From yeast, researchers learn how populations collapse

Jun 01, 2012 by Anne Trafton
Yeast colonies shown close up. Image: wikimedia commons/Lilly M.

In the early 1990s, overfishing led to the collapse of one of the most bountiful cod fisheries in the world, off the coast of Newfoundland. Twenty years later, the cod population still has not recovered, dramatically affecting the economic life of the region.

To explain this kind of collapse, ecologists have long theorized that populations suffering a in (such as overfishing) appear stable until they reach a tipping point where the population plummets. Recovery from such collapses is nearly impossible.

“This is thought to underlie lots of sudden transitions — in populations, ecosystems or climate regime shifts,” says Jeff Gore, an assistant professor of physics at MIT.

Gore and his students have now offered the first experimental validation of this theory. They showed that in populations of yeast subject to increasingly stressful conditions, populations became less and less resilient to new disturbances until they reached a tipping point at which any small disruption could wipe out a population.

“In the wild, you do see things change suddenly, and this model is a reasonable explanation, but it’s very hard to prove that this is happening,” Gore says. “This is the kind of thing we can do in the laboratory that you can’t do in the wild.”

The findings, published in the June 1 issue of Science, could help fishery and wildlife managers identify so interventions can be made before total collapse occurs. Lead authors of the paper are MIT graduate student Lei Dai and visiting student Daan Vorselen. Postdoc Kirill Korolev is also an author.

Stress response

Gore and his co-authors did their experiments with populations of yeast growing in test tubes. Each of the organisms secretes an enzyme that breaks down sucrose in the environment into smaller sugars that it can use as a food source. All of the yeast benefit from this process, so the population is most successful when it maintains a certain density — not too low, not too high. 

This phenomenon, known as the “strong Allee effect,” occurs whenever members of a population profit from having other individuals nearby. For example, fish benefit from traveling in a school, which offers protection from predators. The theoretical model tested in this paper should hold true for any population that shows a strong Allee effect.

In this study, the researchers simulated a decline in environmental conditions by removing a certain percentage of each yeast population from its test tube every day, representing the populations’ death rate. In real life, such deteriorating conditions could result from lack of food, overfishing, climate change, acidification of the ocean or anything else detrimental to a population.

The researchers found that as conditions decline, the population becomes less resilient. Whenever it suffers any kind of perturbation, the population is more prone to extinction, requiring more time to recover to a stable population size.

In this case, the disturbance was a salt shock, which disrupts many cellular functions in yeast and can lead to death. Populations that were closer to the tipping point collapsed, while those living in better environmental conditions were able to bounce back. “In the more challenging environments, the populations are not as robust,” Gore says. “Moreover, it is often difficult to predict an upcoming collapse by simply monitoring the decrease in population size.”

But there is cause for some optimism: The researchers found that the fluctuations in yeast population became larger and slower near the tipping point. Thus, an increase in size and timescale of fluctuations may serve as indicators of how fragile a population is and provide advance warning of its impending .

Stephen Carpenter, a professor of zoology at the University of Wisconsin at Madison, says the new study’s biggest contribution is that the researchers were able to both map the location of the tipping point, or threshold, and measure the early warning signs that predict it.

“Many systems are so complicated that you can’t really measure resilience,” he says. “You might be pretty sure that there’s a threshold, and you can move from one side to the other, but you don’t know exactly where the threshold is.”

In the wild

While this phenomenon is easier to observe in a laboratory than in wild populations, the researchers believe that the warning signs they have identified — most importantly, the loss of resilience as the tipping point is approached — could help wildlife and fishery managers monitor their populations.

This could be achieved by measuring population levels and comparing them with the fluctuations predicted by the researchers’ model. The team is also studying the spatial patterns of populations as they decline, in hopes of identifying warning signs that might be easier to monitor than fluctuations.

The researchers are also looking at more complex systems to see if they can find the same effect.

“This is the simplest case you could possibly imagine — a single species in a test tube. We’re interested in trying to start adding a second species, or at least a second strain ... to see if the same dynamics will be there,” Gore says.

Explore further: Dwindling wind may tip predator-prey balance

Related Stories

Marine scientist discusses cod colonization

May 24, 2012

New evidence suggests that Atlantic cod may have the ability to affect entire food webs in both benthic and pelagic marine ecosystems, according to a University of Maine marine scientist, writing in the Proceedings of ...

Predicting the microbial 'weather'

Apr 17, 2012

New computer models are letting scientists forecast changes in the population of microbes in the English Channel up to a week in advance.

