Home > Research > Trumpeter Swan
POPULATION DIFFERENTIATION - Trumpeter Swan
Funding Partners:
US Fish and Wildlife Service
Related Publications:
Oyler-McCance, S.J., F. A. Ransler, L. K. Berkman and T. W. Quinn. 2007 A Rangewide Population Genetic Study of Trumpeter Swans.Conservation Genetics 8: 1339-1353.
St John J., F.A. Ransler, T.W. Quinn, and S.J. Oyler-McCance. 2006. Characterization of microsatellite loci isolated in trumpeter swan (Cygnus buccinator). Molecular Ecology Notes 6:1083-1085
Summary:
Using DNA sequence and microsatellite analyses, we are
investigating whether or
not the tri-state flock of the Rocky Mountain population of Trumpeter
Swans (Cygnus buccinator) is genetically different from other flocks
across the swan's range. Additionally, we will be documenting gene flow
and genetic diversity among flocks and populations. We are also collecting
baseline genetic data from restoration flocks in an attempt to provide
better genetic information for continuing restoration efforts.
Historically, trumpeter swans were abundant throughout most of North America. Habitat destruction and over-harvest led to the significant reduction of the species. In the coterminous U.S., only 1 group of trumpeter swans survived overexploitation (in Montana, Idaho, and Wyoming [i.e., the Tri-state region]) near what is now Red Rock Lakes, NWR. Until the mid-1900s, these birds (subsequently termed 'Tri-state' birds) were believed to be the only remaining free-ranging trumpeters. Following the discovery of the additional birds and assessment of band-recovery information, the swans were delineated into populations largely along administrative boundaries. The Pacific Population (PP) is comprised of birds nesting primarily in Alaska and western portions of the Yukon Territory and British Columbia. The Rocky Mountain Population (RMP) consists of birds comprising 2 flocks, the Tri-state birds mentioned above and another group nesting in the Grande Prairie-Peace River region of Alberta.
Additionally,
attempts to restore nesting trumpeters to formerly occupied range have
occurred since the late 1930s. Translocations of birds and eggs from the
RMP resulted in the establishment of nesting flocks at Ruby Lake, Nevada
and Malheur NWR in Oregon. Those flocks currently are included in the
RMP for management purposes. Restoration efforts also resulted in the
establishment of the Interior Population (IP), which is comprised of two
major groups. Birds inhabiting the Midwest were derived primarily from
the translocation of swan eggs from AK (PP). In contrast, the High Plains
flock of the IP was established by translocating primarily Tri-state (RMP)
birds and eggs to South Dakota. Wintering swans also have been translocated
from the Tri-state area (RMP) to UT, OR, WY, and areas of ID outside the
Tri-state region in an attempt to establish migratory routes for the Tri-state
flock and to relieve pressure on that habitat that has become saturated
by RMP swans migrating south from Alberta. Despite terming these different
populations, the distinctions are based largely on political boundaries
and may not represent biological differences among groups.
Much controversy surrounds the management of the RMP. Although the 2 flocks comprising this population are spatially disjunct during the nesting season, they are sympatric during winter in the Tri-state region. The population as a whole has been increasing (6% per year) since 1975. However, most of the growth has occurred in the Canadian flock; the size of the Tri-state flock has remained low. The existence or extent of genetic interchange between these 2 groups remains unknown, yet may influence management practices and whether the flocks should be managed in the aggregate or as 2 distinct entities. Further, the amount of genetic distinctness among trumpeter swans rangewide is an important parameter to understand given the increasingly complex level and patterns of restoration efforts that often involve translocations of swans and of swan eggs. The distribution of genetic variation among populations across the range remains unclear. The objective of this study is to assess the genetic differences among some of the different sample locales to determine if their treatment as discrete biological populations is valid. Additional information that may be derived from this genetic data, if populations are genetically distinct, is: (1) study migration patterns and routes, and (2) identify the breeding-ground origin of birds sampled on migration or wintering areas.
