Population structure of Purple Sandpipers (Calidris maritima) as revealed by mitochondrial DNA and microsatellites

The Purple Sandpiper (Calidris maritima) is a medium-sized shorebird that breeds in the Arctic and winters along northern Atlantic coastlines. Migration routes and affiliations between breeding grounds and wintering grounds are incompletely understood. Some populations appear to be declining, and future management policies for this species will benefit from understanding their migration patterns. This study used two mitochondrial DNA markers and 10 microsatellite loci to analyze current population structure and historical demographic trends. Samples were obtained from breeding locations in Nunavut (Canada), Iceland, and Svalbard (Norway) and from wintering locations along the coast of Maine (USA), Nova Scotia, New Brunswick, and Newfoundland (Canada), and Scotland (UK). Mitochondrial haplotypes displayed low genetic diversity, and a shallow phylogeny indicating recent divergence. With the exception of the two Canadian breeding populations from Nunavut, there was significant genetic differentiation among samples from all breeding locations; however, none of the breeding populations was a monophyletic group. We also found differentiation between both Iceland and Svalbard breeding populations and North American wintering populations. This pattern of divergence is consistent with a previously proposed migratory pathway between Canadian breeding locations and wintering grounds in the United Kingdom, but argues against migration between breeding grounds in Iceland and Svalbard and wintering grounds in North America. Breeding birds from Svalbard also showed a genetic signature intermediate between Canadian breeders and Icelandic breeders. Our results extend current knowledge of Purple Sandpiper population genetic structure and present new information regarding migration routes to wintering grounds in North America.