Hybrid possum gives endangered species a chance

May 26, 2011

Australian researchers have successfully bred two genetically distinct Mountain Pygmy-possums, playing a major role in preventing the endangered population in the Victorian Alpine region from further decline.

Recommended for you

Pakistan releases smuggled turtles into the wild

3 hours ago

Pakistani officials and environmentalists on Monday released some 200 rare turtles into the River Indus after the reptiles were retrieved from a southwestern Chinese town where they were seized by customs ...

Big science from small insects

8 hours ago

Anniversaries are often a time to look back. But after taking stock of the past, it can be just as important to look to the future.

Dwindling wind may tip predator-prey balance

Sep 19, 2014

Bent and tossed by the wind, a field of soybean plants presents a challenge for an Asian lady beetle on the hunt for aphids. But what if the air—and the soybeans—were still?

Asian stars enlisted to fight African rhino poaching

Sep 19, 2014

Increasingly desperate South African conversationists are turning to a multi-national team of "rhino ambassadors" to try to end the scourge of poaching—and Vietnamese pop diva Hong Nhung has been recruited ...

User comments : 21

Adjust slider to filter visible comments by rank

Display comments: newest first

bertibus
5 / 5 (1) Jun 01, 2012
Unfortunately, in many cases, such as the fish stocks example given, the problem is less one of science and more one of politics. There was ample warning of the Newfoundland Fisheries situation, but short-sighted pressure from the fishing industry and the subsequent stupidity from local politicians kept the fishery wide open when a relatively short moratorium might have saved the day. Hopefully, this research will make the argument for (self-interested) conservation more powerful, and easier to make.
CapitalismPrevails
2 / 5 (12) Jun 01, 2012
All the more reason to privatize the ocean so fishing boats would be fined for trespassing on private property charged a fee for the right to fish. The private owners would be more concerned about the long term because they would profit more in the long term if the cod fish isn't made instinct. It would probably create more demand for fish farms.
davhaywood
2.9 / 5 (8) Jun 01, 2012
Privatize the ocean? Hahahahahaha! That just made my day. Thanks for the laugh.
MoonSpot
2.6 / 5 (5) Jun 01, 2012
@CapitalismPrevails Wow talk about nightmarish. What's worse is it will probably happen, and shortly there after we'll all get to hear about how regulation is hurting their industry, more corny bailouts for management-owners (aka profit protectionism) and fisherman wage cuts to surf like levels for workers/producers. All the while the reality of corporations continuing to destroy the environment for short term gain.

I for one am not too interested in yet another re-run of "socialism for the rich, capitalism for everyone else". It's just too much of a transparent "1 trick pony"

Whoa wait, this isn't Politics.org grr. But if you apply the "shocks" discussed here to the market, people repeatedly losing their savings I guess it's sociology which is kind of a science...
CapitalismPrevails
2 / 5 (8) Jun 01, 2012
more corny bailouts for management-owners (aka profit protectionism)
Do you call bailouts a form of capitalism? I sure don't. Just get rid of reactionary politics.
and fisherman wage cuts to surf like levels for workers/producers.
Yes and no. If there wasn't a minimum wage, it would be more practical for startups to be established and give workers choices. Therefore, employers would be forced to compete for the talent. Competition=productivity=everyone wins.
CapitalismPrevails
2.5 / 5 (8) Jun 01, 2012
All the while the reality of corporations continuing to destroy the environment for short term gain.
Do ranchers destroy their private property for short term gain? Would a rancher over graze his pasture and expect there not to be a weed infestation leading to less grazable land? Ranchers must be conservationists to the extent that they don't go under the next year or 5 years. The same would apply to corporations if it was their property and the same for fisheries IF they were privatized in some way. Ofcourse, your not going to get perfection but you'll ultimately end up with better results. Everything is a matter of trade-off.

I for one am not too interested in yet another re-run of "socialism for the rich, capitalism for everyone else". It's just too much of a transparent "1 trick pony"
I'm not sure of what your talking about but if government was smaller(e.g. no SEC, EPA, FTC, etc.) the less capacity there would be for corruption.

Cave_Man
2.3 / 5 (6) Jun 01, 2012
more corny bailouts for management-owners (aka profit protectionism)
Do you call bailouts a form of capitalism?


He was obviously saying that the bailouts for banks etc was socialism for the rich while us poor saps get stuck in high interest hell of your so called perfect capitalism.

FFS dude No to all your posts, just no, you really need to be shot into the sun, maybe we can have capitalist bidding to see who will do it the cheapest.... And BTW Capitalism is not prevailing (for the bottom half of us at least), however communist china seems to be doing fairly well.

