Persistence of DNA in carcasses, slime and avian feces may affect interpretation of environmental DNA data.

Christopher M Merkes,Mark P Gaikowski,S Grace Mccalla,Nathan R Jensen,Jon J Amberg,Richard C Willson

doi:10.1371/journal.pone.0113346

Abstract

The prevention of non-indigenous aquatic invasive species spreading into new areas is a goal of many resource managers. New techniques have been developed to survey for species that are difficult to capture with conventional gears that involve the detection of their DNA in water samples (eDNA). This technique is currently used to track the invasion of bigheaded carps (silver carp and bighead carp; Hypophthalmichthys molitrix and H. nobilis) in the Chicago Area Waterway System and Upper Mississippi River. In both systems DNA has been detected from silver carp without the capture of a live fish, which has led to some uncertainty about the source of the DNA. The potential contribution to eDNA by vectors and fomites has not been explored. Because barges move from areas with a high abundance of bigheaded carps to areas monitored for the potential presence of silver carp, we used juvenile silver carp to simulate the barge transport of dead bigheaded carp carcasses, slime residue, and predator feces to determine the potential of these sources to supply DNA to uninhabited waters where it could be detected and misinterpreted as indicative of the presence of live bigheaded carp. Our results indicate that all three vectors are feasible sources of detectable eDNA for at least one month after their deposition. This suggests that current monitoring programs must consider alternative vectors of DNA in the environment and consider alternative strategies to minimize the detection of DNA not directly released from live bigheaded carps.

Highlights

Aquatic invasive species (AIS) can have severe ecological and economic effects, and much effort has been put into the control of such species
Persistence of DNA Silver carp DNA was consistently detected from swabs collected from carcasses, while slime was found to be a variable source of DNA
All samples of silver carp slime adhering to metal trays taken on Day 1 and Day 4 contained silver carp DNA

Summary

Introduction

Aquatic invasive species (AIS) can have severe ecological and economic effects, and much effort has been put into the control of such species (reviewed in [1]). Some AIS are difficult to capture using conventional methodologies [4,5] Molecular tools, such as the analysis of environmental DNA (eDNA), have been used to quantify populations of elusive animals, identify sex distribution of animals in an area, assess biodiversity, and identify predators of vulnerable species [6,7,8,9,10,11,12,13,14,15,16]. The detection of eDNA in aquatic systems has begun to be used to monitor rare fish species, including AIS [4,17,18,19,20], reviewed in [21] This approach can be a very effective and efficient monitoring tool for detecting species at very low population densities, which is imperative for management

Methods

Results

Conclusion