Genetic differentiation among Danish brown trout (Salmo trutta L. ) populations, as detected by RFLP analysis of PCR amplified mitochondrial DNA segments

An initial screening with 18 restriction endonucleases of brown trout mitochondrial DNA from three regions of Denmark revealed no variation in the D-loop while seven restriction endonucleases were found to detect variability in the NADH-dehydrogenase 1 and/or 5/6 regions. Thirteen different haplotypes were observed, fewer in the Lake Hald populations than in the other samples, probably a result of nonexisting gene flow due to an impassable dam.

No correlation was found between geography and the genetic relationships among haplotypes. Significant genetic differentiation was observed among the three main regions. Genetic differentiation among populations was much more pronounced in the Lake Hald than in the Bornholm region. The genetic relationships among populations of the Lake Hald region suggested by mtDNA data were not in accordance with allozyme data and the known history of the populations, while estimates of genetic differentiation and gene flow inferred by the two methods were in agreement.