Government does not need to be smaller you dolt if anything it needs to have much much more regulatory power with more transparency and oversight to match. That way monsanto won't be able to patent your DNA. But you go ahead and play tea party with your imaginary friends.
CapitalismPrevails
2.5 / 5 (8) Jun 02, 2012
He was obviously saying that the bailouts for banks etc was socialism for the rich while us poor saps get stuck in high interest hell of your so called perfect capitalism.
Straw-man argument. Your perception is your reality. Why would banks subject its customers to "high hell interest" and make it more practical for other more ambitions banks to startup and create more competition? Government regulations and taxes create extra costs for corporations/banks and leads to your "high hell interest" because they have to pass their added costs to the customers.
FFS dude....you really need to be shot into the sun....however communist china seems to be doing fairly well.

LMAO, you almost sound as incoherent and militant as VD. Common buddy, everyone knows communist China is far more capitalistic than most western countries w/ 2% growth. What they lack is a relatively uncorrupted court system like ours to protect basic civil and property rights, which are a facade.
Cave_Man
2.4 / 5 (5) Jun 02, 2012
What they lack is a relatively uncorrupted court system like ours to protect basic civil and property rights, which are a facade.


Now sir you have a 100% backwards ass understanding of our current state of "law". The supreme court has shown again and again that they can be bought by corporations, but teabagger LOVE that. Clarence Thomas I believe used to work for Monsanto and once appointed he ruled in favor of Monsanto in a groundbreaking (ie nature-fucking) case which has now resulted in the patenting of 90 % of known seeds as well as well as a good portion of the human genome. Way to go corporate america, if the economy still needs help after the amount of free money, tax breaks and other lobby induced bullcrap that goes on here then it's bound to fail with or without any amount of help.

As for China, they have more than 3X the population, meaning they should be allowed 3X the proportion of problems relative to we the US, from what I've seen they aren't even that.
Cave_Man
2.6 / 5 (5) Jun 02, 2012
One more thing, I typed out a nice long coherent message full of big words and complex sentences but of course I had to misclick on a link and send it off to that void where all the rest of my effort winds up.

I gotta say, out of all the arguing that goes on here I firmly believe that the only thing that can save our country is learn how to get along or at the very least learn to communicate effectively. I think the government should pay for free all access, cross discipline education over the net and locally with real people. I think govt. has no business in the everyday lives of regular people, specifically substances ingested and non-violent activities done on private property. Individual businesses should pay no taxes and receive no help from the govt.

Also our federal govt should not be composed of 10% former monsanto employees and 100% former corporate rich selfish jerks.

But then again i'm pretty zen, if you think for yourself then none of it matters in the long run.
Cave_Man
2.5 / 5 (4) Jun 02, 2012
Straw-man argument. Your perception is your reality. Why would banks subject its customers to "high hell interest" and make it more practical for other more ambitions banks to startup and create more competition? Government regulations and taxes create extra costs for corporations/banks and leads to your "high hell interest" because they have to pass their added costs to the customers.


Logical fallacy using your own (partial)perception as your reality and stated "facts"

Remember when the fed was loaning billions to banks at 0%, what regulations and taxes are you talking about that lead to my high interest cost?

Big banks work together, it's obviously better to collude and make sure that you only need to lower your borrowing interest rate one point below your closest competitor to drive up business. Once you are as big as Chase you could buy up any little banks you want or lobby to make it unfeasible to start a small bank using profit taxes that would do nothing to large banks
CapitalismPrevails
1.6 / 5 (7) Jun 02, 2012
The supreme court has shown again and again that they can be bought by corporations
Just the times when you don't agree with their rulings i bet. But when they rule in favor of your side, that's cool. Apparently you have a grudge against corporations. I'll admit i haven't delved into the ethics of the case but allowing corporations to patent the human genome is unnerving.But what's the government alternative to address these issues? The country can still make a constitutional amendment, ratified by the states, not allowing human DNA to be patented. It's called separation of powers and its a good thing which China doesn't have.
As for China, they have more than 3X the population, meaning they should be allowed 3X the proportion of problems relative to we the US,from what I've seen they aren't even that.
From what you've seen through state controlled media are you implying you want to move there? Be my guest and vote with your feet if you like. I like my 1st & 2nd amendments
CapitalismPrevails
1.7 / 5 (6) Jun 02, 2012
Remember when the fed was loaning billions to banks at 0%, what regulations and taxes are you talking about that lead to my high interest cost?
Hmmm CRA, Dodd Frank bill etc..google it..etc.. maybe? Your not understanding me at all are you? The Federal Reserve is a fourth branch of government in all but name. Mandated by the 1910 Federal Reserve Act but is officially called a corporation but is still government by law. I'm all for abolishing it as congress has the power to regulate money and not a separate institution. Most of our fiscal problems would not exist today if there were no central banks in the world.

