Evaluation of sample collection and storage protocols for surface eDNA surveys of an invasive terrestrial insect

Abstract

Environmental DNA surveys have revolutionized monitoring of rare or cryptic species and species inhabiting areas where conventional sampling is difficult or dangerous.Recent advancements within terrestrial environments include the capture of eDNA deposited by animals on surfaces such as tree bark and foliage, hereafter "surface eDNA." Notably, a technique which uses commercial paint rollers to aggregate surface eDNA has been deployed with success to detect the presence of forest insect pests providing a potentially powerful new management tool. However, before widespread adoption is feasible, the efficiency and logistics of roller sample collection and study design, especially relative to realistic survey conditions, must be evaluated. We compared the performance of two DNA preservation treatments-cold and ethanol-on their ability to reduce the loss of captured eDNA on rollers over time. Additionally, we evaluated how the detection probability of our target species, the spotted lanternfly (Lycorma delicatula), varied with sampling effort (time spent rolling per sample) and the initial quantity of eDNA present. Finally, we evaluated how the number of trees sampled per roller influenced the final concentrations of lanternfly eDNA remaining on the roller. We found storing rollers with ethanol or cold temperatures resulted in 3-10-fold greater concentrations of experimentally controlled eDNA relative to no treatment after 24 h. Detection probability declined as the amount of lanternfly eDNA decreased, but did not change in response to sampling effort over sample time (10-80 s/tree). Finally, recovered lanternfly eDNA decreased as more trees were sampled by a single roller-a 91% reduction after 7 trees-potentially due to captured DNA being transferred back from the roller onto the bark. Our results provide improved guidance for deploying roller surface eDNA methods for spotted lanternfly surveys, and for invasive insect pest surveillance and monitoring programs generally.

Environmental DNA Metabarcoding: A Novel Contrivance for Documenting Terrestrial Biodiversity

“…Mammals and potentially endangered species can also be detected using samples from natural saltlicks utilizing eDNA metabarcoding [ 104 ]. Using eDNA from the soil to trace mammals [ 105 ] is not only environment dependent but also dependent on mammal abundance and size [ 106 ]. Hence, knowledge of the ecological behavior of the mammal is essential for the sampling design [ 99 ].…”

Using surface environmental DNA to assess arthropod biodiversity within a forested ecosystem

“…At the same time, the number of samples in eDNA-based studies could be reduced, at least in theory, by pooling samples. For example, Peterson et al (2022) demonstrated that multiple trees can be sampled using the same roller swab before detection probability of DNA is reduced. Thus, increasing the number of trees per sample, or even pooling bark and understory samples, at each site may have increased the efficiency and detection power of our survey.…”

“…We avoided field sample contamination by wearing clean gloves, bleach sterilizing rollers and frames prior to deployment, and transporting gear within sterile bags (see Appendix S1 for additional details). After sampling, we placed the roller into an 800 mL (304 × 114 mm) sterile bag, added deionized (DI) water until ~30–40% of the roller was submerged (~130 mL), and massaged the roller for 15 s within the bag to dislodge and suspend DNA into the water (Peterson et al., 2022). Finally, we removed the roller from the bag and filtered the remaining water through a 5 μm polycarbonate track‐etched (PCTE) membrane filter housed in a sterilized 47 mm plastic filter holder (Whatman Swin‐Lok, Cytiva, Marlborough, Massachusetts, USA) using a peristaltic field pump and silicone tubing.…”

Development of novel LAMP and qPCR assays for rapid and specific identification of Bronze birch borer (Agrilus anxius)

“…(Valentin et al., 2020, 2021 ) and Peterson et al. (2022) have explored the feasibility of collecting eDNA in agricultural and forestry systems with sap‐sucking, phloem‐feeding insects that produce higher quantities of frass (i.e., honeydew). The viability of detecting these taxa in environmental samples is higher because of the higher abundance of eDNA.…”

“…As opposed to sampling eDNA in aquatic systems, sampling taxa in terrestrial systems using eDNA methodology is a developing field. Recent studies by Valentin et al (Valentin et al, 2020 and Peterson et al (2022) have explored the feasibility of collecting eDNA in agricultural and forestry systems with sap-sucking, phloem-feeding insects that produce higher quantities of frass (i.e., honeydew). The viability of detecting these taxa in environmental samples is higher because of the higher abundance of eDNA.…”