We biological beings are messy things, leaving bits of our former selves behind everywhere we go – even in the air. This trail of self includes various secretions like saliva, discarded waste. and our constantly shedding outer layers like dead skin cells – many of which contain our unique DNA signatures.
Bugs are no exception. From spiders to beetles, invertebrates also leave a snail trail of evidence in their wake – including over any growing tea leaves they may have munched on or even just brushed by.
Scientists have just detected evidence of a staggering 1,200 different species of invertebrates in only 40 samples of dried teas and herbs.
"What really surprised me was the high diversity we detected," Trier University ecological geneticist Henrik Krehenwinkel told Shawna Williams at The Scientist. "We found in green tea up to 400 species of insects in a single tea bag."
In total, researchers found the trails of 3,264 invertebrates including predators, herbivores, detritivores, and parasites from around the world, in the samples of commercially produced teas and herbs bought in German grocery stores. There were DNA traces of spiders, cockroaches, mites, flies, butterflies, mantids, and lots more.
Krehenwinkel and colleagues suspect the stunning diversity is due to how the dried herbs (tea leaves, mint, and parsley) are processed – as they are ground up, the DNA from all parts of the field where the crops are grown (likely including some stray whole bugs and their eggs) gets preserved, mixed, and spread through the entire batch.
The resulting environmental DNA (eDNA) provides the researchers with enough information to pinpoint where the plants were grown, as well as a snapshot of the invertebrate biodiversity present in the area.
"Dried plant material appears excellently suited as a novel tool to monitor arthropods and arthropod–plant interactions, detect agricultural pests, and identify the geographical origin of imported plant material," the team wrote in their paper.
However, they caution, "[w]hile our eDNA approach represents an important development for arthropod monitoring, it should be noted that it is not free of biases and will require further standardization in the future."
For example, scientists don't yet know if certain species would go undetected because they leave less of a genetic trail behind on these plants, despite being prevalent in the surrounding environment.
Regardless, this method clearly provides a lot of information that we couldn't easily access before. So it could be used to simplify environmental monitoring, and possibly even help expand species records back through time, using museum herbarium specimens.
"Plant collections in museums, could they actually be useful to understand how insect communities have changed?" asks Krehenwinkel in The Scientist. "When insect decline studies were first published, a lot of people complained [that] there is no real long-term data."
Krehenwinkel and the team are now working on this to try and to find out.
Hopefully, these records are obtainable as we all rely on insects and other invertebrates to help run our life support system – our natural environment. With massive environmental upheaval already underway, reading tea leaves really could provide us with some vital information.
This research was published in Biology Letters.