Scientists reveal driving force behind evolution

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Scientists reveal driving force behind evolution

#1  Postby RichardPrins » Feb 27, 2010 4:23 am

Scientists reveal driving force behind evolution
The team observed viruses as they evolved over hundreds of generations to infect bacteria. They found that when the bacteria could evolve defences, the viruses evolved at a quicker rate and generated greater diversity, compared to situations where the bacteria were unable to adapt to the viral infection.

The study shows, for the first time, that the American evolutionary biologist Leigh Van Valen was correct in his 'Red Queen Hypothesis'. The theory, first put forward in the 1970s, was named after a passage in Lewis Carroll's Through the Looking Glass in which the Red Queen tells Alice, 'It takes all the running you can do to keep in the same place'. This suggested that species were in a constant race for survival and have to continue to evolve new ways of defending themselves throughout time.

Dr Steve Paterson, from the University's School of Biosciences, explains: "Historically, it was assumed that most evolution was driven by a need to adapt to the environment or habitat. The Red Queen Hypothesis challenged this by pointing out that actually most natural selection will arise from co-evolutionary interactions with other species, not from interactions with the environment.

"This suggested that evolutionary change was created by 'tit-for-tat' adaptations by species in constant combat. This theory is widely accepted in the science community, but this is the first time we have been able to show evidence of it in an experiment with living things."

Dr Michael Brockhurst said: "We used fast-evolving viruses so that we could observe hundreds of generations of evolution. We found that for every viral strategy of attack, the bacteria would adapt to defend itself, which triggered an endless cycle of co-evolutionary change. We compared this with evolution against a fixed target, by disabling the bacteria's ability to adapt to the virus.

"These experiments showed us that co-evolutionary interactions between species result in more genetically diverse populations, compared to instances where the host was not able to adapt to the parasite. The virus was also able to evolve twice as quickly when the bacteria were allowed to evolve alongside it."

The team used high-throughput DNA sequencing technology at the Centre for Genomic Research to sequence thousands of virus genomes. The next stage of the research is to understand how co-evolution differs when interacting species help, rather than harm, one another.

The research is published in Nature and was supported by funding from the Natural Environment Research Council (NERC); the Wellcome Trust; the European Research Council and the Leverhulme Trust.
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Re: Scientists reveal driving force behind evolution

#2  Postby DanDare » Feb 27, 2010 5:34 am

That seems to implay an either/or between adaptation to environment vs adaptation to other species. I think its just that environmental changes tend to be slower and less frequent.
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Re: Scientists reveal driving force behind evolution

#3  Postby argumentativealex » Feb 27, 2010 9:18 am

"This suggested that evolutionary change was created by 'tit-for-tat' adaptations by species in constant combat. This theory is widely accepted in the science community, but this is the first time we have been able to show evidence of it in an experiment with living things."


That certainly chimes with the idea that the Cambrian explosion represents the rapid evolution of shells, hard carapaces, eyes etc. as defences against increasingly more sophisticated and better equipped predators. (http://www.fossilmuseum.net/Evolution/T ... msRace.htm - good pics of trilobites)
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Re: Scientists reveal driving force behind evolution

#4  Postby my_wan » Feb 27, 2010 12:51 pm

I always found it strange that a distinction would be made between environment and external biota in the environment. It always seemed obvious to me that other biota in the environment are part and parcel to the environment, thus define what the environment is. The 'Red Queen Hypothesis' seemed to a refutation of an artificial distinction without explicitly rejecting the artificial distinction. Perhaps this experiment could be turned on its head, in the particular biota/environment distinction used. Watch how a population evolves in a constantly changing environment in absentia of competing species.
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Re: Scientists reveal driving force behind evolution

#5  Postby Badger » Feb 27, 2010 1:28 pm

Has there been any work comparing these results with those
from otherwise similar but larger populations?
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Re: Scientists reveal driving force behind evolution

#6  Postby Spearthrower » Feb 27, 2010 2:52 pm

DanDare wrote:That seems to implay an either/or between adaptation to environment vs adaptation to other species. I think its just that environmental changes tend to be slower and less frequent.



I think it's clearer to consider intra- and interspecific conflict as part of the 'environment'.
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Re: Scientists reveal driving force behind evolution

#7  Postby DanDare » Feb 27, 2010 3:14 pm

Spearthrower wrote:
DanDare wrote:That seems to implay an either/or between adaptation to environment vs adaptation to other species. I think its just that environmental changes tend to be slower and less frequent.


I think it's clearer to consider intra- and interspecific conflict as part of the 'environment'.

