Crossing the divide: admixture across the Antarctic Polar Front revealed by the brittle star Astrotoma agassizii

The Antarctic Polar Front (APF) is one of the most well-defined and persistent oceanographic features on the planet and serves as a barrier to dispersal between the Southern Ocean and lower latitudes. High levels of endemism in the Southern Ocean have been attributed to this barrier, whereas the accompanying Antarctic Circumpolar Current (ACC) likely promotes west-to-east dispersal. Previous phylogeographic work on the brittle star Astrotoma agassizii Lyman, 1875 based on mitochondrial genes suggested isolation across the APF, even though populations in both South American waters and the Southern Ocean are morphologically indistinguishable. Here, we revisit this finding using a high-resolution 2b-RAD (restriction-site-associated DNA) single-nucleotide polymorphism (SNP)-based approach, in addition to enlarged mitochondrial DNA data sets (16S rDNA, COI, and COII), for comparison to previous work. In total, 955 biallelic SNP loci confirmed the existence of strongly divergent populations o...

南极极锋（Antarctic Polar Front, APF）是全球特征最为明确且持续稳定的海洋学特征之一，同时作为分隔南大洋与低纬度海域的物种扩散屏障。南大洋高度发达的特有物种现象被归因于该屏障的阻隔作用，而与之相伴的南极绕极流（Antarctic Circumpolar Current, ACC）则大概率促进了西向东的物种扩散。此前针对阿加西兹海蛇尾（Astrotoma agassizii Lyman, 1875）开展的系统地理学研究以线粒体基因为分子标记，结果显示南极极锋两侧的种群存在遗传隔离——尽管南美洲海域与南大洋的该物种种群在形态上并无二致。本研究采用高分辨率2b-RAD（限制性酶切位点相关DNA，restriction-site-associated DNA）单核苷酸多态性（single-nucleotide polymorphism, SNP）分析方法，并结合扩增后的线粒体DNA数据集（涵盖16S rDNA、COI及COII基因），对此前的研究结论进行重新验证与对比分析。本研究共获得955个双等位基因单核苷酸多态性位点，结果证实了显著分化种群的存在……