Speciation and genetic divergence of three species of charr from ancient Lake El'gygytgyn (Chukotka) and their phylogenetic relationships with other representatives of the genus Salvelinus

The diversity of phenotypically different and often reproductively isolated lacustrine forms of charrs of the genus Salvelinus represents a substantial problem for taxonomists and evolutionary biologists. Based on the analysis of variability of ten microsatellite loci and two fragments of mitochondrial DNA (control region and cyt-b gene), the evolutionary history of three charr species from Lake El'gygytgyn was reconstructed, and phylogenetic relationships between the main representatives of the genus were revealed. Three species from Lake El'gygytgyn were strongly reproductively isolated. Long-finned charr described previously as Salvethymus svetovidovi, an ancient endemic form in the lake, originated 3.5Mya (95% Bayesian credible intervals: 1.7, 6.1). Placement of this species in the phylogenetic tree of Salvelinus was not determined strictly, but it should be located in the basal part of the clade Salvelinus alpinus - S.malma species complex. The origin of small-mouth charr S.elgyticus and Boganida charr S.boganidae in Lake El'gygytgyn was related to allopatric speciation. Their ancestors were represented by two glacial lineages of Taranets charr S.alpinus taranetzi from Asia. In Lake El'gygytgyn, these lineages entered into secondary contact postglacially. A revision of the main phylogenetic groups within the Salvelinus alpinus - S.malma complex is conducted. The Boganida charrs from Lakes El'gygytgyn and Lama (Taimyr) belong to different phylogenetic groups of Arctic charr and should not be regarded as a single species S.boganidae. Using the charrs from Lakes El'gygytgyn and Lama as a case study, we show that a model of sympatric speciation, which seemed more probable based on previous empirical evidence, was rejected by other data.