Population genetic differentiation and hybridization in the Glaucous Gull (Larus hyperboreus)

Abstract

Climate change poses a significant threat to the future of Arctic ecosystems. To effectively conserve Arctic species, genetically differentiated populations must be defined for adaptive and neutral genetic variation to be appropriately managed. This project examines population genetic differentiation in the Glaucous Gull (Larus hyperboreus) – a circumpolar Arctic species – and assesses hybridization between Glaucous Gulls and three closely-related species. The Glaucous Gull is a valuable species, biologically and culturally. As apex predators, Glaucous Gulls develop high levels of toxins in their tissue and are, therefore, excellent bioindicators of the long-range transport of contaminants in the Arctic. Glaucous Gulls also hybridize with other white-headed gull species where breeding ranges overlap. Although the International Union for Conservation of Nature currently lists Glaucous Gull as Least Concern, declines have been reported across their range in Arctic Canada. Currently no fine­scale population genetic information exists for this species, and management units have not been delineated. Double digest restriction-site associated DNA sequencing was conducted on 62 Glaucous Gulls, 18 American Herring Gulls (L. smithsonianus), 6 European Herring Gulls (L. argentatus), and 15 Glaucous-winged Gulls (L. glaucescens) sampled across the North American and European Arctic. Despite the geographic distance between sampling locations, molecular assignments and principal coordinates analysis suggest only weak population differentiation between sampled European and Canadian colonies of Glaucous Gull. Interspecific analyses using 2145 loci show that Glaucous Gull and Glaucous-winged Gull are genetically distinct species but that Glaucous Gull and the two species of Herring Gull are only weakly differentiated. Several sampled individuals may represent hybrids between Glaucous Gulls and American Herring Gulls. Detailed information on population genetic structure and hybridization will help conservation practitioners effectively manage the long-term persistence of Glaucous Gull populations. Proactive management strategies for this species will benefit both Glaucous Gull and the entire Arctic ecosystem.