There is an important difference. Species competing co-evolve. The natural environment, climate, presence of water courses etc. tends to be less reactive to the presence of life forms and just trundles along as a result of larger forces at play, so life has to adapt to it. Of course this is a fuzzy rather than sharp distinction. Beavers dam rivers and change the environment. Humans may be changing the environment. But the environment itself is not an adaptive replicator.
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Re: Scientists reveal driving force behind evolution

#8  Postby Steviepinhead » Feb 27, 2010 5:20 pm

I want to make a broader, er, point (although narrow points are more in my, hmm, line...).

After just reading up through several threads and news articles, most garnered for us by one Richard Prins, I wanted to welcome him "back" to the larger community that formerly went by the name of the, well, you know, and from which (if I'm understanding correctly) he was an early "refugee"...!

It's great to enjoy once again Richard's web-filtering evo-discovery-locating services! :clap:
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Re: Scientists reveal driving force behind evolution

#9  Postby Spearthrower » Feb 27, 2010 5:21 pm

DanDare wrote:
Spearthrower wrote:
DanDare wrote:That seems to implay an either/or between adaptation to environment vs adaptation to other species. I think its just that environmental changes tend to be slower and less frequent.


I think it's clearer to consider intra- and interspecific conflict as part of the 'environment'.


There is an important difference. Species competing co-evolve. The natural environment, climate, presence of water courses etc. tends to be less reactive to the presence of life forms and just trundles along as a result of larger forces at play, so life has to adapt to it. Of course this is a fuzzy rather than sharp distinction. Beavers dam rivers and change the environment. Humans may be changing the environment. But the environment itself is not an adaptive replicator.


I'm not disputing anything you said, but from the perspective of one individual representing a set of alleles in a population, it's all external. Slowness comparative to the rest of the group that lets it be the one caught by the lion, horns needing to be just big enough to impress the local females but not so big as to vastly outsize the local males, being more adorable than one's siblings, having the ability to process something a little better concurring with a shift in the climate and that resource being more abundant - the selection factors are all external which is, I would say, already covered in the word 'environment'.

What I think you said that was interesting though is that competition creates a more complex environment. More strategies being employed by different agents in the system creates more niche strategies and potential exploitation, but also requires spending resources on running and countering varied strategies too.
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Re: Scientists reveal driving force behind evolution

#10  Postby palindnilap » Feb 27, 2010 8:43 pm

Very interesting stuff. I thought that it was a clear-cut thing that evolutionary arms races leaded to positive feedback, hence faster variation. I am surprised when the article says that the said experiment was the first proven instance. That is an useful reminder that what sounds obvious must not necessarily be true. Is it so hard to test for coevolution ?

Not that it contradicts anything the article says, but surely such behaviours must have already been exhibited in abstract models ?
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Re: Scientists reveal driving force behind evolution

#11  Postby DanDare » Feb 28, 2010 2:35 am

Actually testing coevolution in the lab is somewhat tricky because of the artificial nature of the environment and small population sizes. One species tends to "win", wiping out the other. Computer simulations work better but there is always the need to validate such sims against real events.
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Re: Scientists reveal driving force behind evolution

#12  Postby Someone » Feb 28, 2010 2:49 am

Here is a link to a recent research news article I hope might be found of value here. Not my field, but I stumbled across it and it seems related.

http://www.upenn.edu/pennnews/article.p ... 50&print=1
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Re: Scientists reveal driving force behind evolution

#13  Postby Darwinsbulldog » Feb 28, 2010 4:31 am

Jayjay4547 wrote:
"When an animal carries a “branch” around as a defensive weapon, that branch is under natural selection".
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Re: Scientists reveal driving force behind evolution

#14  Postby DanDare » Feb 28, 2010 3:27 pm

Very interesting article someone.

For those that haven't followed the link two posts up this is how it starts:
PHILADELPHIA –- Researchers at the University of Pennsylvania have developed a theoretical model that informs the understanding of evolution and determines how quickly an organism will evolve using a catalogue of “evolutionary speed limits.” The model provides quantitative predictions for the speed of evolution on various “fitness landscapes,” the dynamic and varied conditions under which bacteria, viruses and even humans adapt.
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Re: Scientists reveal driving force behind evolution

#15  Postby DanDare » Feb 28, 2010 3:29 pm

And the abstract for the Brockhurst paper:
Abstract Microbial microcosm experiments with bacteria and their viral parasites allow us to observe host–parasite coevolution in action. Laboratory populations of microbes evolve rapidly, thanks to their short generation times and huge population sizes. By taking advantage of a “living fossil record” stored in the laboratory freezer, we can directly compare the fitness of hosts and parasites with their actual evolutionary ancestors. Such experiments demonstrate that host–parasite coevolution is an important evolutionary force and a cause of strong and divergent natural selection.
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