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Hybridisation between two cyprinid fishes in a novel habitat: genetics, morphology and life-history traits

Brian Hayden1*, Domitilla Pulcini2, Mary Kelly-Quinn1, Martin O'Grady3, Joe Caffrey3, Aisling McGrath1 and Stefano Mariani1*

Author Affiliations

1 UCD School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland

2 Laboratory of Experimental Ecology and Aquaculture, Department of Biology, University of Rome 'Tor Vergata', Via della Ricerca Scientifica s.n.c, 00133 Rome, Italy

3 Central Fisheries Board, Swords Business Campus, Swords, Co. Dublin, Ireland

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BMC Evolutionary Biology 2010, 10:169  doi:10.1186/1471-2148-10-169

Published: 8 June 2010



The potential role hybridisation in adaptive radiation and the evolution of new lineages has received much recent attention. Hybridisation between roach (Rutilus rutilus L.) and bream (Abramis brama L.) is well documented throughout Europe, however hybrids in Ireland occur at an unprecedented frequency, often exceeding that of both parental species. Utilising an integrated approach, which incorporates geometric morphometrics, life history and molecular genetic analyses we identify the levels and processes of hybridisation present, while also determining the direction of hybridisation, through the analysis of mitochondrial DNA.


The presence of F2 hybrids was found to be unlikely from the studied populations, although significant levels of backcrossing, involving both parental taxa was observed in some lakes. Hybridisation represents a viable conduit for introgression of genes between roach and bream. The vast majority of hybrids in all populations studied exhibited bream mitochondrial DNA, indicating that bream are maternal in the majority of crosses.


The success of roach × bream hybrids in Ireland is not due to a successful self reproducing lineage. The potential causes of widespread hybridisation between both species, along with the considerations regarding the role of hybridisation in evolution and conservation, are also discussed.