Biogeographic patterns in Franklin’s ground squirrel, Spermophilus franklinii: implications for conservation

Franklin’s ground squirrel, Spermophilus franklinii, is one of the least studied and most poorly known of the ground squirrel species. In recent years, conservation interest in FGS has grown as perceived declines of this species in parts of its range have prompted it to be proposed for, or actually listed as, a state-endangered species. In contrast, in other parts of its range FGS is trapped as a nest-predator on waterfowl production areas. These regionally disparate views are noteworthy since FGS is considered monotypic, and presumably continuously distributed throughout its range. Therefore, current management and conservation initiatives are based on geo-political boundaries, which may or may not be biologically relevant. An understanding of the biogeography of FGS can help inform both management and conservation decisions of this species by: 1) identifying regionally unique populations, 2) mapping geographic structuring of populations, and 3) revealing insight into the processes responsible for shaping the observed population patterns. The purpose of my research, which began in 1999, is to examine geographic variation, from both morphological and genetic perspectives, in FGS throughout its entire range and the underlying biogeographic processes shaping those patterns. To date, morphological findings indicate a subtle size-gradient. Individuals at northern latitudes are characterized by smaller skulls than those at southern latitudes; there is no significant difference in body size across the latitudinal range of the species. Genetic analyses of the mitochondrial DNA control region indicate distinct geographic structuring. In eastern Nebraska, five populations are represented by six haplotypes. In the most extreme case, two of these populations separated by 30 km are differentiated by 8 base-pair changes within a 550 base-pair region. In contrast, in an area spanning 1000 km from northwest North Dakota to Athabasca, Alberta, six populations share the same haplotype. Additional populations, sampled in 2001 from areas where FGS are of conservation concern, are currently being incorporated into my dataset.

Jeffrey J. Huebschman

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