论文标题：Hybridization between two high Arctic cetaceans confirmed by genomic analysis

期刊：Scientific Reports

作者：Mikkel Skovrind, Jose Alfredo Samaniego Castruita, James Haile, Eve C. Treadaway, Shyam Gopalakrishnan, Michael V. Westbury, Mads Peter Heide-Jørgensen, Paul Szpak, Eline D. Lorenzen

发表时间：2019/06/20

数字识别码： 10.1038/s41598-019-44038-0

原文链接：http://t.cn/AipA1xJB

研究人员对1990年在西格陵兰发现的一块颅骨进行了基因分析，发现它属于一头雌性独角鲸和一头雄性白鲸的第一代雄性杂交后代。这一发现代表了独角鲸与白鲸可能进行过杂交的唯一已知的证据。

图1：白鲸（a）和独角鲸（b）的分布范围，和（c）本研究中白鲸（蓝）和独角鲸（绿）取样地点图源：Skovrind等

上述颅骨存于丹麦自然历史博物馆，丹麦哥本哈根大学的Mikkel Skovrind、Eline Lorenzen及同事对从该样本牙齿中提取的基因组DNA进行了分析，并将其与8头活体白鲸和8头活体独角鲸的DNA进行对比，这些鲸鱼来自与上述颅骨发现地一样的区域。分析表明，颅骨样本54%属于白鲸，46%属于独角鲸。作者使用X染色体数量和常染色体数量之比（一种常见的判断个体性别的方法），推断出白鲸-独角鲸的杂交后代为雄性。线粒体基因组（只通过母系遗传的一小部分DNA）分析表明，该杂交后代的母亲为独角鲸。

图2：根据间日疟原虫标本线粒体谱系绘制的贝叶斯系统发生树（A）和中间连接网络（B）

作者还分析了颅骨样本骨胶原所含的碳氮同位素，并将其与18头独角鲸和18头白鲸颅骨的骨胶原做参照对比。杂交种颅骨样本的碳同位素浓度高于其它参照颅骨的，这表明杂交种的食性不同于独角鲸或白鲸。作者据此推断，杂交种觅食的位置比独角鲸或白鲸更接近海底（底栖带）。

摘要：In 1990, a skull from a morphologically unusual Monodontid was found in West Greenland and collected for the Natural History Museum of Denmark, University of Copenhagen. From its intermediate morphology, the skull was hypothesized to be a beluga/narwhal hybrid. If confirmed, the specimen would, to our knowledge, represent the sole evidence of hybridization between the only two toothed whale species endemic to the Arctic. Here we present genome-wide DNA sequence data from the specimen and investigate its origin using a genomic reference panel of eight belugas and eight narwhals. Our analyses reveal that the specimen is a male, first-generation hybrid between a female narwhal and a male beluga. We use stable carbon and nitrogen isotope analysis to investigate the dietary niche of the hybrid and find a higher δ13C value than in both belugas and narwhals, suggesting a foraging strategy unlike either parental species. These results further our understanding of the interaction between belugas and narwhals, and underscore the importance of natural history collections in monitoring changes in biodiversity. In addition, our study exemplifies how recent major advances in population genomic analyses using genotype likelihoods can provide key biological and ecological insights from low-coverage data (down to 0.05x).

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期刊介绍：Scientific Reports (https://www.nature.com/srep/) is an online, open access journal from the publishers of Nature. We publish scientifically valid primary research from all areas of the natural and clinical sciences.

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（来源：科学网）