Ancient DNA (aDNA) approaches have been successfully used to infer the long-term impacts of climate change, domestication, and human exploitation in a range of terrestrial species. Nonetheless, studies investigating such impacts using aDNA in marine species are rare. Atlantic cod (Gadus morhua), is an economically important species that has experienced dramatic census population declines during the last century. Here, we investigated 48 ancient mitogenomes from historical specimens obtained from a range of archaeological excavations in northern Europe dated up to 6500 BCE. We compare these mitogenomes to those of 496 modern conspecifics sampled across the North Atlantic Ocean and adjacent seas. Our results confirm earlier observations of high levels of mitogenomic variation and a lack of mutation-drift equilibrium – suggestive of population expansion. Furthermore, our temporal comparison yields no evidence of measurable mitogenomic changes through time. Instead, our results indicate that mitogenomic variation in Atlantic cod reflects past demographic processes driven by major historical events (such as oscillations in sea level) and subsequent gene flow rather than contemporary fluctuations in stock abundance. Our results indicate that historical and contemporaneous anthropogenic pressures such as commercial fisheries have had little impact on mitogenomic diversity in a wide-spread marine species with high gene flow such as Atlantic cod. These observations do not contradict evidence that overfishing has had negative consequences for the abundance of Atlantic cod and the importance of genetic variation in implementing conservation strategies. Instead, these observations imply that any measures towards the demographic recovery of Atlantic cod in the eastern Atlantic, will not be constrained by recent loss of historical mitogenomic variation.

中文翻译：

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历史人口统计过程决定了古代大西洋鳕鱼有丝分裂基因组的遗传变异

古代DNA（aDNA）方法已成功用于推断气候变化，驯化和人类对一系列陆地物种的剥削的长期影响。但是，很少有人使用aDNA研究这类影响在海洋物​​种中的研究。大西洋鳕（Gadus morhua）是一种重要的经济物种，上个世纪人口普查人口急剧减少。在这里，我们从历史标本中调查了48个古代有丝分裂基因组，这些标本是从北欧可追溯到公元前6500年的一系列考古发掘中获得的。我们将这些有丝分裂基因组与在北大西洋和邻近海域采样的496种现代同种菌种进行了比较。我们的研究结果证实了早期关于线粒体基因组变异的高水平观察和缺乏突变漂移平衡的现象，这提示了种群的扩大。此外，我们的时间比较没有证据表明随着时间的推移可测量的线粒体基因组变化。相反，我们的结果表明，大西洋鳕鱼的线粒体基因组变化反映了主要历史事件（例如海平面的振荡）和随后的基因流（而不是当代种群数量的波动）驱动的过去的人口统计学过程。我们的结果表明，历史和同时代的人为压力（例如商业性渔业）对具有高基因流量的广泛海洋物种（如大西洋鳕鱼）的线粒体基因组多样性影响很小。这些观察结果与证据表明过度捕捞对大西洋鳕鱼的丰富和遗传变异在实施保护战略中的重要性产生了负面影响。取而代之的是，这些观察结果表明，针对大西洋鳕鱼在东大西洋的人口统计学恢复采取的任何措施都不会受到近期线粒体基因组历史变异的丧失的限制。