WSL monitors Switzerland nationwide for priority quarantine organisms – i.e., particularly harmful pests that are not widespread in our country and could cause considerable economic, ecological, or social damage if introduced.

For this, we use insect traps and analyse the catches morphologically, i.e., based on their visible characteristics.

However, this classical identification of insects and arachnids under the microscope is labor-intensive and requires a great deal of expertise – which is dwindling for some taxonomic groups.

That is why we are also exploring the possibilities of DNA metabarcoding: we gently extract DNA from the bodies of captured animals using a buffer solution and use it for species identification. We have also tested whether we can use the trapping fluid directly for species identification, as it contains the DNA of the captured animals (eDNA).
 

The two DNA methods yield different species compositions. One possible reason for this is that DNA from species with hard exoskeletons – such as many beetles – is clearly in trapping fluids.

Significantly fewer beetle species are detected in the trap fluid than with the other two methods. In return, additional species sometimes appear there whose DNA has been introduced into the trap as tiny fragments, for example by the wind.

The choice of method therefore influences the range of species detected. We are currently investigating other possible causes in order to be able to select the appropriate method depending on the research question at hand.

DNA metabarcoding offers a valuable addition here: it opens up new insights and expands the possibilities in modern species monitoring.

Classical morphological identification remains indispensable. It is not only the basis of taxonomic expertise, but also important for environmental education – because we can only protect what we recognize.