Study confirms truth behind 'Darwin's moth'

Study confirms truth behind 'Darwin's moth'
Peppered moth specimens in a museum. Credit: Olivia Walton

Scientists have revisited—and confirmed—one of the most famous textbook examples of evolution in action.

They showed that differences in the survival of pale and dark forms of the peppered moth (Biston betularia) are explained by how well camouflaged the moths are to birds in clean and polluted woodland.

"Industrial melanism—the prevalence of darker varieties of animals in polluted areas—and the peppered moth provided a crucial early example supporting Darwin's theory of evolution by , and has been a battleground between evolutionary biologists and creationists for decades.

The common pale form of the moth is camouflaged against lichen growing on tree bark. During the Industrial Revolution—when pollution killed lichen and bark was darkened by soot—a darker-winged form emerged in the UK.

Later, clean air legislation reduced soot levels and allowed lichen to recover—causing a resurgence of pale peppered moths.

The example has been well supported by many studies, but nobody had ever tested how well camouflaged the moths were to the vision of their key predators—birds—and how their camouflage directly influenced survival.

Now scientists at the University of Exeter have shown that, to the vision of birds, pale moths are indeed more camouflaged against lichen-covered trees than dark moths—making pale moths less likely to be eaten by birds in unpolluted woodland and giving them an evolutionary advantage.

"This is one of the most iconic examples of evolution, used in biology textbooks around the world, yet fiercely attacked by creationists seeking to discredit evolution," said Professor Martin Stevens, of the Centre for Ecology and Conservation on the University of Exeter's Penryn Campus in Cornwall.

"Remarkably, no previous study has quantified the camouflage of peppered moths, or related this to survival against predators in controlled experiments.

"Using digital image analysis to simulate bird vision and field experiments in British woodland, we compared how easily birds can see pale and darker moths, and ultimately determine their predation risk.

Study confirms truth behind 'Darwin's moth'
Artificial moth used in the field experiment. Credit: Olivia Walton
"Our findings confirm the conventional story put forward by early evolutionary biologists—that changes in the frequency of dark and pale peppered moths were driven by changes in pollution and camouflage."

Most birds can perceive ultraviolet light—invisible to human eyes—and see a greater range of colours than humans, and the Exeter scientists analysed how well pale and dark moths matched lichen-covered and plain , as seen by birds.

To do this, they used museum specimens including some from the collections of Bernard Kettlewell, who conducted famous research on the evolution of the species in the 1950s.

The researchers also created artificial moths, baited them with food and observed predation rates in UK woodland, mostly in Cornwall.

"Through a bird's eyes, the pale peppered moths more closely match lichen-covered bark, whereas darker individuals more closely match plain bark," said first author Olivia Walton, who conducted the research as part of her master's degree at Exeter.

"Crucially, this translates into a strong survival advantage; the lighter moths are much less likely to be seen by wild birds when on lichen-covered backgrounds, in comparison to dark moths."

In the experiment using artificial moths, lighter models had a 21% higher chance of "surviving" (not being eaten by birds).

"We provide strong direct evidence that the frequency of the peppered moth forms stems from differences in camouflage and avian predation, providing key support for this iconic example of natural selection," Professor Stevens said.

The research was funded by the Biotechnology and Biological Sciences Research Council (BBSRC).

The paper, published in the journal Communications Biology, is entitled: "Avian vision models and field experiments determine the survival value of peppered camouflage."

The that most commonly eat peppered moths include sparrows, great tits, blue tits, robins and blackbirds.


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More information: Olivia C. Walton et al, Avian vision models and field experiments determine the survival value of peppered moth camouflage, Communications Biology (2018). DOI: 10.1038/s42003-018-0126-3
Citation: Study confirms truth behind 'Darwin's moth' (2018, August 17) retrieved 24 May 2019 from https://phys.org/news/2018-08-truth-darwin-moth.html
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Aug 17, 2018
Why leave it to nature alone for evolving changes? Why not we too indulge in the act of bringing about changes in animals that we do not eat? These Moths, we should care less for them...whether they are there or gone forever. We now have techniques such as gene-editing, a fine tool !
So many types of birds, frogs, dogs...what not.

