Abstract At the southern edge of their range, woodland jumping mice (Napaeozapus insignis) are associated with the high-elevation spruce-fir “sky islands” of the Southern Appalachians, one of the most fragmented and endangered ecosystems in North America. Consequently, gene flow is expected to be limited among sky island populations, which could result in strong geographic patterns of genetic structuring. Here, we present the first assessment of population genetic structure in woodland jumping mice of the Southern Appalachian Mountains of Eastern North America. We identified and sampled male and female woodland jumping mice from seven distinct mountains/mountain ranges in the Southern Appalachians of North Carolina, the Allegheny Mountains in the Central Appalachians of West Virginia, and the White Mountains in the Northern Appalachians of New Hampshire. Using a ∼350 base pair fragment of the mitochondrial DNA control region and 13 novel microsatellites, we estimated genetic diversity, relatedness among individuals, patterns of population genetic structure, and gene flow among populations. The geographic distribution of mtDNA haplotypes showed distinct haplogroups for the Northern Appalachian, Central Appalachian, and Southern Appalachian Woodland Jumping Mouse populations. Microsatellite analyses showed that within the Southern Appalachians, the northernmost and southernmost groups of spruce-fir sky island populations, separated geographically by the French Broad River, clustered separately. Surprisingly, however, there was minimal genetic differentiation among spruce-fir sky island populations on each side of the French Broad River; only the southernmost population was significantly differentiated from all others. Overall, females displayed greater genetic differentiation than males, suggesting differences in philopatry and dispersal among the sexes. Our study suggests that although Southern Appalachian sky islands serve as an important habitat for woodland jumping mice, it would be overly simplistic to conclude that the fate of this small mammal in the southern portion of its range is tied solely to that of this endangered ecosystem.
Watersmith et al. (Sun,) studied this question.