Evolving To Outpace Climate Change, Tiny Marine Animal Provides New Evidence of Long-Theorized Genetic Mechanism

Peer-Reviewed Publication


MADISON — Some copepods, diminutive crustaceans with an outsized place in the aquatic food web, can evolve fast enough to survive in the face of rapid climate change, according to new research that addresses a longstanding question in the field of genetics.

Barely more than a millimeter long, the copepod Eurytemora affinis paddles its way through the coastal waters of oceans and estuaries around the world in large numbers — mostly getting eaten by juvenile fish, like salmon, herring and anchovy.

“This is a dominant coastal species, serving as very abundant and highly nutritious fish food,” says Carol Eunmi Lee, professor in the University of Wisconsin–Madison’s Department of Integrative Biology and senior author of a new study on the copepods published in the journal Nature Communications. “But they’re vulnerable to climate change.”

Ocean salinity, Lee explains, is changing rapidly as ice melts and precipitation patterns change: “These copepods are a saltwater species that now needs to adapt to much fresher water in their environment.”

Many copepods (and innumerable other animals) evolved in salty water. As their environment changes, they will have to adjust to maintain their body chemistry … or die off.

“Salinity is a very strong environmental pressure in aquatic habitats,” says David Stern, lead author of the study and a former postdoctoral researcher in Lee’s lab, now working at the National Biodefense Analysis and Countermeasures Center.

Lee, Stern and the rest of the research team studied how some copepods responded to that pressure. They kept a population of Eurytemora affinis from the Baltic Sea in their lab — the small crustaceans swimming in water just as salty as their home range and reproducing through several generations.

The researchers then split the copepods into 14 groups of a few thousand each. Four control groups lived out the experiment in the environment like the Baltic. The other 10 groups were exposed to declining salt levels, mimicking the sort of pressure caused by climate change. Each had their water reduced to lower salinity at each new generation (about three weeks for this copepod) for a total of ten generations.

The researchers next sequenced the genomes of each line of copepods at the beginning of their experiment and again after six generations and 10 generations, tracking evolutionary changes across their genomes. The strongest signals of natural selection — where changes were largest and most common across the groups stressed by falling salinity — were at parts of the genome believed to be important in regulating ions, such as sodium transporters.

“In saltwater, there are a lot of ions, like sodium, that are essential for survival. But when you get to freshwater, these ions are precious,” says Lee. “So, the copepods need to suck them up from the environment and hang on to them, and the ability to do that relies on these ion transporters that we found undergoing natural selection.”

At the end of the experiment, the researchers found that copepods with certain genetic combinations of the ion transporter were, repeatedly, more likely to survive through successive generations, even as the salinity of their water decreased. In fact, the same gene variants, or alleles, found in the copepods that survived the salinity decline in the laboratory are also common in the fresher regions of the Baltic Sea.

“With the number of genes we have encoding the traits in our copepods, there’s no way we would see the amount of parallelism we did unless something was driving it,” says Stern.

The evolution experiment is new evidence of a genetic mechanism called positive epistasis, in which the positive effect of a variant of a gene is amplified when working in combination with other key genes. It’s a theory that legendary UW–Madison genetics professor Sewall Wright and others championed nearly a century ago in counterpoint to additive evolution, the idea that the effect of each single gene carries the same weight, and the effects of many genes add up in a linear fashion.

“Computer simulations of evolution in our experimental conditions predict that additive evolution would have given us much greater variation among our 10 lines,” adds Stern. “We didn’t see that kind of variation.”

Epistasis had gone largely untested for lack of experimental tools, but the large amounts of genomic data from modern sequencing and computing simulations made it possible to show positive epistasis at work in parallel evolution and to describe the power of genetics for studying climate change. Stern, Lee and colleagues show in the new study that positive epistasis can drive the parallel evolution of groups of animals by favoring sets of alleles repeatedly through natural selection.