Aug 17, 2018
@betterexists, what point are you making?

btw how would creationists argue against the peppered moth, as it seems pretty straightforward.

Aug 17, 2018
"...as it seems pretty straightforward."

Well, some claim that it was a hoax, and those moths were all stuck to the trees. Others, that such 'micro-evolution' "Does not count". IIRC, there are several more arguments, but their convoluted illogic defies rational discussion...

Aug 17, 2018
Not a new species, but a variety. And it reverted back when the pollution stopped.

There are examples of speciation and we should make them better known.

Aug 17, 2018
@someone11235813 I don't think Creationists would have any problem with moths changing their wing colors based upon such selection pressures. Their contention would be that this sort of change is always neutral or downwards with respect to the gene pool, and that random mutation and/or natural selection can never create the new genetic information that would be needed to change one species into another.

Aug 17, 2018
What I never understood about the creationist / eugenics / lysenkoist belief systems is how they reconcile the existence of chaotic-driven genetic code with their religious doctrines and racist dogma?

Aug 17, 2018
This is not "evolution", it's genetic radiation. A species of animal with a wide ranging pre-existing genome is in an environment that favors one specific form. That phase of the species predominates. But the animal does not "evolve". Because, among other things, the specific form can mate successfully with the previous form. Too, if the environment changes, back the animal returns to its exact species form, which is all but impossible under "evolution".
"Speciation" is the eminent test of "evolution". Changes to favor pre-existing genomes could have been and likely were posited by earlier biologists, even those who accepted "creationism"! Darwin even titled his book "The Origin of Species" to indicate the importance of "speciation".
It looks very much like, with no evidence of "speciation" occurring, "evolutionists" are grasping at straws to claim "evolution" is real.

Aug 17, 2018
@veryworried, OK but that's simply saying that creationists simply deny anything no matter how ludicrous. I guess that's why the religious right have an affinity for Trump.

yep
Aug 18, 2018
It looks very much like, with no evidence of "speciation" occurring, "evolutionists" are grasping at straws to claim "evolution" is real.

Are you f*cking daft this isn't the 19th century. We've speciated fruit flys in 35 generations. Do you even read anything about evolution? You need to catch up. Evolution has been proven out in multiple fields from microbiology to paleontology.

Aug 18, 2018
This is not "evolution", it's genetic radiation....
julianpenrod

This is gibberish.
What the hell does "genetic radiation" mean?
You think genes are a kind of 'radiation'?
They can be detected with a geiger counter?


Aug 18, 2018
Because, among other things, the specific form can mate successfully with the previous form.


The question of speciation and mating isn't whether the creature can, but whether it will mate with the other forms. A species starts to separate when mating is prevented by environmental or biological selection.

For example, black moths selecting black moths to mate with, because those that select white moths produce offspring which has lower survivability because of the mixed color. Eventually, this leads to populations where white moths mate with white moths and prefer light colored trees to hang on, and black moths that mate with black moths and hang out on dark bark. The populations become biologically and environmentally separated, and while they -can- interbreed they gradually reduce interbreeding until they act like separate species.

When they act like separate species, the further genetic changes drive them to be different species.

Aug 18, 2018
That's basic darwinian evolution. When you have two niches, white trees and dark trees, and two variants of the same moth which have a survival advantage in either of those two niches, an "interbreed" between the two variants has a survival disadvantage in both niches.

Eventually they have to separate, because if they keep mating with each other the mixed offspring get eaten. A selection pressure exists to stop interbreeding, and when interbreeding becomes rare, they are considered first a subspecies, and when other evolutionary differences between the populations accumulate to the point where they no longer can interbreed, they become a fully separate species.

Many species can technically interbreed, but won't. Yet others can interbreed in a "ring" where the offspring can mate with yet another species successfully, but again won't because of selection pressures not favoring the hybrids. The big cats for example are known for this effect.

