ORIGINAL PAPER A rangewide population genetic study of trumpeter swans

Abstract For management purposes, the range of naturally occurring trumpeter swans (Cygnus buccina-tor) has been divided into two populations, the Pacific Coast Population (PP) and the Rocky Mountain Pop-ulation (RMP). Little is known about the distribution of genetic variation across the species ’ range despite increasing pressure to make difficult management decisions regarding the two populations and flocks within them. To address this issue, we used rapidly evolving genetic markers (mitochondrial DNA sequence and 17 nuclear microsatellite loci) to eluci-date the underlying genetic structure of the species. Data from both markers revealed a significant differ-ence between the PP and RMP with the Yukon Terri-tory as a likely area of overlap. Additionally, we found that the two populations have somewhat similar levels of genetic diversity (PP is slightly higher) suggesting that the PP underwent a population bottleneck similar to a well-documented one in the RMP. Both genetic structure and diversity results reveal that the Tri-State flock, a suspected unique, non-migratory flock, is not genetically different from the Canadian flock of the RMP and need not be treated as a unique population from a genetic standpoint. Finally, trumpeter swans appear to have much lower mitochondrial DNA variability than other waterfowl studied thus far which may suggest a previous, species-wide bottleneck