Question on Predators/ NS

[AFJ]

How much research has been done the role of feral species who may upset the food chain like the asian carp in the Mississippi, or cain toads in Australia? How much factor would this be in natural selection?

[Darby]

It can be a significant change in a local ecosystem, which is what drives selection. "Natural" in this case is just a label - any population affected by the appearance of carp, etc, will either adapt over subsequent generations...or not. It doesn't matter to them where the carp came from, or how it got there.

[AFJ]

I don't mean to be an agitator. I'm just asking myself the question how are a bunch of carp eating everything in sight and multiplying without control going to be a mechanism for variation in the genome?

[canalon]

They are not. No predator is going to create any variations in the genome. The only thing they can do is to select for variations that would make the prey less likely to be eaten by the carp (better avoidance, bad taste,...). Those varaiations would have existed even without the carp, but they have now a strong advantage compared to other variations and will be able to thrive as would never have done without the carp.

Alternatively the carp is going to hunt all prey to death, and the carp population is going to collapse because the ecosystem will not be abl to support it. Then prey are going to multiply again and if there are enough prey the carp population is going to follow repeating the cycle until one of the population is unable to regenerate from the collapse.

Examples of both situations are found.
As for the "natural" selection it was used by Darwint toppose it to the human selection carried out by breeders, but the models are valid even for the non natural invasion of an ecosystem. I do not really see your point. In fact, this would belong more to the ecology forum.

[AFJ]

My point is that Darwin said natural selection was the mechanism for evolution-right? I don't see how that's ever going to happen. The scenario you gave is very good, and natural selection is evident. But you have to have new information in the genome, and NS is taking away from the gene pool through extinction. Am I missing something here?

[AstusAleator]

Darwin said natural selection was the mechanism for evolution-right?

Modern evolutionary theory relies on more than just selection. It must be combined with mechanisms capable of increasing or changing genetic information in order to produce new organisms.

In the case of aggressive invasives - the invader may extirpate native populations before any advantageous mutations or adaptations can occur or become established.

[futurezoologist]

Random mutations give rise to new genetic material, this along with natural selection brings about a variation from the original 'stable' genome.
Example with the carp - an 'original' fish is competing with this introduced carp population for food, the original fish are being out competed and so are dying out, one of these original fish developes a slightly longer nose through a mutation, this gives it an advantage because it is able to reach food between rocks etc that the carp can't so this gene becomes more common etc etc.

You get the point. This is variation from the original genome.