Detection of plethodontid salamanders using traditional and environmental DNA surveys in an urban setting
Urbanization threatens to alter many watersheds in the eastern United States, often resulting in the degradation of smaller streams. These highly disturbed systems may result in many local extirpations of sensitive species, especially those that utilize both terrestrial and aquatic habitats, such as the lungless salamanders (family Plethodontidae). We compare two methods of detecting plethodontid species presence in urban streams: traditional manual search methods and collection of environmental DNA samples (eDNA). Across 19 sites in urban Atlanta, Georgia, USA, we found that traditional manual surveys and eDNA sampling did not significantly differ in mean number of plethodontid species detected. Traditional surveys resulted in more species-level false negatives, likely due to low density or secretive nature of some species, while eDNA sampling resulted in missing data for entire sites, likely due to PCR inhibition. We uncovered a significant, negative relationship between plethodontid species richness and percent impervious surface cover of the watershed, highlighting the negative effects of urbanization on biotic community health. With more streams impacted by urbanization, it is important to develop sound methods for inventory and monitoring efforts. We recommend a combination of both traditional and eDNA methods.