Genetics Show Current Decline and Pleistocene Expansion in Northern Spotted Owls

Open-File Report 2008-1239
By: , and 



The northern spotted owl (Strix occidentalis caurina) is one of the most controversial threatened subspecies ever listed under the U.S. Endangered Species Act. Because of concern for persistence of the subspecies, logging on Federal lands in the U.S. Pacific Northwest was dramatically reduced under the Northwest Forest Plan in 1994. Despite protection of its remaining forest habitat, recent field studies show continued demographic declines of northern spotted owls. One potential threat to northern spotted owls that has not yet been shown is loss of genetic variation from population bottlenecks that can increase inbreeding depression and decrease adaptive potential. Here, we show recent genetic bottlenecks in northern spotted owls using a large genetic dataset (352 individuals from across the subspecies' range and 11 microsatellite loci). The signature of bottlenecks was strongest in Washington State, in agreement with field data. Interestingly, we also found a genetic signature of Pleistocene expansion in the same study areas where recent bottlenecks were shown. Our results provide independent evidence that northern spotted owls have recently declined, and suggest that loss of genetic variation is an emerging threat to the subspecies' persistence. Reduced effective population size (Ne), shown here in addition to field evidence for demographic decline, highlights the increasing vulnerability of this bird to extinction.
Publication type Report
Publication Subtype USGS Numbered Series
Title Genetics Show Current Decline and Pleistocene Expansion in Northern Spotted Owls
Series title Open-File Report
Series number 2008-1239
DOI 10.3133/ofr20081239
Edition -
Year Published 2008
Language ENGLISH
Publisher Geological Survey (U.S.)
Contributing office(s) Forest and Rangeland Ecosystem Science Center
Description iv, 13 p.
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