Researchers at the University of Trier (Trier) in Germany have developed a method for extracting and analyzing traces of insect DNA from dried plants.

“We have examined commercially available teas and herbs and have found DNA from up to 400 different insect species in a single tea bag,” explains junior professor Henrik Krehenwinkel.

When a bee flies to a flower to pollinate it, it leaves behind some saliva. An insect bites a leaf, a spider leaves threads of silk. All this is already enough to detect the DNA of insects, says Krehenwinkel.

Eggs or droppings are also suitable traces for the biogeographer. Whether there is a limit to what can be detected remains to be investigated. “In principle, however, single cells, for example from a beetle, will probably suffice,” Krehenwinkel explained.

According to the University of Trier, the innovation of the method developed by Henrik Krehenwinkel, Sven Weber, and Susan Kennedy is that environmental DNA (eDNA) is not extracted from the surface of plants, as usual, but from the ground and dried plant material. “Drying seems to preserve DNA especially well,” Krehenwinkel explained.

In plant cover, eDNA is not available for a long time because it is degraded by ultraviolet light or washed away by rain. Another limitation, he said, is that mainly plant surface insects are taken into account. “Now we can also detect which insects live inside the plant,” explained Krehenwinkel.

According to the researcher, the method presented in the scientific journal Biological Letters opens the possibility of analyzing ancient plant populations, for example, from museums, and comparing their colonization with the current one.

“In this way, it would be possible to find out what the insect community was like years ago when the plant was collected and what it is like today in that place.” This is especially important considering the mortality of insects.