Journal of Fish Biology (2011) doi:10.1111/j.1095-8649.2011.02941.x, available online at wileyonlinelibrary.com BRIEF COMMUNICATION Low cytochrome b variation in bream Abramis brama B. Hayden*, I. Coscia† and S. Mariani‡§ *School of Biological Sciences, Queen’s University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, U.K., †Institute of Biological, Environmental and Rural Science (IBERS), Edward Llwyd Building, Aberystwyth University, Aberystwyth, Ceredigion SY23 2AD, U.K. and ‡School of Biology and Environmental Science, Science Centre West, University College Dublin, Dublin 4, Ireland (Received 16 July 2010, Accepted 7 February 2011) Variability in cytochrome b (cytb) in European populations of bream Abramis brama was assessed. The cytb gene was found to be strongly conserved in A. brama relative to other cyprinid taxa. This limits the usefulness of this marker in examining geographical genetic structure in this species and raises interesting questions as to the recent evolutionary history of the species. © 2011 The Authors Journal of Fish Biology © 2011 The Fisheries Society of the British Isles Key words: Cyprinidae; Eurasia; genetic variability; mitochondrial DNA; refugia. Bream Abramis brama (L. 1758) is an economically and recreationally important cyprinid species in many European countries (Lammens et al., 2002; Wolnomiejski & Grygiel, 2002). Although native to large parts of central and eastern Europe, its distribution has expanded significantly following human introductions (Kottelat & Freyhof, 2007). Abramis brama were not present in Italy prior to 1990 (Bianco, 1995) and have only recently been recorded in the Iberian peninsula (Kottelat & Freyhof, 2007). Similarly, though known to be native in Britain, A. brama was first reported in Ireland in the 1940s (Went, 1950); however, the date of its introduction to the island is thought to have occurred centuries earlier (Wheeler, 1977). The cytochrome b (cytb) gene has been a popular and effective tool in phylogeo- graphic studies of cyprinids (Kotlik & Berrebi, 2001; Mesquita et al., 2005; Ketmaier et al., 2008). A comparison of genetic diversity between recently introduced Irish A. brama populations and established continental populations was undertaken by comparing cytb sequences of Irish A. brama populations with native populations in Great Britain and mainland Europe. Populations of A. brama were collected using Norden gillnets (www.lundgrens fiske.com) from four locations in Ireland, including three river systems known to §Author to whom correspondence should be addressed. Tel.: +353 1716 2347; email: stefano.mariani@ ucd.ie 1 © 2011 The Authors Journal of Fish Biology © 2011 The Fisheries Society of the British Isles