Conservation genetics of high-arctic Gull species at risk: II. Diversity in the mtDNA control region of Threatened Ross's Gull (Rhodostethia rosea).

Ross's Gull (Rhodostethia rosea) is the rarest of Canadian high-arctic gulls, and is listed as Threatened under Canada's Species-At-Risk Act. The large majority of birds breed in Siberia: the origins and affinities of four extremely small breeding colonies observed since 1978 in the Canadian high arctic are unknown. We compared a 515-bp region of the mtDNA Control Region amplified from material in museum collections taken from non-breeding birds in Canada (n = 8) and Alaska (n = 6), the latter passage migrants from the Siberian populations. The Alaskan birds all have distinct haplotypes that differ by as many as six SNPs: Canadian birds taken in the vicinity of the breeding colonies show only two of these. We hypothesize the origins of the Canadian breeding colonies as recent founder events by small numbers of passage migrants from Siberia via Alaska. Ross's Gull maintains a very tenuous breeding presence in the Canadian high Arctic.