Biology: Traces of 400 species of insects found in tea

Researchers at the University of Trier have developed a method for extracting and evaluating insect genetic material from dried plants. “We tested commercially available teas and herbs and found DNA from up to 400 different insect species in a single tea bag,” said Junior Professor Henrik Krehenwinkel.

When a bee flies to a flower to pollinate, it leaves a little saliva behind. A beetle stings a leaf, a spider leaves silk threads. According to Krehenwinkel, all this is already enough to detect the DNA of insects. Eggs or droppings are also convenient clues for the biogeographer. Should we further investigate whether there is a limit to what can be detected? “In principle, however, single cells, like those of a beetle, are probably sufficient,” Krehenwinkel explained.

Innovative method better detects environmental DNA

According to the University of Trier, the innovation of the biomonitoring method is that environmental DNA (environmentalDNA, abbreviated eDNA) is not taken from plant surfaces as usual, but from crushed, dried plant material. “Drying seems to preserve DNA particularly well,” Krehenwinkel explained.

eDNA is not available for long on the plant shell because it is degraded under UV light or washed away by rain. Another limitation is that insects on the plant surface are mainly considered. “Now we can also prove which insects live in the plant,” explained Krehenwinkel.

According to the researcher, the method presented in the professional journal “Biological Letters” opens up the possibility of analyzing old plant populations, for example from museums, and comparing their colonization with today’s. ‘This would allow us to find out what the insect community looked like many years ago when the plant was collected and what it looks like at the site today.’ This is especially important in view of insect mortality.

In addition, the method could also be used in criminology. As stated in the announcement, the actual geographical origin of plants can be reliably determined using eDNA. In this way, customs could determine whether the imported types of tea really come from the specified countries, or where other plants, such as drugs, come from.

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