“This copepod gives us an idea of what it takes, an idea of what the conditions are needed, that enable a population to evolve rapidly in response to climate change,” says Lee. “It also shows how important evolution is for understanding our changing planet and how — or even whether — populations and ecosystems will survive.”



Nature Communications


Experimental study

From EurekAlert!

2.7 9 votes
Article Rating
Newest Most Voted
Inline Feedbacks
View all comments
July 15, 2022 6:25 am

Copepods know how to cope….but I fear a study soon will reveal their struggle with increasing CO2….will they cope with CO2 increases?

Bryan A
Reply to  Anti-griff
July 15, 2022 7:02 am

Considering Copepods have been around for 289 million years, and exist in both Fresh and Salt Water environments, I would say that they are almost as resilient as Water Bears

July 15, 2022 6:34 am

So the model was wrong? Color me surprised.

July 15, 2022 6:42 am

And just when is the Great Melting to begin? It hasn’t started yet.

Bryan A
Reply to  DHR
July 15, 2022 8:09 am

The great melting started about 12,000 years ago, when the great Laurentide Ice Sheet began receding. It will end once we begin the next Big Freeze cycle

Thomas Bakewell
July 15, 2022 7:01 am

Weaponizing copepods?

Bryan A
Reply to  Thomas Bakewell
July 15, 2022 8:10 am

Attack of the CopePod People

Reply to  Bryan A
July 15, 2022 8:24 am

Attack of the Cope Pod People

john harmsworth
Reply to  Fraizer
July 15, 2022 1:57 pm

The Can’t Cope-apods. Non-existent brains don’t know they are in crisis. Giant brains imagine it’s there when it isn’t. Pretty funny, really.

Gordon A. Dressler
July 15, 2022 7:04 am

From the above article’s third-to-last paragraph:

“Computer simulations of evolution in our experimental conditions predict that additive evolution would have given us much greater variation among our 10 lines,” adds Stern. “We didn’t see that kind of variation.”

Gee . . . If this had been the very first paragraph, I could have saved the time of reading the 13 preceding paragraphs that it took to reach this key admission.

Furthermore, given that prior to the “Quarternary” Ice Age that we are currently in, Earth had four previous Ice Ages:
— the “Huronion” that lasted about 300 million years
— the “Cryogenian” that lasted about 90 million years
— the “Andean-Saharan” that lasted about 40 million years
— the “Karoo glaciation” that lasted about 100 million years.
All of these have had relatively quick entrances and exits. Why then is anyone surprised that life forms are able to adapt to, and survive, “rapid climate change” (a phrase that is conveniently left undefined in the above article, hah!).

The truth has been out there all along, for anyone willing to “learn the lessons of history”.

Frank from NoVA
July 15, 2022 7:33 am

Something is not making sense to me. First, they say that ‘positive epistasis’ has an amplifying effect on genetic variation compared to ‘additive evolution’, and then they say that their computer simulations predicted that ‘additive evolution would have given us much greater variation’.

Gordon A. Dressler
Reply to  Frank from NoVA
July 15, 2022 7:41 am

Of course it doesn’t make sense. Computer simulations are often misused, resulting in GIGO.

Reply to  Frank from NoVA
July 15, 2022 1:58 pm

some test plots getting better, some getting worse, in different ways — greater variation

john harmsworth
Reply to  Frank from NoVA
July 15, 2022 2:00 pm

Give ’em a break! They’re making it up as fast as they can.

Jane Michaels
Reply to  Frank from NoVA
July 16, 2022 5:01 am

It implies to me that the co-amplification when modeled caused wider prevalence of successful gene(s) across the population reducing diversity compared to additive evolution

Right-Handed Shark
July 15, 2022 7:44 am

This appears to be another start-with-a-conclusion-and-backfill study.

