Abstract
The Idaho ground squirrel, which consists of a northern (Spermophilus brunneus brunneus) and a southern subspecies (S. b. endemicus), has suffered from habitat loss and fragmentation, resulting in a reduction in both numbers and geographic range of the species. The northern Idaho ground squirrel (NIDGS) is listed as a threatened subspecies under the Endangered Species Act, and the southern Idaho ground squirrel (SIDGS) is a candidate. Because Idaho ground squirrel populations are small and often isolated, they are susceptible to inbreeding and loss of genetic diversity through drift. This research evaluates levels of genetic diversity and patterns of population divergence in both subspecies of Idaho ground squirrels. We hypothesized that NIDGS would exhibit lower genetic diversity and greater population divergence due to a longer period of population isolation relative to most SIDGS populations. Genetic diversity and divergence were quantified using 8 microsatellite loci. Contrary to expectations, SIDGS populations exhibited consistently lower levels of microsatellite diversity. Additionally, NIDGS exhibited only modest divergence among populations, while divergence levels among SIDGS populations were highly varied. Preliminary evaluations of mitochondrial DNA diversity and structure revealed lower diversity in NIDGS and some differences in gene flow that warrant further study. Based on our results, we suggest different management strategies for the two subspecies. Habitat restoration appears to be the most desirable conservation strategy for NIDGS populations. In contrast, low genetic diversity observed in SIDGS may warrant supplementation of isolated populations through translocations or captive breeding to mitigate further loss of genetic variability.
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Acknowledgments
This research was funded by the Idaho Department of Fish and Game through the Wildlife Conservation and Restoration Program, the Bureau of Land Management through the Challenge Cost Share Program, Idaho Power Company, and American Society of Mammalogists Grants-in-Aid of Research. Funding for A. Garner was provided by the Berklund Foundation, University of Idaho, and the Idaho Department of Fish and Game. We also thank the U.S. Fish and Wildlife Service, the U.S. Forest Service, R. Howard, B. Haak, J. Rohlman, L. Schultz, and B. Gould for logistical support in the field. Thanks also to E. Yensen, S. Brunsfeld, and two anonymous reviewers for comments on the manuscript, and to J. Clark, K. Russell, C. Harris, T. Holthuijzen, and D. Evans-Mack. Assistance with sample collection was provided by J. Munger, J. Barrett, D. Collins, D. Sparber, J. Kissler, J. Lee, K. Mallea, R. Collier, M. Collie, K. Lauden, and J. Beals. We appreciate the cooperation of landowners M. Soulen and J. Hinson, J. Dyer and F. Anderson, J. Little, A. Brailsford, P. Skow, and B. Mack, as well as the Rolling Hills Golf Course and Hillcrest Cemetery management. Assistance with DNA extraction was provided by S. Bajimaya, B. Nichols, and C. Holmberg, and mitochondrial sequencing was completed by C. Anderson. We also thank E. Strand for assistance with Arcview and D. Onorato for assistance with Arlequin. Novel microsatellite loci for the southern Idaho ground squirrel were isolated by Genetic Identification Services, Chatsworth, CA.
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Garner, A., Rachlow, J. & Waits, L. Genetic diversity and population divergence in fragmented habitats: Conservation of Idaho ground squirrels. Conserv Genet 6, 759–774 (2005). https://doi.org/10.1007/s10592-005-9035-3
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DOI: https://doi.org/10.1007/s10592-005-9035-3