The sooner that you know an invasive species is present in your local environment, the better the chances that you can control it before it becomes unmanageable. It was with this in mind that researchers from the University of Illinois recently detected the presence of a species of invasive freshwater clam, by looking for its cast-off DNA in lake water.

Working in collaboration with colleagues from Rice University, the University of Notre Dame and the University of Nevada at Reno, the scientists performed an eDNA assay – eDNA stands for "environmental DNA," and refers to DNA that is passed into the environment in the form of excretions and other biomaterials.

"It's an emerging tool that has the potential to be better at detecting rare species in some cases, relative to some of our more traditional survey methods," says U of I aquatic ecologist Eric Larson. "There's a lot of DNA floating around in a lake or a stream, and if we can capture and identify it, it can tell us what organisms are present, including invasive species."

To that end, the team used the technology to search for the DNA of a type of small clam known as Corbicula. Native to East Asia, it has spread throughout Europe and the US, sometimes becoming so plentiful that it clogs pipes and otherwise damages infrastructure.

Out of 11 California and Nevada lakes tested, the clam's DNA was detected in four where the animal was already known to exist, and it wasn't found in the other seven lakes, in which the clam hasn't been reported.

"Because we now know that the eDNA assay works well, we want to apply it to some other questions," says Larson. "Is there a best time of the year to use eDNA to detect this invader? If we can't find their DNA in the winter, does it spike in the summer? Do floods mobilize a lot of DNA, making it easy to detect or does flooding dilute the DNA that's there?".

A paper on the research was recently published in the journal Management of Biological Invasions.

Source: University of Illinois