H. D. Hoese
July 15, 2022 7:51 am

Copepods have fascinating survival skills, some act like flying fish when chased (first paper), some are euryhaline and tolerate lots of salinity changes. Some (second paper) in water males have more speed, females longer duration. Real science with homework back to 1890 when jumping was known as a sign of fish showing up. Both open access.

Gemmell, B. J.,et al., 2012. Plankton reach new heights in effort to avoid predators. Proceedings Royal Society. B. doi:10.1098/rspb.2012.0163.
Buskey, E. J., et al., 2002. Escape behavior of planktonic copepods in response to hydrodynamic disturbances: High speed video analysis. Marine Ecology Progress Series. 235:135-146.   doi:10.3354/meps235135

May be a decent genetic study, lots of such such work going on today, but they don’t know much about the ocean, Wisconsin long way off. Haven’t checked these references, probably unread boilerplate, a now too common feature in papers. Both of these statement are dubious, and there are viable species more tolerant to replace them. 5psu (ppt) is of small consequence in estuaries and oceans except at extremes. Temperature and topography more important in most places and we certainly don’t know enough about historical salinities.

“Among the most ecologically and economically impactful consequences of global climate change is the rapid change in ocean salinity throughout the globe80. Due to massive increases in ice melt and precipitation, salinity is predicted to decline at unprecedented rates in higher latitude coastal waters, by up to 5 PSU in the coming decades42,43,44. Salinity is arguably the strongest driver of aquatic biogeographic distributions81,82,83”

Reply to  H. D. Hoese
July 15, 2022 2:02 pm

On the one side: the oceans
On the other side: melting glaciers
what is the ratio on their relative volumes?
Might this be relevant to :rapid change in ocean salinity throughout the globe”?

Josh Scandlen
July 15, 2022 7:53 am

Wake me when they change species

Gordon A. Dressler
Reply to  Josh Scandlen
July 15, 2022 8:09 am


Bryan A
Reply to  Josh Scandlen
July 15, 2022 8:14 am

I’m still waiting for the remaining 65 sexes to be identified or is it just Homo Sapiens that have 67 different sexes?

Tim from Montana
Reply to  Bryan A
July 15, 2022 9:19 am

You do not want to see the videos of any of that.

Reply to  Bryan A
July 15, 2022 9:40 am

No, that’s 67 genders – malware, not hardware…

July 15, 2022 8:09 am

Life finds a way

When will these people get that?

Reply to  fretslider
July 15, 2022 2:07 pm

Considering what happened with ice and oceans very recently, both in the evolution of geology and life, large changes are very common and these beasties must have seen much greater changes many times before. They survived, they will continue to survive.

July 15, 2022 8:39 am

I don’t understand epistasis, and it may well be that they’ve discovered something interesting in the field of genetics. But, w/r/t the climate scare, it seems banal.

When meltwater is added to the oceans, they become slightly less salty, of course, because meltwater is fresh. But you’d have to be remarkably silly to fret that the very, very slight change in ocean salinity due to modern climate change could threaten marine life, if you know that marine life withstood repeated glaciations and deglaciations in which sea-levels fell and rose an estimated 400 feet.

J. R.
Reply to  Dave Burton
July 15, 2022 8:47 pm

You forget: the past doesn’t matter. Only the terrifying, threatening future matters.

Reply to  Dave Burton
July 17, 2022 3:21 pm

I believe it’s critical. The claim is that the changes caused by humans are unprecedented, so there would be no reason for creatures to be able to adapt that quickly. The fact they already have this ability is more evidence that any current changes have been experienced before.

July 15, 2022 9:08 am

Climate change is a primary evolutionary driver of resilient species. Eco-idiots like to project their woke fragility onto the relentless force which is nature.

Julian Flood
July 15, 2022 9:15 am

Presumably they consume phytoplankton. If their prey changes – for example if an increase in dissolved silica run-off leads to a bloom in diatoms compared to calcareous types – do the copepod evolve or do other species become dominant?

