A conservation assessment of Franklin's ground squirrel (Spermophilus franklinii Sabine 1822): Input from natural history, morphology and genetics.

摘要

My dissertation research represents an important contribution to the literature on Franklin's ground squirrel, Spermophilus franklinii , and is the first systematic attempt to inform its conservation and management. In the southeastern portion of its geographic range, S. franklinii has been listed or proposed for listing as a state-endangered species, in contrast to central and northern portions where it is trapped as a nest-predator on wildlife refuges. Because knowledge of the extent and type of geographic variation found within a species is critical to its conservation and management, the regional disparity in views concerning S. franklinii served as the impetus for my study of its patterns of geographic variation. Morphometric analyses of 11 skull measurements indicated little morphological variation in S. franklinii, with the exception of a significant latitudinal cline in size displayed by both sexes: individuals from southern latitudes were generally larger than individuals from northern latitudes. Genetic analyses, based on the mitochondrial DNA control region, also indicated little geographic variation. These findings support the monotypic status of the species. The distribution of genetic variation in S. franklinii was not evenly distributed throughout its geographic range. Low genetic variation was found in northern and southeastern regions—reflective of range expansion events—in contrast to the southwestern region, which exhibited the greatest genetic variability and coincides with the region that has been occupied by S. franklinii since the Pleistocene. These patterns conform remarkably to expectations for a species that occupies post-glacially colonized regions, which include the northern portions of S. franklinii's range. Although S. franklinii, which prefers savanna-like habitat, may have an affinity for northern regions, the current concern for declining southern populations is warranted, particularly because these populations contain the greatest portion of the species' genetic variability. The past response of S. franklinii to warming periods, range shifts north, may signal a cause for additional concern for the loss of southern populations in the face of current global warming trends.