Analysis of the genetic structure of the European eel Anguilla anguilla using the mtDNA D-loop region molecular marker

Sequence variation of the mtDNA D-loop region was analyzed in order to investigate the intraspecific evolution and the population genetic structure of the critically endangered European eel Anguilla anguilla. An additional attempt was made to collect information on the genetic characteristics of groups of eels representing naturally recruited eels to Lithuania and Latvia and introduced into Lithuanian lakes. A total of 148 eels were investigated, and 107 different haplotypes attributed to 39 haplogroups were determined during the study. A dataset comprising 229 sequences was created using the data from both this study and from earlier studies (n = 81). Analysis of this dataset revealed that haplotype diversity was 0.99567, the average number of nucleotide differences was 12.50544, there were 145 polymorphic sites and nucleotide diversity was 0.02426. No significant genetic differentiation was detected between different combinations of samples. However, the population genetic structure of this species could be characterized as a genetic mosaic formed due to the existence of reproductively isolated groups. The existence of a genetic mosaic in this species could be explained by the different evolutionary lineages found in the eel population.