A recent study conducted by the University of Wisconsin – Madison found that some species of copepods such as Eurytemora affinis – tiny crustaceans measuring around a millimeter in length and roaming the coastal waters of oceans and estuaries around the world in large numbers – can evolve fast enough to survive in the face of rapid climate change.
“This is a dominant coastal species, serving as a very abundant and very nutritious fish food,” said study lead author Carol Eunmi Lee, professor of integrative biology at UW Madison. “But they are vulnerable to climate change.”
Because the salinity of the oceans is rapidly decreasing as the ice melts and precipitation patterns change, this saltwater species that evolved over the ages in high salinity waters must now adapt to harsher water. much softer in its environment.
In order to study how copepods react to drops in salinity, the scientists kept a population of Eurytemora affinis of the Baltic Sea in their laboratory and observed them for a few generations. After dividing the copepods into 14 groups of a few thousand each, they placed four of those groups in Baltic-like environments, while exposing the other ten groups to falling salinity levels that simulated the kind of pressure caused by climate change. For a total of ten generations, these groups saw their water gradually reduced to lower salinity levels.
To track evolutionary changes in the genomes of the tiny crustaceans, the researchers sequenced the genome of each copepod lineage at the start of the experiment, as well as after six and ten generations.
The analysis revealed that the strongest signals of natural selection – where changes were greatest and most frequent in groups exposed to low levels of salinity – were in areas of the genome important for the regulation of ions, such as sodium carriers.
“In salt water, there are a lot of ions, like sodium, that are essential for survival. But when you get to fresh water, those ions are valuable,” Professor Lee explained. copepods have to suck them up from the environment and cling to them, and the ability to do that relies on these ion transporters that we’ve found through natural selection.”
At the end of the experiment, copepods with certain genetic combinations of the ion transporter were more likely to survive, even though the salinity of their water decreased. Genetic variants found in copepods that managed to survive lower salinity in the laboratory are also common in copepods living in cooler regions of the Baltic Sea, the researchers said.
“This copepod gives us an idea of what is needed, an idea of the necessary conditions, which allow a population to evolve rapidly in response to climate change. It also shows how important evolution is to understanding our changing planet and how – or even if – populations and ecosystems will survive,” Professor Lee concluded.
The study is published in the journal Nature Communication.
By Andrei Ionescu, Terre.com Personal editor