Hoffman Joseph I, Chen Rebecca S, Vendrami David L J, Paijmans Anna J, Dasmahapatra Kanchon K, Forcada Jaume
Department of Animal Behavior, University of Bielefeld, P.O. BOX 100131, 33615 Bielefeld, Germany.
British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 OET, UK.
Genes (Basel). 2022 Mar 18;13(3):541. doi: 10.3390/genes13030541.
Much debate surrounds the importance of top-down and bottom-up effects in the Southern Ocean, where the harvesting of over two million whales in the mid twentieth century is thought to have produced a massive surplus of Antarctic krill. This excess of krill may have allowed populations of other predators, such as seals and penguins, to increase, a top-down hypothesis known as the 'krill surplus hypothesis'. However, a lack of pre-whaling population baselines has made it challenging to investigate historical changes in the abundance of the major krill predators in relation to whaling. Therefore, we used reduced representation sequencing and a coalescent-based maximum composite likelihood approach to reconstruct the recent demographic history of the Antarctic fur seal, a pinniped that was hunted to the brink of extinction by 18th and 19th century sealers. In line with the known history of this species, we found support for a demographic model that included a substantial reduction in population size around the time period of sealing. Furthermore, maximum likelihood estimates from this model suggest that the recovered, post-sealing population at South Georgia may have been around two times larger than the pre-sealing population. Our findings lend support to the krill surplus hypothesis and illustrate the potential of genomic approaches to shed light on long-standing questions in population biology.
关于南大洋自上而下和自下而上效应的重要性存在诸多争论，在20世纪中叶，超过200万头鲸鱼被捕杀，人们认为这导致南极磷虾大量过剩。这种磷虾过剩可能使海豹和企鹅等其他捕食者的数量增加，这是一种自上而下的假设，即“磷虾过剩假说”。然而，缺乏捕鲸前的种群基线使得研究主要磷虾捕食者数量与捕鲸相关的历史变化具有挑战性。因此，我们使用简化基因组测序和基于合并的最大复合似然方法来重建南极毛皮海狮的近期种群历史，南极毛皮海狮是一种鳍足类动物，在18和19世纪被海豹捕猎者捕杀至濒临灭绝。与该物种已知的历史一致，我们发现一个支持一种种群模型的证据，该模型包括在捕猎时期种群数量大幅减少。此外，该模型的最大似然估计表明，南乔治亚岛在捕猎后恢复的种群数量可能比捕猎前的种群数量大约多两倍。我们的研究结果支持了磷虾过剩假说，并说明了基因组方法在阐明种群生物学中长期存在的问题方面的潜力。
