Until recently, the dusky Canada goose (Branta canadensis occidentalis) was managed as one breeding population from the Copper River Delta (CRD), Alaska. Population numbers on the CRD have declined precipitously over the last three decades, due in part to changes in habitat. In 1981, a pair of Canada geese, presumably B.c. occidentalis, was reported nesting on Middleton Island (MID), in the Gulf of Alaska. Numbers of Canada geese on the island increased in the decade subsequent to a translocation of geese from CRD to MID, but it is unclear whether the increase is attributable to the translocation effort. We used genetic data derived from three classes of genetic markers to clarify relationships of Canada geese breeding in south-coastal Alaska. Geese were sampled from 5 populations: CRD, MID, Anchorage (ANC), Admiralty Island (ADM) in southeastern Alaska, and Green Island (GRN) in Prince William Sound (PWS). Mitochondrial DNA analyses demonstrate Canada geese from MID are nearly monomorphic for a unique haplotype fixed on GRN but not found in CRD or any other breeding population. Furthermore, nuclear markers consistently cluster MID with GRN to the exclusion of CRD. We suggest the current population on MID is not derived from birds translocated from CRD, but rather that MID was most likely colonised by birds inhabiting other island habitats within the PWS. Furthermore, since geese from the CRD share mtDNA haplotypes with geese from other breeding locales, they apparently share recent common ancestry and/or gene flow with populations representing other subspecies. Our genetic data raise questions about the validity of current management units of Canada geese.
Additional publication details
Molecular status of the dusky Canada goose (Branta canadensis occidentalis): A genetic assessment of a translocation effort