Validation of a nutria (Myocastor coypus) environmental DNA assay highlights considerations for sampling methodology

Abstract

Nutria (Myocastor coypus) is a semiaquatic rodent species that is invasive across multiple regions within the United States. Here, we evaluated a qPCR assay previously described for use in Japan for application across invasive populations in the United States. We also compared two environmental DNA sampling methodologies for this assay: field filtration of large volumes of water passed through filters versus direct sampling of small volumes of water. We validated assay specificity, generality, and sensitivity, compared assay performance between two independent laboratories, and successfully tested the assay in situ on a known wild population. The filtration method required fewer samples for environmental DNA detection than direct sampling, but the choice of methods should be assessed based on specific field conditions and time and budget considerations. Our extensive assay validation and comparison across laboratories suggest that the assay is ready to be applied in environmental DNA monitoring of nutria throughout the United States.

Field validation of an eDNA assay for nutria illuminates a role in invasive species management

“…Similar to Mangan et al. (2023), this study confirmed that the assay was able to detect nutria in the field, and that filtering water in the manner practiced was effective for DNA capture. The findings revealed a link between water levels and nutria detection, with higher water levels generally associated with higher concentrations of eDNA.…”

“…Initially introduced from South America to the United States for fur farming during the late 1800s, nutria established wild populations throughout the country (Carter & Leonard, 2002). Notable hotspots of nutria invasion include areas near the Gulf of Mexico, the Pacific Northwest, and the mid‐Atlantic region of the USA (Mangan et al., 2023). Their foraging habits involve digging through soil in search of roots and rhizomes and result in the destruction of wetland vegetation (Jojola et al., 2005; LeBlanc, 1994).…”

“…An eDNA qPCR assay for detecting nutria was initially developed in Japan (Akamatsu et al., 2018) and recently lab‐validated using nutria tissue samples from various states in the United States, including California, Louisiana, Oregon, Maryland, and Virginia (Mangan et al., 2023). The assay was tested against co‐occurring species to confirm specificity, and subsequent field validation took place in Oregon (Mangan et al., 2023). Current recommendations emphasize re‐validating eDNA assays in new geographic areas that might encompass genetic variation for quality control (Langlois et al., 2021; Thalinger et al., 2021).…”