Aug 18, 2018
With respect to humy's reply, "radiation" doesn't apply only to atomic decay. "radiation" means to move outward from a source, as in solar radiation. Genetic radiation is a term that means a population leaving a particular general genetic makeup and going to another. In the case of moth populations changing color that means one color predominating almost universally. They are the same moths, they can mate successfully, given time in another environment they will go back to where they were.
And, no, they did not "speciate" fruit flies. They did the same as with the moths perhaps, but they never produced a new species of fruit fly.

Aug 18, 2018
With respect to Eikka's statement, does Eikka really think that two moths, one all black, one peppered, will necessarily produce offspring with a "mixed color"? Traditional genetics indicates the result of a mating is one or the other.
And, no, it is not a matter of one not choosing to mate with the other. Among other things, pheromones will drive moths even of one color to mate with those of the other. Their pheromones didn't change, just the general color of the population!
The essence of the assertion about mating is that genetically, two different species cannot produce offspring that can live and reproduce true, producing more of the same. Different species have gene makeups that don't match so well. That is a defining quality. Horses can mate with donkeys, but any viable offspring is a mule, but they don't necessarily breed true.

Aug 18, 2018
@veryworried, OK but that's simply saying that creationists simply deny anything no matter how ludicrous. I guess that's why the religious right have an affinity for Trump.


and murdering communists love Obama. I get it .

Aug 18, 2018
Genetic radiation is a term that means a population leaving a particular general genetic makeup and going to another.
julianpenrod

That would make it an idiotically redundant term because why not just call that "genetic change" or "genetic evolution" etc?
For this reason, its not a term normally (if ever) used by evolutionary biologists.


Aug 18, 2018
In the case of moth populations changing color that means one color predominating almost universally. They are the same moths, they can mate successfully, given time in another environment they will go back to where they were.
julianpenrod

Yes, and in both directions microevolution is confirmed as that IS microevolution.
And macroevolution that leads to species change is just a series of microevolution events.
If a small change can occur over a relatively short time period then, logically, a series of such changes can make a big change can occur over a relatively long time period. What part of that do you choose to be confused about?
Using your same idiotic 'logic', the tiny daily incremental changes that occur to someone during childhood cannot ever lead to that person becoming an adult because each day the biological characteristics he has are only tiny trivially different from the biological characteristics he had yesterday.

Aug 18, 2018
Well shootinownfoot. Since you altrightfairytails embrace the Global Fascist Axis of your fuhrer Putin the Pimp and his stable of whores with trumpenella and pfenning.

And oppose the Constitutionally legitimate elections of the Presidency of Barak Obama. With your litany of treasonous actions to destroy the independence and liberties of the United States and other Democracies.

You are a quisling, a copperhead apostate who have disavowed your sacred oath of loyalty to the Federal Union and the Constitution.

And sibce you insist that opposing your cadre of evil is defined as "communism"?

Well hurrah for communism and the Rise of the People to cast off the chains of fascism's "Peculiar Institution"!

Aug 18, 2018
As example of the "many studies", here is one where a group finish a work started by Majerus, a critic of Kettlewell's original 1950 experiment, which showed that selection was indeed at work:

Here is one where they found the one loci mutation: Ironically it is one result that shows the creationist talking points more wrong than usual, since it is a large scale insertion of a mobile transposable element, with lots of raw genetic information. It is also recent (early 19th century), not 4 billion years old.

@julianpenrod: This is evolution, which is the process that we know result in speciation if the populations are isolated long enough. But on "mixed color" part, that depends on the allele as in basic Mendelian fashion, the mutation can be dominant, recessive, neither or more rare outcomes.

Aug 18, 2018
{ctd]

As it happens, the carbonaria (black form) allele is dominant over the typica (mottled form)..

Also, the spam filter no longer accepts link references.

1st reference: "Why Evolution Is True" blog by speciation specialist Jerry Coyne, article: "The peppered moth story is solid".

