Evolutionary distinctness of grayling {Thymallus thymallus) inhabiting the Adriatic river system, as based on mtDNA variation

The northern part of the peri-Adriatic river system is inhabited by a native grayling population. In comparison with the Danubian population most of the Adriatic population is regarded as morphologically distinct and therefore recognized as racially differentiated. DNA sequence analysis of the 394-bp fragment of the mtDNA control region and 363-bp fragment of the cytochrome b gene region from grayling specimens of the Adriatic, Danubian and Atlantic river systems revealed nine composite mtDNA haplotypes. The genetic divergence of the Adriatic and the Danubian-Atlantic haplotypes ranged from 2.52 to 3.10% and from 3.38 to 3.92% in the cytochrome b gene and control region, respectively. On the basis of sequence data an attempt was made to elucidate the phylogeography of the Adriatic population. The molecular data indicate an ancient monophyletic origin and also confirm its distinct position within the Thymallus thymallus species, in spite of the fact that stocking with the Danubian type occurred in the Adriatic river system. Therefore the Adriatic population deserves special attention. As a first step in its preservation, its formal distinction by using the name Adriatic grayling is proposed.