Legacy of historical disturbance shapes modern genetic diversity in a high-elevation salamander

Maintaining the genetic diversity of wildlife populations is important as reductions in genetic diversity can have negative consequences like reduced fitness caused by inbreeding depression or increased risk of extirpation. Anthropogenic disturbance can have long-lasting impacts on the genetic diversity of wildlife populations. Here, we evaluated how historic timber harvesting and settlement shape modern spatial patterns of genetic diversity in the narrow-range endemic red-cheeked salamander ( Plethodon jordani ) in the Great Smoky Mountains National Park (GSMNP). Using microsatellite genotypes from 549 individuals across 23 sites, we quantified genetic diversity, tested for isolation by distance, and assessed the relationship between genetic diversity and historic disturbance and elevation. We found spatial variation in genetic diversity and statistically significant isolation by distance. Sampling sites located near historically harvested or settled areas exhibited reduced genetic diversity, but this negative effect was moderated at high elevations where salamander densities are higher and microhabitats are more favorable. Additionally, historic disturbance was associated with reduced modern understory density, a habitat feature that positively influences salamander abundance. Our findings demonstrate that land-use legacies continue to shape both forest structure and the genetic diversity of a narrowly distributed amphibian nearly a century after large-scale timber harvest ceased. These results highlight the importance of incorporating historic landscape change into conservation planning, especially for high-elevation endemics whose long-term persistence may depend on maintaining genetic diversity and adaptive capacity.