Conservation Genetics

, Volume 14, Issue 6, pp 1233–1241 | Cite as

Severe reduction in genetic variation in a montane isolate: the endangered Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis)

  • Robert R. Fitak
  • John L. Koprowski
  • Melanie Culver
Research Article


The Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis; MGRS) is endemic to the Pinaleño Mountains of Arizona at the southernmost extent of the species’ range. The MGRS was listed as federally endangered in 1987, and is currently at high risk of extinction due to declining population size and increasing threats. Here we present a genetic assessment of the MGRS using eight nuclear DNA microsatellite markers and a 472 bp fragment of the mitochondrial cytochrome b gene. We analyzed 34 MGRS individuals and an additional 66 red squirrels from the nearby White Mountains, Arizona (T. h. mogollonensis). Both nuclear and mitochondrial DNA analyses revealed an extreme reduction in measures of genetic diversity relative to conspecifics from the White Mountains, suggesting that the MGRS has either experienced multiple bottlenecks, or a single long-term bottleneck. Additionally, we found a high degree of relatedness (mean = 0.75 ± 0.18) between individual MGRS. Our study implies that the MGRS may lack the genetic variation required to respond to a changing environment. This is especially important considering this region of the southwest United States is expected to experience profound effects from global climate change. The reduced genetic variability together with the high relatedness coefficients should be taken into account when constructing a captive population to minimize loss of the remaining genetic variation.


Endangered species Conservation Effective population size Inbreeding Arizona 



We thank A.Naidu, A. Ochoa, J. Leonard, and two anonymous reviewers for their helpful comments on this manuscript. We would also like to thank the individuals who contributed to collecting tissue samples, especially K. Munroe and V. Greer, and T. Dee, D. Sotelo and G. Reida for help with DNA extractions. This research was supported through an Arizona Game and Fish Heritage Program grant to MC and JLK and funds from the USDA Forest Service and the University of Arizona to JLK. RRF was supported by a Science Foundation Arizona fellowship and an NSF-IGERT fellowship in comparative genomics. Mention of specific products does not constitute endorsement by the U.S. Geological Survey.


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Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  • Robert R. Fitak
    • 1
  • John L. Koprowski
    • 1
    • 2
  • Melanie Culver
    • 1
    • 2
    • 3
  1. 1.Graduate Interdisciplinary Program in GeneticsUniversity of ArizonaTucsonUSA
  2. 2.School of Natural Resources and the EnvironmentUniversity of ArizonaTucsonUSA
  3. 3.U. S. Geological Survey Arizona Cooperative Fish and Wildlife Research Unit, School of Natural Resources and the EnvironmentUniversity of ArizonaTucsonUSA

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