相反，在接近先前描述的边界的纬度上，我们发现了近海和外海地点之间存在意想不到的精细遗传结构模式。来自外海地点的扇贝，包括圣皮埃尔浅滩和东部斯科舍浅滩，与南部种群聚类，而类似纬度的近岸地点则与北部种群聚类。我们的分析表明，在小的空间尺度上（即 129-221km 距离）存在显著的遗传差异，并且在大尺度和小尺度上的空间结构与季节性热最小值期间的温度强烈相关。近岸和外海地点之间明显的温度差异可能解释了所观察到的精细结构，例如为什么扇贝的南部谱系出现在更深、更温暖的外海水域的较高纬度。本研究支持越来越多的证据表明，海洋物种的精细种群结构很常见，通常与环境有关，并且考虑环境和基因组数据可以显著提高海洋多样性和管理单元的识别能力。