2nd reference: Same blog, article "Peppered moth mutation discovered at last".

Aug 19, 2018
Also, the spam filter no longer accepts link references.

Huh? I was able to post a link.

Aug 19, 2018
@rrwillsj

You silly boy!! Shouldn't you be outdoors climbing trees, jumping in mud puddles and mutilating frogs and cats? It must be almost time for you to move out of your mom's basement and make a space for yourself in her attic. Don't forget your favorite jammies to wear over your big boy Huggies.

Aug 19, 2018
To those who were never aware - not all Creationists have rejected Evolution. We are not all 'Jellicles, you know. Most of us are aware that changes and adaptive measures/features are taken by most any specie to survive the natural order. Predation is natural to all or most species, and if not for the ability to evolve, most Life Forms would have perished.
A good example is the chameleon, and other creatures that change color quickly to blend with surroundings. However, humans have no such ability to change in the same manner. Instead, humans have evolved a brain that is capable of quick decisions to enable survival. It isn't a foolproof ability, but then, we're only human.
:)

Aug 19, 2018
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Aug 19, 2018
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Aug 19, 2018
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Aug 19, 2018
Just the article title "Study confirms truth behind 'Darwin's moth'" makes me upset. What the "truth" is supposed to mean? Truth is propagandist word - not scientific word.
Whart1984

"truth" is a common English word and just because it has no formal scientific definition doesn't mean it cannot correspond to any reality. The word "God" also has no formal scientific definition; so there is no God? -your logic.
The science shouldn't recognize any "truths" - only theories and their logical arguments.
WRONG. It should recognize ALL these things INCLUDING the truths of the proven scientific facts, such as round Earth etc.
It should always remain open to all alternatives.
ONLY where and when there are credible alternatives. There are NO credible alternatives to either evolution or the Earth being round and not flat etc.


Aug 19, 2018
--continued---

And please note, that Darwin's theory is not about adaptation - but about species formation.
NO, it is about BOTH. The theory obviously doesn't exclude microevolution; why would it? After all, macroevolution is just a series of microevolution events thus it wouldn't make any sense for the theory to exclude it!
The adaptation would actually contradict the formation of new species, because it would remove the main reason for their formation.
Your above assertion makes no sense. The only 'reason' is/involves evolution. Perhaps you think evolution theory says there is some other kind of 'reason'? If so, what? Perhaps you think this 'reason' implies 'purpose'? If so, you haven't understood the theory.

Aug 19, 2018
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Aug 19, 2018
With respect to Eikka's statement, does Eikka really think that two moths, one all black, one peppered, will necessarily produce offspring with a "mixed color"? Traditional genetics indicates the result of a mating is one or the other.


Not necessarily, but the effect is the same.

There are two things to select for: where the moths prefer to habitate, and what their color is. The offspring of black and white moths can be black, white, or a mix of black and white, and they can prefer dark trees, white trees, or be indifferent about the trees.

Either ways, the offspring of the mixed mating have a greater probability of ending up white-on-black or being of intermediate color which suits neither niche, which means a greater part of the population ends up ill-fit for their environment.

When all three, black, white, mixed, moths multiply through reproduction, it doesn't take a big disadvantage for the mixed variant to vanish because reproduction is exponential.

Aug 19, 2018
Small persistent disadvantages or advantages in evolution lead to rapid shifts in populations, because the difference between two exponential functions is also exponential.

Take two functions, 1.01^x and 1.02^x. The difference between the results at x=1 is about 1% whereas the difference a hundred "generations" later is 268% in favor of the greater function. That's to say, after a hundred years, a ~1% advantage in reproduction for one type of moth changes the population from a 1:1 situation closer to 1:3. In evolutionary timescales, this is a blink of an eye.

After 200 years, the situation is about 1:7 and the disadvantaged type of moth is well on the way to becoming extinct, whereas the black moths that mate with black moths and live on black trees, and white moths that mate with white moths and live on white trees, are becoming separated as species because they refuse to interbreed.

