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


RESULTS
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.


CONCLUSIONS
The success of roach x 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.
UCD School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland. brian.hayden@ucd.ie
Brian
B
Hayden
Domitilla
D
Pulcini
Mary
M
Kelly-Quinn
Martin
M
O'Grady
Joe
J
Caffrey
Aisling
A
McGrath
Stefano
S
Mariani
D000818:Animals; D003530:Cyprinidae / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics* / Q000254:growth & development; D004272:DNA, Mitochondrial / Q000235:genetics; D017753:Ecosystem; D005260:Female; D005828:Genetics, Population; D006824:Hybridization, Genetic; D007494:Ireland; D008297:Male; D017422:Sequence Analysis, DNA
D004272:DNA, Mitochondrial