Evolution Doesn't Always Take Millions of Years
How about 20 generations over an 8 year time frame!?
When Evolution Is Not So Slow And Gradual
ScienceDaily (June 3, 2009)
What's the secret to surviving during times of environmental change? Evolve…quickly.
Adapted from materials provided by University of Chicago Press Journals.
A new article in The American Naturalist finds that guppy populations introduced into new habitats developed new and advantageous traits in just a few years. This is one of only a few studies to look at adaptation and survival in a wild population.
A research team led by Swanne Pamela Gordon from the University of California, Riverside studied 200 guppies that had been taken from the Yarra River in Trinidad and introduced into two different environments in the nearby Damier River, which previously had no guppies. One Damier environment was predator-free. The other contained fish that occasionally snack on guppies.
Eight years after their introduction, the team revisited the Damier guppies to see what adaptive changes they might have picked up in their new environments. The researchers found that the females had altered their reproductive effort to match their surroundings. In the environment where predators were present, females produced more embryos each reproductive cycle. This makes sense because where predators abound, one might not get a second chance to reproduce. In less dangerous waters, females produced fewer embryos each time, thus expending fewer resources on reproduction.
Finally, the researchers wanted to see if these adaptive changes actually helped the new population to survive. So they took more guppies from the Yarra, marked them, and put them in the Damier alongside the ones that had been there for eight years. They found that the adapted guppies had a significant survival advantage over the more recently introduced group.
In particular, juveniles from the adapted population had a 54 to 59 percent increase in survival rate over those from the newly introduced group. In the long run, survival of juveniles is crucial to the survival of the population, the researchers say.
The fact that fitness differences were found after only eight years shows just how fast evolution can work—for short-lived species anyway.
"The changes in survival in our study may initially seem encouraging from a conservation perspective," the authors write. "[B]ut it is important to remember that the elapsed time frame was 13-26 guppy generations. The current results may therefore provide little solace for biologists and managers concerned with longer-lived species."
When Evolution Is Not So Slow And Gradual
ScienceDaily (June 3, 2009)
What's the secret to surviving during times of environmental change? Evolve…quickly.
Adapted from materials provided by University of Chicago Press Journals.
A new article in The American Naturalist finds that guppy populations introduced into new habitats developed new and advantageous traits in just a few years. This is one of only a few studies to look at adaptation and survival in a wild population.A research team led by Swanne Pamela Gordon from the University of California, Riverside studied 200 guppies that had been taken from the Yarra River in Trinidad and introduced into two different environments in the nearby Damier River, which previously had no guppies. One Damier environment was predator-free. The other contained fish that occasionally snack on guppies.
Eight years after their introduction, the team revisited the Damier guppies to see what adaptive changes they might have picked up in their new environments. The researchers found that the females had altered their reproductive effort to match their surroundings. In the environment where predators were present, females produced more embryos each reproductive cycle. This makes sense because where predators abound, one might not get a second chance to reproduce. In less dangerous waters, females produced fewer embryos each time, thus expending fewer resources on reproduction.
Finally, the researchers wanted to see if these adaptive changes actually helped the new population to survive. So they took more guppies from the Yarra, marked them, and put them in the Damier alongside the ones that had been there for eight years. They found that the adapted guppies had a significant survival advantage over the more recently introduced group.
In particular, juveniles from the adapted population had a 54 to 59 percent increase in survival rate over those from the newly introduced group. In the long run, survival of juveniles is crucial to the survival of the population, the researchers say.
The fact that fitness differences were found after only eight years shows just how fast evolution can work—for short-lived species anyway.
"The changes in survival in our study may initially seem encouraging from a conservation perspective," the authors write. "[B]ut it is important to remember that the elapsed time frame was 13-26 guppy generations. The current results may therefore provide little solace for biologists and managers concerned with longer-lived species."
