Salvelinus alpinus haplotype abundance and diversity in arctic lakes and rivers@en

Sequence variation in the mtDNA control region of Arctic charr Salvelinus alpinus and Dolly Varden Salvelinus malma from 56 Siberian and North American populations was analysed to assess their phylogeographic relationships and the origins of sympatric forms. Phylogenetic trees confirm the integrity of phylogroups reported in previous mtDNA studies except that the Siberian group does not separate as a single cluster. Haplotype network analysis indicates the proximity of Siberian and Atlantic haplotypes. These are considered as one Eurasian group represented by the Atlantic, east Siberian (interior Siberia including Transbaikalia, Taimyr) and Eurosiberian (Finland, Spitsbergen, Taimyr) sub-groups. Salvelinus alpinus with presumably introgressed Bering group (malma) haplotypes were found along eastern Siberian coasts up to the Olenek Bay and the Lena Delta region, where they overlap with the Eurasian group and in the easternmost interior region. It is proposed that Siberia was colonized by S. alpinus in two stages: from the west by the Eurasian group and later from the east by the Bering group. The high diversity of Eurasian group haplotypes in Siberia indicates its earlier colonization by S. alpinus as compared with the European Alps. This colonization was rapid, proceeded from a diverse gene pool, and was followed by differential survival of ancestral mtDNA lineages in different basins and regions, and local mutational events in isolated populations. The results presented here support a northern origin of Transbaikalian S. alpinus, the dispersion of S. alpinus to the Lake Baikal Basin from the Lena Basin, segregation of S. alpinus between Lena tributaries and their restricted migration over the divides between sub-basins. These results also support sympatric origin of intralacustrine forms of S. alpinus.本研究对采自56个西伯利亚与北美种群的北极红点鲑（Salvelinus alpinus，英文名Arctic charr）及多尔伐红点鲑（Salvelinus malma，英文名Dolly Varden）的线粒体DNA（mtDNA）控制区序列变异开展分析，以评估二者的系统地理关系及同域形态的起源。系统发育树分析证实了此前mtDNA研究中报道的系统发育类群的完整性，仅西伯利亚类群未形成单一聚类簇。单倍型网络分析显示，西伯利亚单倍型与大西洋单倍型亲缘关系较近，二者被划归为同一欧亚类群，该类群包含大西洋亚类群、东西伯利亚亚类群（西伯利亚内陆区域，涵盖外贝加尔、泰梅尔地区）及欧亚西伯利亚亚类群（芬兰、斯匹次卑尔根、泰梅尔）。在西伯利亚东部沿海至奥列尼奥克湾与勒拿河三角洲区域，以及最东部的内陆区域，发现了携带疑似渐渗白令类群（malma）单倍型的北极红点鲑，该区域与欧亚类群的分布范围存在重叠。研究提出，西伯利亚地区的北极红点鲑存在两次殖民过程：欧亚类群从西部完成入侵，后续白令类群从东部完成殖民。相较于欧洲阿尔卑斯山地区，欧亚类群单倍型在西伯利亚的高多样性表明该类群更早完成对西伯利亚的殖民。此次殖民事件发生迅速，且源自多样化的基因库；随后，不同流域与区域的祖先mtDNA谱系发生了差异化存活，孤立种群中也出现了局部突变事件。本研究结果支持外贝加尔地区北极红点鲑的北方起源假说、北极红点鲑从勒拿河流域扩散至贝加尔湖流域的假说、勒拿河支流间北极红点鲑的种群分化，以及其在次级流域分水岭间的有限迁移。此外，本研究结果也支持北极红点鲑湖内同域形态的同域起源假说。