Complete Mitochondrial Genomes of Endemic Charrs of Salvelinus: Implications for Taxonomy and Species Identification

Gene fragments on which databases usually rely are not always suited for identification of endemic species of disputable origin. Clarification of the unresolved issues requires more comprehensive mitochondrial genome-based phylogenetics to enhance understanding of the relationship and delineation of species as a basis for their conservation. This study focuses on endemic charrs (Salvelinus, Salmonidae). The complete mitochondrial genomes (mitogenomes) of Longhead charr Salvelinus kronocius and Schmidt's charr Salvelinus schmidti from Lake Kronotskoye (Kamchatka Peninsula, Russia) were sequenced and compared with the mitogenomes of a putative ancestor species, Northern Dolly Varden Salvelinus malma malma. We analysed 36 mitogenomes, including six ones sequenced in this study, 26 charr sequences published in GenBank, and four outgroup sequences. We obtained additional evidence that the lacustrine charrs belong to the Beringian lineage with very low level of mitogenome divergence. Our findings demonstrate that the mitogenome sequencing serves as a valuable tool in clarifying the taxonomic status of narrow-range endemics or rare charrs and may be useful for future genetic investigations of charrs and other groups with high level of diversity toward proper assessment of the status of the controversial taxa. Expanding genetic resources is necessary for species identification and biodiversity monitoring, as well as for conservation measures aimed at controlling adverse natural and anthoropogenic impacts on fish population systems.