Salvelinus alpinus haplotype abundance and diversity in arctic lakes and rivers

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.本研究对来自56个西伯利亚和北美种群的北极红点鲑（Salvelinus alpinus）与花北极鲑（Salvelinus malma）的线粒体DNA（mtDNA）控制区序列变异进行分析，以评估其系统地理学关系及同域型的起源。系统发育树证实了此前线粒体DNA研究中报道的支群完整性，仅西伯利亚支群未形成单一聚类簇。单倍型网络分析表明西伯利亚单倍型与大西洋单倍型亲缘关系较近。上述两类单倍型被归为一个欧亚支群，其下包含大西洋、东西伯利亚（西伯利亚内陆地区，包括外贝加尔、泰梅尔）以及欧亚西伯利亚（芬兰、斯匹次卑尔根、泰梅尔）三个亚支群。在西伯利亚东部沿海直至奥列涅克湾与勒拿三角洲区域，以及最东部的内陆区域，均发现携带有疑似渐渗自白令支群（即花北极鲑）单倍型的北极红点鲑，这些区域同时存在欧亚支群的个体。研究推测，北极红点鲑对西伯利亚的定殖分为两个阶段：欧亚支群从西部侵入，随后白令支群从东部侵入。与欧洲阿尔卑斯山区域相比，西伯利亚地区欧亚支群单倍型的高多样性，表明北极红点鲑更早完成了对该区域的定殖。此次定殖过程快速且源自一个多样的基因库，随后不同流域与区域的祖先线粒体DNA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起源于北部，支持北极红点鲑从勒拿盆地扩散至贝加尔湖流域，以及勒拿河支流间北极红点鲑的种群分化和它们在亚流域间的受限迁移。上述结果同时支持北极红点鲑湖内种群的同域起源假说。