It's getting late and i can see i'm making 0% progress with you. It was worth a try i suppose. Have fun blaming corporations first and pursuing life, liberty, and the pursuit of hatefulness.
MoonSpot
3.3 / 5 (3) Jun 02, 2012
employers would be forced to compete for the talent. Competition=productivity=everyone wins.


@CapitalismPrevails Employers forced to compete? Or workers forced to compete even more so employers get top talent at bargain prices.

Your analogy of the rancher not over grazing his property. Although accurate for that instance, the methodology/ideology does not translate for all economic endeavors. Lets say the rancher is a miner, mining ore on government property, in the 3rd world. Tell me if you honesty think that this mining corp/owner would care what state the environment is left in if they don't have to live there afterwards. From illegal use of mercury in gold mines, unknown chemicals used in fracking, to sludge ponds from tarsands development (viewable from space!)

I'm sure that they're examples of Corps that do act responsibly and compassion, but the only ones I can think of only acted b/c it would save them money & later spun the "Because We Care" record.
SatanLover
0.7 / 5 (26) Jun 02, 2012
When we privatize our oceans, they will make deals with oil companies, sell their company of an oil polluted ocean to a company that will turn the ocean into an algae farm.
MoonSpot
1 / 5 (1) Jun 02, 2012
@CapPrecails I think it is important to distinguish between a sole-proprietor and Corps. If we're talking about an individual I can subscribe a bit to the faith you seem to place in them to be honourable, just and responsible custodian's of the social contract in their trade. I cannot however extend that possibility to Corporations and its shareholders. Shareholders may be vaguely aware of the industry they're investing in, but they don't care what the Corp has to do to generate ever greater profit. Shareholders only concern is that they make more and more money for themselves as they're disassociated from the consequences and actions of the Corp.

There are many Libertarian ideals I like in theory, but it relies too much on peoples level of honesty and integrity and makes it far too easy for the unscrupulous to take advantage of others.

you may just have a higher opinion of others then I, but your 1st post screamed(to me) "Repeal Bass-Steagall! Let's party like it's 2008!"
slayerwulfe
not rated yet Jun 02, 2012
dayhaywood China is already privatizing what they consider to be their ocean. this study is flawed because it does not take into account that predators also travel in schools or packs and we are predators. also research may take place in the wild and the blue pike of lake Erie are an example. i submit for your consideration who or what are the predators of yeast and exactly what is this article informing me of.
ka_
5 / 5 (2) Jun 03, 2012
All the more reason to privatize the ocean so fishing boats would be fined for trespassing on private property charged a fee for the right to fish. The private owners would be more concerned about the long term because they would profit more in the long term if the cod fish isn't made instinct. It would probably create more demand for fish farms.


A naive idea, besides, to some extent this is exactly what we do have: Each country have its sovereign sea borders, and do have regulation and policing of those rules in their territory, but:

1) Fish in the sea know no borders
2) If one sea-owner (read country) does not fish the fish while in its waters, it might become the catch for your neighbor, leaving you with no profit nor increased yield in coming years.
3) There are areas no country can claim. Try - get a war
4) it will only get worse by splitting the sea in smaller chunks

So you end up having to negotiate quotas on a Global scale. This is done, but do each country agree..
retrosurf
not rated yet Jun 03, 2012
>All the more reason to privatize the ocean ...

All the more reason to regulate ocean fishing with a single worldwide entity, with the power to enforce regulations by force, for the good of all.

I believe that the oceans are doomed.

Mankind will fish and overfish until there is no edible vertebrate life left in them. And then we'll eat all the squid and jellyfish and krill.
eljo
1 / 5 (1) Jun 03, 2012
Actually, privatizing the ocean is a good idea, as long as you use intransitive property rights and give every human his own idealized equal part of the ocean. Intransitive means you cannot sell it. It would mean you own the fish stocks in your personal area of ocean during your entire life, but not longer. Oceans are a resource that evry human deserves equal ownership of. Each human deserves to have the final word over his idealized fraction of the world and resources. This can be arranged via the habeas area right. If you want to find out more about it google habeasarea dot be. Have a nice day!

slayerwulfe
not rated yet Jun 03, 2012
to eljo i like your attitude but there are faults every human is not necessarily human and only governments are long lasting enough to take control, thanks for the'link'