Researchers from the University of Gothenburg assisted the Swedish Environmental Protection Agency in their investment in new DNA methods for environmental monitoring and research – the study led to the discovery of up to 200 new generations of worm species, among other things.
Life on our planet consists of countless species of organisms, including bacteria, fungi, algae, plants, and animals. One political goal is to preserve as much of this diversity as possible. Therefore, the Swedish Environmental Protection Agency has funded eight research projects that focus on the development and implementation of new DNA methods to find more modern ways of monitoring the environment.
One way to assess the health of a deciduous forest is to estimate the amount of worms in the soil fauna. However, simply counting visible worms as individuals is a blind tool for understanding the situation from a diversity perspective. Additionally, it is crucial to have a precise understanding of how many and which worm species are present in the environment. The application of molecular, DNA-based methods for species identification is increasingly becoming common in environmental research and monitoring.
Christer Erséus, a retired professor from the University of Gothenburg, dedicated a significant portion of his research career to this very topic. He led one of the research projects focusing on a group of common small animals, the clitellate worms (Clitellata), both in water and on land.
“We have identified specific DNA markers that can serve as a kind of barcode for easily determining different species of clitellate worms. With the help of these markers, it is now possible to identify the DNA traces of various species in nature (known as environmental DNA or eDNA), which, if expanded to other organisms, could theoretically uncover all species coexisting in a particular environment,” says Christer Erséus.
However, for this approach to work, one would need to have previously analyzed the DNA profile specifically for each species, and mapping all Swedish organisms in this way would take a long time. In the project, researchers only examined the DNA of the focal groups. Using DNA samples obtained from 21,000 worm individuals mostly from northwest Europe, 602 species of clitellate worms could be identified, but not all of them can be associated with known species.
“For many species that we currently characterize molecularly with DNA, we estimate that between 150 and 210 remain undescribed under suitable scientific names. They are simply new to science, and the uncertainty in the numbers stems from our DNA data also distinguishing species not represented by adult individuals in our material,” says Christer Erséus. He further explains that without access to adult animals, these types of worms cannot be confidently assigned to a specific known species.
Earthworms and leeches are the more conspicuous clitellate worms, but hundreds of small species, only a few millimeters in size, are also included in the group. Clitellate worms play important roles in the decomposition of organic matter in nature. However, leeches are predators or parasites. The goal of the project is to compile virtual reference libraries of DNA barcodes for all species.
“The project has taught us a lot about the taxonomic and genetic complexity of our animal group. The conclusion we have reached is that this reference database and similar studies for other organism groups should continue. In the long run, it can mean a lot to monitor species diversity in an apparently changing world,” concludes Christer Erséus.