Replies to This Discussion
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Permalink Reply by Nelson on -
i saw this on Science Daily. so cool! thanks for posting it here Johnny! so i guess this whole "evolution" thing is really really real huh? :P
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Permalink Reply by Matthew on -
Does anyone know if the guppies evolved enough to be considered new species? Or was it just the change in reproductive habits?
Not that changing reproductive habits isn't evolution. Just that some would argue (not me) that a change in reproductive habits is "microevolution" (*shudder) or "just an adaptation, but not evolution" (*grrrrr).
As an aside...how does one mark a guppy and then find it again? Radioactive isotopes, perhaps?
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Permalink Reply by Johnny on -
Yea, I thought about noting that creationists will just say its "micro-evolution," but left it out.
I wondered the same thing... Could the two still cross breed? If they can't, then the "micro" claim couldn't be used. If they can, then it would be interesting to see how many generations it takes for natural selection to re-establish the entire population being the ones producing more eggs.
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Permalink Reply by Pitabred on -
There is no defined species line. Even interbreeding isn't a great metric... are breeds of dogs different species? A male mastiff can't breed with a chihuahua successfully. Lions and tigers can create tigons and ligers, and those aren't always sterile. What about bird species such as various Galapagos finches that simply don't interbreed, even if they are genetically capable of it? Don't fall for the creationist line falsely differentiating micro- from macro-evolution. There is no hard and fast line between species, there is no line they can point to where they stop "believing" in evolution.
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Permalink Reply by Nelson on
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but surely you'd agree that whether or not populations of closely related animals interbreed is a commonly used arbiter when deciding whether or not a population is a different species? that it's not perfect i agree with but it's very important to taxonomists.
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Permalink Reply by Matthew on
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This is a good point, though I've found it difficult to explain to those who do not understand evolution.
Also, as Napoleon Dynamite said: "Ligers are pretty much my favorite animal. It's like a lion and a tiger mixed... bred for its skills in magic." - Attachments:
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liger0505.jpg, 35 KB
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Permalink Reply by Johnny on
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Yea, I cringe at the thought of throwing in micro/macro because they aren't real scientific terms; but it is a battle we often have to fight (so I throw it in sometimes as a preemptive strike).
Also you're right (and others that posted) on the speciation technicalities; I just threw out the first two hypotheses that popped into my head. For speciation, Nelson's comment seems most pertinent; that its not a matter of if they can crossbreed, but do they crossbreed.
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Permalink Reply by Laura on -
Bedazzled guppy collars? Permanent marker? Iris recognition / fin printing? Painstaking individual training whereby each guppy learns to respond to its name when called?
If I were a scientist, those are the possibilities I'd consider.
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Permalink Reply by Matthew on
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You forgot....um. um.
Well how about that, I can't come up with anything else.
Nicely played, ma'am.
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Permalink Reply by Nelson on
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a species is generally considered a new species if it's range, habitat, or physiology make it so that it doesn't mate with closely related populations. for instance, though the aquatic iguanas on the Galapagos could certainly reproduce with their terrestrial cousins on the mainland, they are both considered separate species. though the long-beaked and short-beaked common dolphins have areas of overlap in their range, the two populations do not mate with members of the other group and so they are considered separate species. though a horse and a donkey can mate they won't usually given the option of members of their own species and indeed the resulting union of a male donkey and a female horse, a mule, is sterile and so they are physiologically unable to continue the line.
so the answer to your question is found in whether or not the two populations of guppy mate with each other when introduced or if they continue only to mate with members of their own population.
good question about marking the guppies. i don't know the answer to that one. i would think radioactive isotopes would be dangerous to the individual fish and that if it were to be strong enough to be able to be picked up by a sensor it would be very dangerous indeed to the individual fish. if they would have to catch the fish in a net and scan them for a radioactive isotope marker it would seem easiest to simply tattoo the fish with an indelible ink and simply visually verify the presence of the marker that way. not to mention, even if the radioactive isotope wasn't dangerous to the fish, it would still risk messing with natural rates of mutation and so would be considered a confounding variable.
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