Skovrind Mikkel, Louis Marie, Westbury Michael V, Garilao Cristina, Kaschner Kristin, Castruita José Alfredo Samaniego, Gopalakrishnan Shyam, Knudsen Steen Wilhelm, Haile James S, Dalén Love, Meshchersky Ilya G, Shpak Olga V, Glazov Dmitry M, Rozhnov Viatcheslav V, Litovka Dennis I, Krasnova Vera V, Chernetsky Anton D, Bel'kovich Vsevolod M, Lydersen Christian, Kovacs Kit M, Heide-Jørgensen Mads Peter, Postma Lianne, Ferguson Steven H, Lorenzen Eline D
GLOBE Institute, University of Copenhagen, Denmark.
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany.
Mol Ecol. 2021 Jun;30(11):2543-2559. doi: 10.1111/mec.15915. Epub 2021 May 14.
Several Arctic marine mammal species are predicted to be negatively impacted by rapid sea ice loss associated with ongoing ocean warming. However, consequences for Arctic whales remain uncertain. To investigate how Arctic whales responded to past climatic fluctuations, we analysed 206 mitochondrial genomes from beluga whales (Delphinapterus leucas) sampled across their circumpolar range, and four nuclear genomes, covering both the Atlantic and the Pacific Arctic region. We found four well-differentiated mitochondrial lineages, which were established before the onset of the last glacial expansion ~110 thousand years ago. Our findings suggested these lineages diverged in allopatry, reflecting isolation of populations during glacial periods when the Arctic sea-shelf was covered by multiyear sea ice. Subsequent population expansion and secondary contact between the Atlantic and Pacific Oceans shaped the current geographic distribution of lineages, and may have facilitated mitochondrial introgression. Our demographic reconstructions based on both mitochondrial and nuclear genomes showed markedly lower population sizes during the Last Glacial Maximum (LGM) compared to the preceding Eemian and current Holocene interglacial periods. Habitat modelling similarly revealed less suitable habitat during the LGM (glacial) than at present (interglacial). Together, our findings suggested the association between climate, population size, and available habitat in belugas. Forecasts for year 2100 showed that beluga habitat will decrease and shift northwards as oceans continue to warm, putatively leading to population declines in some beluga populations. Finally, we identified vulnerable populations which, if extirpated as a consequence of ocean warming, will lead to a substantial decline of species-wide haplotype diversity.
预计几种北极海洋哺乳动物会受到与持续海洋变暖相关的海冰快速流失的负面影响。然而，北极鲸的影响仍不确定。为了研究北极鲸如何应对过去的气候波动，我们分析了从环北极范围内采样的206个白鲸（白鲸属）线粒体基因组以及四个核基因组，涵盖了大西洋和太平洋北极地区。我们发现了四个分化良好的线粒体谱系，它们在约11万年前最后一次冰川扩张开始之前就已形成。我们的研究结果表明，这些谱系在异域中分化，反映了冰川期北极海架被多年海冰覆盖时种群的隔离。随后的种群扩张以及大西洋和太平洋之间的二次接触塑造了当前谱系的地理分布，并可能促进了线粒体基因渗入。我们基于线粒体和核基因组的种群动态重建显示，与之前的埃姆期和当前的全新世间冰期相比，末次盛冰期（LGM）期间的种群规模明显较小。栖息地建模同样显示，末次盛冰期（冰川期）的适宜栖息地比现在（间冰期）少。综合来看，我们的研究结果表明了白鲸的气候、种群规模和可用栖息地之间的关联。对2100年的预测表明，随着海洋持续变暖，白鲸的栖息地将减少并向北转移，推测这将导致一些白鲸种群数量下降。最后，我们确定了一些易危种群，如果这些种群因海洋变暖而灭绝，将导致全物种单倍型多样性大幅下降。
