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Evolved beyond climate change, Tiny Marine Animals Provide New Evidence of Long Theorized Genetic Mechanism – Do You Stand Out?


A peer-reviewed publication

UNIVERSITY OF WISCONSIN-MADISON

MADISON – Some arthropods, tiny crustaceans with too big a place in aquatic food webs, may have evolved fast enough to survive rapidly changing climates, according to a study. just solved a longstanding question in the field of genetics.

Just over a millimeter long, the rat Eurytemora affinis sailing through the coastal waters of oceans and estuaries around the world in great numbers – mainly eaten by juvenile fish such as salmon, herring and anchovies.

Carol Eunmi Lee, professor in the Department of Integrative Biology at the University of Wisconsin-Madison and senior author of a new study on flippers published in the journal Nature Communications. “But they are vulnerable to climate change.”

The ocean’s salinity is changing rapidly as ice melts and rainfall changes, Lee explained.

Many flippers (and countless other animals) evolved in salt water. As their environment changes, they will have to adjust to maintain their body’s chemistry… or die.

“Salinity is a very strong environmental stress in aquatic habitats,” said David Stern, lead author of the study and a former postdoctoral researcher in Lee’s lab.

Lee, Stern, and the rest of the research team studied how some arthropods respond to that pressure. They keep a certain amount Eurytemora affinis from the Baltic Sea in their lab – small crustaceans that swim in saltwater like their home range and reproduce for generations.

The researchers then divided the flippers into 14 groups of several thousand each. Four control groups lived the experiment in environments such as the Baltic. The remaining 10 groups were exposed to declining salt levels, mimicking the kind of pressures caused by climate change. Each individual was reduced to a lower salinity with each new generation (about three weeks for this flipper) for a total of ten generations.

The researchers next sequenced the genomes of each arthropod lineage at the start of the experiment and repeated it after 6 and 10 generations, tracking evolutionary changes in their genomes. The strongest signals of natural selection – where changes are greatest and most common in groups stressed by reduced salinity – are in parts of the genome thought to be important in regulating ions , such as the sodium transporter.

“In salt water, there are a lot of ions, like sodium, that are essential for survival. But when you get to fresh water, these ions are precious,” says Lee. “So the flippers need to suck them out of the environment and stick to them, and the ability to do that depends on these ion carriers that we have found through natural selection. “

At the end of the experiment, the researchers found that footed crustaceans with certain genetic combinations of ion transporters were repeatedly able to survive successive generations, even when the salinity of the water decreases. In fact, the same gene variants, or alleles, found in flippers that have survived a decline in laboratory salinity are also common in the fresher parts of the Baltic Sea.

“Given the number of genes that we have that encode traits in flippers, there’s no way we can see the amount of parallelism we’ve done unless there’s something driving it,” Stern said. it”.

The evolutionary experiment is new evidence of a genetic mechanism known as parasitic aggressiveness, in which the positive effects of a gene variant are amplified when acting in combination with other important genes. It’s a theory that legendary UW genetics professor Madison and others championed nearly a century ago in opposition to additive evolution, the idea that the effects of a single gene Odds carry the same weight and the effects of multiple genes add up in a linear fashion.

Stern adds: “Computer simulations of evolution under our experimental conditions predict that additive evolution will give us much greater variation out of 10 lines. ours. “We don’t see that kind of variation.”

Epistasis has been largely untested because of the lack of experimental tools, but a large amount of genomic data from modern computer and sequencing simulations has made it possible to show active effusion during the process. parallel evolution and to describe the power of genetics in the study of climate change. In the new study, Stern, Lee and colleagues have shown that active hemostasis can promote parallel evolution of groups of animals by favoring repetitive allele groups through selection. nature.

“This arthropod gives us an idea of ​​what it needs, an idea of ​​what conditions are needed, to allow a population to grow rapidly in response to climate change,” Lee said. “It also shows how important evolution is to understanding our changing planet and how – or even whether – populations and ecosystems will survive.”

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JOURNEYS

Nature Communications

RESEARCH METHODS

Experimental study

From EurekAlert!



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