Even the supposedly well-researched world of insects in Germany still has a lot of new things to offer. This is suggested by a study in which biologists used insect traps and DNA analyzes to search for clues to so-called “dark taxa” – as yet undiscovered species. The result: gene traces from thousands of previously unrecognized species were found in four families of flies and mosquitoes that were considered as examples.
So far we only know a fraction of the animal and plant species living on our planet – that much is clear. Especially in remote areas and in hard-to-reach habitats, there are countless species that no human has ever seen. In contrast, one could assume that there are hardly any hidden species left in the densely populated cultural landscape of Central Europe, which has been heavily influenced by human intervention.
Manhunt for the “dark taxa” of the insect world
But that is deceptive: Even with such a well-studied group of animals as insects, there are still large gaps in the taxonomy – even here in Germany. “Around 33,000 insect species are known in Germany, of which around two-thirds belong to the Diptera or Hymenoptera,” explain Caroline Chimeno from the Munich State Zoological Collection (SNSB-ZSM) and her colleagues. However, the Diptera in particular – flies and mosquitoes – include several families that are enormously species-rich, but whose full spectrum of species is not yet fully known. In addition, very small mosquito and fly species with a body length of less than two millimeters are difficult to identify based on their appearance.
For this reason, biologists are increasingly resorting to genetic methods of determination, including DNA barcoding in particular. Certain genetic identification sequences are determined from samples and compared with the entries in databases. Based on the matches, it can then be seen whether you are looking at a known species or one that has not been documented before. Animals that provide new, still unknown DNA sequences in such DNA barcoding studies are also referred to as “dark taxa” – dark species.
Thousands of unrecognized species
As part of the “German Barcode of Life – GBOL III: Dark Taxa” project, German scientists have set themselves the goal of tracking down and mapping such unrecognized species in Germany. The aim is to create a database with which every unknown animal found in Germany can be identified based on its DNA. As part of this project, Chimeno and her colleagues performed DNA barcoding of flies and mosquitoes in Bavaria. To do this, they caught insects over a period of six years at various locations in the Bavarian Forest, the Allgäu Alps and in Munich using flight traps and then analyzed the approximately 48,000 caught specimens for their DNA.
The analyzes revealed that around half of the DNA sequences identified had to belong to previously unknown Diptera species. Four families in particular, which had previously been classified as potentially under-researched, turned out to be particularly rich in dark taxa: midges (Chironomids), gall midges (Cecidomyiidae), humpback flies (Phoridae) and fungus gnats (Sciaridae). A good half of all unknown DNA barcodes came from these four families alone. “The gall midges were a particularly dramatic case: we discovered 1163 new barcode index numbers (BINs) from them alone, which corresponds to a quarter of all Diptera BINs,” report the scientists.
“We were surprised by the high proportion of undiscovered biodiversity in a supposedly well-studied country. Our investigations indicate that we have many more species of insects than we know,” says co-author Stefan Schmidt from the Munich State Zoological Collection. It is all the more important to research this undiscovered diversity more closely – especially in view of the alarming decline in insects in Germany and worldwide. “With “GBOL III: Dark Taxa” we are creating an important scientific basis for better understanding the overall decline in insects in Germany.”
Source: State Natural Science Collections of Bavaria; Specialist article: Insects, doi: 10.3390/insects13010082