Aug 19, 2018
If so, you haven't understood the theory
Try to explain first, how the fact that lighter moths had a 21% higher chance of "surviving" (not being eaten by birds) support the "truth" of Darwinian based "explanation", that moths get darker because of industrial pollution -
Whart1984

You completely misunderstand what this article is suggesting. The new evidence merely confirms an old theory of EXACT DETAILS of HOW specifically those moths evolved, NOT that they merely DID evolve (i.e. ignoring all details of EXACTLY HOW so) because that was never in real question given the overwhelming evidence for microevolution.
It merely confirmed that it happened specifically via industrial pollution rather than via some other alternative evolutionary process i.e. by a process NOT directly involving specifically industrial pollution in particular.


Aug 19, 2018
Once the moths have separated into subspecies like that, further changes take place due to the differences in their environments. Different types of flowers may be present around dark trees vs. white trees, so their mouths evolve into different shapes to better suit the flowers - just like Darwin's finches.

At that point, while it would be genetically possible to produce a hybrid, the offspring are no longer viable because they're most likely malformed, physically and behaviourally. It's no longer possible to argue that they're the "same moth".

And that's how "microevolution" turns to "macroevolution" - the separation of species.

You can argue that the mouth shapes, colors, mating preference, environmental preference, etc. were all present in an earlier "proto-moth" and simply got dropped out along the way, but this does not invalidate the speciation process. It works either way, and that question is a different argument that can be tested by other means.

Aug 19, 2018
In fact, the "baramin" argument would require that all animals start out with an incredibly large and complex genome to include all the possible future variants, but carrying such a large genome is a disadvantage because it has to be replicated at a great cost, and the offspring of such genomes would be genetic mad-libs and most of them would die right away, so the "prototypes" would be eliminated very early on in the process of life.

And with the baramins dead and gone, you'd have the problem of explaining why new species still keep popping up even though the prototypes are long gone. Something else must contribute to add new genetic information, so the process of selection can continue.

Aug 19, 2018
You completely misunderstand what this article is suggesting. The new evidence merely confirms an old theory of EXACT DETAILS of HOW specifically those moths evolved, ...
It merely confirmed that it happened specifically via industrial pollution rather than via some other alternative evolutionary process i.e. by a process NOT directly involving specifically industrial pollution in particular.
I should also add to that;
Even if the evidence hypothetically was different from what it was and actually contradicted the theory that the moth evolution happened specifically directly via industrial pollution but rather was caused by some other evolutionary process, that wouldn't contradict the theory of evolution (in its generic form) but rather merely mean we would have change our theory of exactly HOW that moth species evolved, that is all. It STILL couldn't make us rationally conclude it didn't evolve! That is because that part was never in doubt.


Aug 19, 2018
humy's posts are all doggerel.
"Genetic radiation" relates to entire populations and, in those populations, the total genome remains the same, but the expression of phases changes. No genes change at all. And calling it "microevolution" or "macroevolution" doesn't "change" it, it would still be "evolution". But the fundamental demonstration of "evolution" is speciation, that's why Darwin entitled his book, "The Origin of Species".
And, face it, if you have a hundred separate cases of genetic radiation in a population of moths, they are still all of the same species. They may have genes combinations never before seen all in one individual but absolutely none of those changes is a mutation! The moths from one population can still successfully mate with original moths and produce offspring that breed true.
"Microevolution" and such sound like specious terms to dodge the issue that speciation has never occurred.

Aug 19, 2018
the total genome remains the same,..No genes change at all.
julianpenrod

False. This is because there exists these pesty things called 'mutations'. The gene mutation for dark moth wings being just one example.
But the fundamental demonstration of "evolution" is speciation,
False. It is both microevolution and macroevolution and, given macroevolution is just a long series of microevolution events, it wouldn't make any sense to claim the contrary (like you do).
The moths from one population can still successfully mate with original moths and produce offspring that breed true.
That is part of the reason why microevolution is called microevolution and not macroevolution; What about it? Are you desperately trying to confuse the issue by equating the two?

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