Let’s speculate. Mechanised agriculture increased during the 20th century. More dissolved silica in the waters around the Newfoundland Banks. Phytoplankton ecology changes to match. Different species of copepod which don’t match the needs of cod fry take over.

Cod population, already under pressure from over-fishing, crashes and refuses to recover.


Ron Long
July 15, 2022 10:02 am

“National Biodefense Analysis and Countermeasures Center” has quite a ring to it. Sounds like a spin-off from Earth First. Shirley they mean no harm.

Bryan A
Reply to  Ron Long
July 15, 2022 11:08 am

They do mean harm but keep calling them Shirley

Coeur de Lion
July 15, 2022 10:50 am

How lucky we are that salinity and precipitation are not changing appreciably.

Captain climate
July 15, 2022 11:04 am

The idea that the ocean will get any fresher in ways that would matter is patently insane.

Gary Pearse
July 15, 2022 11:11 am

Several years ago, a prominent (Australian? – it was posted here on WUWT) oceanographer researcher wrote a paper advising that virtually all lab tank experiments he has reviewed are poorly designed and poorly carried out. They are necessarily ceteris paribus experiments (change salinity, say, and all other things held equal). This assumes that there is no interaction between these creatures and the myriad other creatures, plants, chemical and physical components.

Also researchers shoehorn the experimental time component to fit budget/time constraints – end of fiscal year, graduation timing … all such experiments therefore have too steep a change gradient and too short a time.

Climate and evolution are slow paced. Most also wiped out their subject species by testing ‘conditions’ arising from the impossible RCP 8.5 scenario (i.e. pouring HCL into the tank for ocean acidification experiments.)

One MUST do in-ocean parallel tests over time to examine variability in chemistry, and living elements and real rates of change (like the 50yr Harvard Forest experiment). The Wisconsin copepods experiments killed off 10 if 14 populations. I’d bet money more of these pops would survive if they even stretched out the time for the experiment.

Julian Flood
Reply to  Gary Pearse
July 15, 2022 10:21 pm

It would be interesting to treat the whole ocean ecology as a single entity reacting to changes in its environment and model that. . From that viewpoint Oceana, the vast creature that is the agglomeration of all ocean life and is most of life on our planet, is obviously able to cope with major changes.

Lovelock was wrong. Its not Gaia that rules, it’s Oceana, predapted by billions of years of trial to cope with anything the environment can throw at her.


Philip CM
July 15, 2022 12:13 pm

I could understand the need for such a study if the Copepods were not already “climatized” to the ever-altering salinity of inshore waters. Their natural habitat.

Reply to  Philip CM
July 15, 2022 2:12 pm

Perhaps you hit upon the reason for the study: nature shows by example that they could almost certainly find something to report, thus they could add a “published” to their scorecard.

July 15, 2022 2:06 pm

Freshwater, estuarine and marine copepods have existed for hundreds of millions of years.

This is a nice heroic in vitro study of evolution genetic mechanics, regarding salinity, but with zero implications for climate or biosphere.

Joe Dun
July 15, 2022 4:04 pm

Sounds like the pre-programmed ability to “evolve” that was recently found in Darwin’s finches. In a few generations, they can change their beak length to whatever is needed for the current conditions\. The proposed mechanism for the finches, is the so-called “junk DNA” that has turned out to be regulatory genes.

Jane Michaels
Reply to  Joe Dun
July 16, 2022 5:06 am

So it’s just a population shift and not real positive mutation?

I hate it when evolutionary biologists pull a “shifty” and claim something to be evolution that’s not

Steve Downs
July 16, 2022 5:28 am

So when will proof that CO2 causes catastrophic climate change be revealed? Still waiting 30 years later.

July 16, 2022 7:34 am

Similar phenomenon was seen in fish in the Hudson River that adapted to becoming essentially immune to the damage effects of PCVs over the period of only 20 to 50 generations.

July 18, 2022 8:29 am

Nature finds a way.

%d bloggers like this:
Verified by MonsterInsights