A molecular approach to detect hybridization between bream Abramis brama, roach Rutlius rutilus and rudd Scardinius erythrophthalmus

Hybridization between roach Rutilus rutilus, bream Abramis brama and rudd Scardinius erythrophthalmus was investigated using morphological and genetic analysis employing both nuclear (ITS1) and mitochondrial (cytochrome b) markers. Allele-specific amplification (ASA) reactions for both markers were developed and ITSI sequence data for all three species are presented. Sequencing detected two ITSI haplotypes within both roach and bream which most likely evolved in isolation and were subsequently brought together as a result of restocking by anglers. Analysis of cloned hybrid nuclear ribosomal DNA revealed evidence of recombination between parental ITSI sequences. ASA proved to be an effective method for identifying hybrids and detected multiple ITSI copies in fishes identified as purebred by morphological analysis. In addition this suggests post-F1 hybridization and introgression may be occurring between roach and bream, and rudd and bream, although some barriers appear to be suppressing backcrosses within the hybrid population. Analysis of the hybrid population demonstrated that hybridization has occurred in both directions. (c) 2006 The Fisheries Society of the British Isles.