Genetic Structure Among Breeding Herring Gulls (Larus argentatus) from the Great Lakes and Eastern Canada

Herring gulls (Larus argentatus) have been used as sentinel species for exposure to toxic chemicals since the 1960s. Reference populations in these studies have never been characterized to determine whether genetic differences might explain some of the effects seen in gulls at contaminated locations. Previously it was shown that there were higher rates of germline minisatellite DNA mutation rates in herring gulls colonizing sites located near steel industries in urban areas in the Great Lakes. It was suggested that population substructuring among gull colonies could account for differences in the mutation rates observed as a result of surveying different minisatellite loci. Here this explanation is dismissed by showing that genetic exchange among herring gull populations within the Great Lakes appears to be sufficient to ensure genetic homogeneity of these populations; in contrast, differences exist at the minisatellite loci scored between the gulls in the 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 genetic divergence from Maritime gulls should be investigated in more detail.