Genetic structure among breeding herring gulls (Larus argentatus) from theGreat Lakes and Eastern Canada

Herring gulls (Larus argentatus) have been used as sentinel species for exp osure to toxic chemicals since the 1960s. Reference populations in these st udies have never been characterised to determine whether generic difference s might explain some of the effects seen in gulls at contaminated locations . Previously it was shown that there were higher rates of germline minisate llite DNA mutation rates in herring gulls colonizing sites located near ste el industries in urban areas iii the Great Lakes. It was suggested that pop ulation substructuring among gull colonies could account for the difference s in the mutation rates observed as a result of surveying different minisat ellite loci. Here this explanation is dismissed by showing that genetic exc hange among her ring gull populations within the Great Lakes appears to be sufficient to ensure generic homogeneity of these populations, in contrast, differences exist at the minisatellite loci scored between the gulls in th e Great Lakes and the Maritimes. It is suggested that reference samples for future Great Lakes herring gull studies be selected from within the Great Lakes, and that potential generic divergence from Maritime grills should be investigated in more detail.