Introgressive hybridization between two phylogenetic lineages of charrs ( Salvelinus : Salmonidae) in northeastern Asia

Abstract

Many lacustrine charrs of the genus Salvelinus were described as separate species, and their origin and phylogenetic relationships are still under debate. In this study, we described the genetic variation of charrs from Lake Grand (Elikchan Lake Group, the mainland coast of the Sea of Okhotsk, Russia) and several locations outside of this system based on eight microsatellite (ms) loci and mitochondrial (mt) DNA control region. We tested the hypothesis of the resident charr membership to (a) the Arctic lineage of Salvelinus taranetzi sensu (Oleinik et al., Russian Journal of Genetics, 51, 2015, 55); (b) the Bering lineage of the Northern Dolly Varden Salvelinus malma malma; and (c) the Atlantic lineage of the Arctic charr Salvelinus alpinus. Analysis of phylogenetic relationships based on the mtDNA control region showed that all individuals from Lake Grand grouped with the Bering lineage. Bayesian analysis using msDNA supports the clustering together of charrs from Lake Grand and Arctic lineage, regardless of their mtDNA haplotypes. Incongruence between mtDNA and msDNA markers provided strong evidence of historical mtDNA introgression from S. malma malma to S. taranetzi. Patterns of divergence confirm a postglacial secondary contact of the representatives of Arctic and Bering lineages in the area of the Sea of Okhotsk coast and past hybridization in Lake Grand with the following features: (a) complete fixation of introgressed mtDNA of one species within populations of another and (b) absence of modern population of S. malma malma in the lake.

Salmonidae Genome: Features, Evolutionary and Phylogenetic Characteristics

“…Longer DNA sequences have previously been proven to give an acceptable resolution of relatively high connections in fish [ 317 ]. A study by Oleinik et al (2021) additionally showed that mitogenomes could make up a reliable phylogenetic tree and resolve relationships between closely related species of loaches [ 318 ]. On the basis of morphological similarity, the boganids of Chukotka and Taimyr were attributed to the same species [ 286 , 306 ].…”

“…An earlier study showed S. alpinus individuals with introgressed haplotypes from the Bering clade of S. malma along the eastern coast of Siberia to be parapatric [ 171 ]. In a very recent study, mtDNA introgression from S. malma malma to S. taranetzi near the Sea of Okhotsk, due to which representatives of the first species did not remain in this location completely [ 318 ]. In addition, postglacial hybridization between different glacial lineages of S. alpinus has been demonstrated to survive in separate refugia [ 170 ].…”