GENETIC DIFFERENTIATION AMONG DANISH BROWN TROUT 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 dete ct variability in the NADH-dehydrogenase 1 and/or 5/6 regions. Thirtee n different haplotypes were observed, fewer in the Lake Hald populatio ns than in the other samples, probably a result of nonexisting gene fl ow due to an impassable dam, No correlation was found between geograph y and the genetic relationships among haplotypes. Significant genetic differentiation was observed among the three main regions. Genetic dif ferentiation among populations was much more pronounced in the Lake Ha ld than in the Bornholm region. The genetic relationships among popula tions of the Lake Hald region suggested by mtDNA data were not in acco rdance with allozyme data and the known history of the populations, wh ile estimates of genetic differentiation and gene flow inferred by the two methods were in agreement. (C) 1996 The Fisheries Society of the British Isles