Urocitellus endemicus

Recently, Hoisington-Lopez et al. (2012) elevated subspecies within U. brunneus, thereby recognizing Urocitellus endemicus as a distinct species. McLean et al. note the following in their 2025 publication: "These sister taxa are minimally diverged genetically (Hoisington-Lopez et al. 2012; McLean et al. 2016, 2022) but exhibit other differences (Yensen 1991; Hoisington-Lopez et al. 2012)." However, the American Society of Mammalogists' Mammal Diversity Database (June 22, 2025) retains endemicus as a subspecies of the Idaho Ground Squirrel (Urocitellus brunneus), providing "occasionally considered a distinct species, although this has not been followed in most subsequent publications and the data presented in the publication splitting the two species does not appear to strongly support a two species model."

Go to Idaho Ground Squirrel (Urocitellus brunneus)

Subspecies and support for Urocitellus endemicus as a distinct species

From Hoisington-Lopez et al. (2012): "Examination of our data sets suggests that, under the cohesion species concept, U. b. brunneus and U. b. endemicus could be treated as separate species. They are on separate evolutionary trajectories, because there is little to no migration between populations of these taxa, and apparently has not been gene flow since their late-Pleistocene divergence. Furthermore, they occupy different, nonoverlapping niches. Therefore, the 2 taxa exhibit neither demographic nor genetic exchangeability and conform well to the cohesion species concept. In addition, the 2 taxa differ greatly in morphology and behavior (Yensen 1991; Yensen and Sherman 1997), which further supports their status as distinct species."

References

McLean BS, Bell KC, Cook JA. 2022. SNP-based phylogenomic inference in Holarctic ground squirrels (Urocitellus). Molecular Phylogenetics and Evolution 169:107396. https://doi.org/10.1016/j.ympev.2022.107396

McLean BS, Jackson DJ, Cook JA. 2016. Rapid divergence and gene flow at high latitudes shape the history of Holarctic ground squirrels (Urocitellus). Molecular Phylogenetics and Evolution 102:174–188. https://doi.org/10.1016/j.ympev.2016.05.040

McLean BS, Rickart EA, Cook JA, Guralnick RP, Burgin CJ, Lohr K. 2025. Integrative species delimitation reveals an Idaho-endemic ground squirrel, Urocitellus idahoensis (Merriam 1913). Journal of Mammalogy (106) 405–429. https://doi.org/10.1093/jmammal/gyae135

Hoisington-Lopez JL, Waits LP, Sullivan J. 2012. Species limits and integrated taxonomy of the Idaho ground squirrel (Urocitellus brunneus): genetic and ecological differentiation. Journal of Mammalogy 93(2): 589-604.

Urocitellus brunneus (ASM Mammal Diversity Database #1001788) fetched June 22, 2025. Mammal Diversity Database. 2025. https://www.mammaldiversity.org/taxon/1001788/

Yensen E, Luscher MP, Boyden S. 1991. Structure of burrows used by the Idaho ground squirrel, Spermophilus brunneus. Northwest Science 65:93-100.

Yensen E, Sherman PW. 1997. Spermophilus brunneus. Mammalian Species (560): 1-5.