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Data and code from: Drivers behind spatiotemporal variation in environmental DNA: An assessment using a rare aquatic salamander, the Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis)

Tomke, Sarah1; Price, Steve2

Published Mar 03, 2026 on Dryad. https://doi.org/10.5061/dryad.tx95x6b7m

Data files

Abstract

Environmental DNA (eDNA) sampling has become a common tool for monitoring rare and declining aquatic species. However, results can be biased by the spatiotemporal variation in eDNA signals, yet the biological and environmental factors that cause this variation are not well understood. Here, we examined the seasonal and fine-scale (< 100 m) longitudinal variation in eDNA concentration and detection in situ for a rare aquatic salamander, the Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis). We also applied multivariate generalized linear mixed-effects models to investigate how physical and hydrological stream characteristics influence eDNA concentration estimates and detection rates. Both metrics spiked during the hellbender breeding season, but remained low at other times of the year. This was primarily driven by one site in which hellbenders are dense and actively reproducing; once this site was removed from analyses, temporal variation in eDNA signals was no longer observed. No fine-scale spatial eDNA pattern emerged, but concentrations and detections were highly variable across temporal and spatial replicates within sites, emphasizing the importance of collecting replicate eDNA samples at multiple scales. Only PCR inhibitors present in our samples significantly reduced concentrations and detections; however, general negative relationships were still apparent with flow velocity. Increased surface water temperature and pH were also tenuously associated with eDNA concentrations but did not influence detections. Our study contributes important knowledge regarding biological and environmental factors driving eDNA spatiotemporal variability, facilitating a refinement in eDNA sampling strategies for hellbenders and other rare aquatic organisms so that accurate scientific inferences about their populations can be made.