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 output: Contribution to journalArticlepeer-review

16 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)1233-1241
Number of pages9
JournalConservation Genetics
Issue number6
StatePublished - Dec 2013


  • Arizona
  • Conservation
  • Effective population size
  • Endangered species
  • Inbreeding

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics


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