Genetic divergence and taxonomic status of chars of the genus Salvelinus

Abstract

The chars of the genus Salvelinus (Salmonidae) are characterized by high phenotypic diversity within lake or river basins, which creates some difficulties for determining the taxonomic (species) status of their forms and populations. The lack of the commonly accepted species concept complicates the situation. Based on the dominant biological species concept the reveal of the reproduction isolation of such forms or populations under conditions of sympatry can be the foundation for establishing the species status. The use of molecular genetic markers is a key approach to determining the degree of reproductive isolation and genetic divergence of populations. The paper compares and summarizes our and literary data on genetic studies of several species of the chars in the Russian Far East and northeast with regard to controversial issues of their species status. Using various molecular genetic markers, the validity of the species status of white char (S. albus) compared to the sympatric northern Dolly Varden (S. malma malma) was analyzed. The absence of the complete reproductive isolation between these chars makes it possible to consider S. albus as an ecotype or a form of S. m. malma, but not as a separate species. In pairs of sympatric S. m. malma-S. taranetzi and S. m. malma-S. levanidovi, the genetically well-expressed reproductive isolation was determined, which confirms their supposed status as separate species. The character of genetic differences for allozyme markers in the Asian allopatric population of S. m. malma and S. alpinus and the evidence of the reproductive isolation by microsatellite loci in sympatric Alaskan populations of these chars correspond to their status of separate species. The results of an analysis of mitochondrial genomes are evidence of their relatively recent divergence and possible hybridization between these species during their evolution. Significant genetic differences, including karyological differences between allopatric forms of northern and southern forms of Dolly Varden (S. m. malma-S. m. krascheninnikivi) correspond to the level of the species differentiation. However, the degree of their reproductive isolation in sympatry remains unknown. The data on mtDNA make it possible to suggest hybridization between these forms of Dolly Varden in their evolutionary past. The possibilities of using different molecular markers to identify the contemporary and historical isolation, and the evolution of contemporary char species and forms, which complicate the determination of their taxonomic status, are discussed.