Matching a snail's pace: Successful use of environmental DNA techniques to detect early stages of invasion by the destructive New Zealand mud snail

Abstract

Early detection of invasive species allows for a more rapid and effective response. Restoration of the native ecosystem after an invasive population has established is expensive and difficult but more likely to succeed when invasions are detected early in the invasion process. Containment efforts to prevent the spread of known invasions also benefit from earlier knowledge of invaded sites. Environmental DNA (eDNA) techniques have emerged as a tool that can identify invasive species at a distinctly earlier time point than traditional methods of detection. Due to expected range expansion in eastern North America, we focus on the destructive New Zealand Mud Snail Potamopyrgus antipodarum (NZMS) invasion. We collected water samples from eight sites that prior evidence indicated were not yet invaded by the NZMS. After filtering these samples to collect eDNA, we used a species-specific probe with qPCR to identify NZMS eDNA. We found evidence for NZMS invasion at five of the eight sites, with later physical confirmation of mud snails at one of these sites. This study is the first example of successful detection of a previously unidentified invasive population of NZMS, setting the stage for further monitoring of at-risk sites to detect and control new invasions of this destructive snail. This study also shows potential opportunities for invasion monitoring offered by using low-cost efforts and methods that are adaptable for citizen science.