New Danubian haplotype of brown trout (Salmo trutta L.) population from the Plitvica River revealed by mitochondrial DNA control region analysis

Brown trout (Salmo trutta L.) has a widespread distribution across Europe. It is characterized by a complex genetic structure and high genetic population differentiation throughout its distribution. Based on the sequence variation of the mitochondrial (mt) DNA control region, five major evolutionary lineages were proposed: Atlantic, Danubian, Adriatic, Mediterranean and marmoratus. However, some regions remain understudied and there is still a deficiency of data from particular areas of the brown trout native range. One such understudied area with importance to the evolutionary history of the species is Croatia. Individuals originating from the Plitvica River were investigated. In order to assess phylogenetic lineages affiliation, and address the question of autochthony of population in the river, mtDNA control region variations were analysed. Complete sequencing of the mtDNA control region revealed that all sampled individuals possess the same haplotype. Identified haplotype was a new, previously undescribed haplotype belonging to the Danubian lineage. Phylogenetic analysis with other Danubian haplotypes demonstrated that this new Danubian haplotype was most closely related to the Da9 haplotype. Thus, this novel haplotype has been named Da9a. It was concluded that brown trout population from the Plitvica River represent native population and should be protected from introduction of domesticated strains of brown trout.