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Author Topic:   Why Evolution works inside Ecologies
RAZD
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Message 31 of 37 (720631)
02-25-2014 3:27 PM
Reply to: Message 30 by Faith
02-25-2014 2:20 PM


population shift with succession
As usual, all you are doing is ASSERTING that mutations are the cause of genetic changes. The evidence does not prove that mutation caused any of it, such as the blackness of the pocket mice. All that is necessary is that a normally-occurring recessive allele become paired up [abe]: and prolific in the population under selection pressure, and perhaps there are other genetic routes to the same result, but mutation does not have to be one of them. [/abe] It's the same situation as with the peppered moth. All this is is Mendelian type inheritance. Again you are merely ASSUMING mutation.

Mutations or not mutations is NOT the topic.

Working inside ecologies we see a disruptive ecological change -- volcanic lava flow covers previous habitats.

Now we can look at the ecological succession of species as they colonize a disrupted area:

http://en.wikipedia.org/wiki/Ecological_succession

quote:
Ecological succession is the observed process of change in the species structure of an ecological community over time. The community begins with relatively few pioneering plants and animals and develops through increasing complexity until it becomes stable or self-perpetuating as a climax community. The ʺengineʺ of succession, the cause of ecosystem change, is the impact of established species upon their own environments. A consequence of living is the sometimes subtle and sometimes overt alteration of one's own environment.[1]

Successional dynamics beginning with colonization of an area that has not been previously occupied by an ecological community, such as newly exposed rock or sand surfaces, lava flows, newly exposed glacial tills, etc., are referred to as primary succession. The stages of primary succession include pioneer plants (lichens and mosses), grassy stage, smaller shrubs, and trees. Animals begin to return when there is food there for them to eat. When it is a fully functioning ecosystem, it has reached the climax community stage.


In this case we have lava flows creating a new bare rock environment, so the first thing we should see are the pioneering species, including the grasses, then the animals that can feed on the vegetation, such as the mice, and then the predators that feed on the mice.

As each wave colonizes this area they add selection pressure to the existing organisms, so the plants and animals adapt.

Whether there was a mutation or the mice had a melanic allele that (like the Peppered Moths) provided better protection from predators, there certainly was a shift to black mice in these areas that exhibited a lot of black lava rock. The frequencies of the alleles in the mice population shifted from tan to black predominance.

Again, fur color is not a major change, but this was selected because of survival pressure.

The area of the lava flows would have an impact on this type of selection, with small areas not likely to have such sub-population separation and selection - it would need to be big enough that mice moving into the center would be less likely to vacate the area during the day but forage in it at night.

Likewise climate change would be a large area shift in environmental change and so we should tend to see rather permanent adaptations to these changes for species that stay in one place.

Edited by RAZD, : sub

Edited by RAZD, : ..


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This message is a reply to:
 Message 30 by Faith, posted 02-25-2014 2:20 PM Faith has responded

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Faith
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Posts: 25595
From: Nevada, USA
Joined: 10-06-2001
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Message 32 of 37 (720634)
02-25-2014 4:29 PM
Reply to: Message 31 by RAZD
02-25-2014 3:27 PM


Re: population shift with succession
Whether there was a mutation or the mice had a melanic allele that (like the Peppered Moths) provided better protection from predators, there certainly was a shift to black mice in these areas that exhibited a lot of black lava rock. The frequencies of the alleles in the mice population shifted from tan to black predominance.

Again, fur color is not a major change, but this was selected because of survival pressure.

The area of the lava flows would have an impact on this type of selection, with small areas not likely to have such sub-population separation and selection - it would need to be big enough that mice moving into the center would be less likely to vacate the area during the day but forage in it at night.

No problem with any of that. There was certainly selection pressure in the case of the mice.


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 Message 31 by RAZD, posted 02-25-2014 3:27 PM RAZD has acknowledged this reply

    
Taq
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Posts: 6795
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Member Rating: 3.9


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Message 33 of 37 (720638)
02-25-2014 5:19 PM
Reply to: Message 30 by Faith
02-25-2014 2:20 PM


Re: extinction event?
As usual, all you are doing is ASSERTING that mutations are the cause of genetic changes.

We OBSERVE that mutations are the cause of genetic changes.

The evidence does not prove that mutation caused any of it, such as the blackness of the pocket mice. All that is necessary is that a normally-occurring recessive allele become paired up [abe]: and prolific in the population under selection pressure, and perhaps there are other genetic routes to the same result, but mutation does not have to be one of them.

The black allele is a dominant trait. You would know that if you had read the paper that I referenced. Also, the black lava is much younger than the desert that surrounds it. The black allele is strongly selected against in the light colored desert to the point that even the dominant black allele can not be found in populations found any decent distance away from the black lava fields.

This is not the case of a recessive gene becoming prominant. It is dominant, and it doesn't exist in the light colored population, and would not have existed for any appreciable time before the appearance of these black lava islands. The genetic evidence clearly shows that it is the emergence of a mutant allele in the recent past.

Or perhaps you can tell us why the observed mechanisms of mutation could not produce the black allele.


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RAZD
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Posts: 18774
From: the other end of the sidewalk
Joined: 03-14-2004
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Message 34 of 37 (720640)
02-25-2014 6:14 PM
Reply to: Message 33 by Taq
02-25-2014 5:19 PM


topic -- ecological changes
We OBSERVE that mutations are the cause of genetic changes.

What I am much more interested in on this thread is how ecological changes are observed and what we can predict from those observations. As an analogy species are the genes of the ecosystem. As the species change the frequencies of these "alleles" change and the ecology evolves.

For this thread we can say that (micro)evolution is a fact, as we are working in the present, and it has been observed. So we do not need to go into the mechanics and mechanisms of evolution here (feel happy to discuss it elsewhere).

I want to look at the bigger picture.

How does the change in the mice affect the ecology? For this question it doesn't matter how the mice change, just that they do. By being more camouflaged they make it harder for predators (hawks, foxes, etc) and they can spread out into the lava fields. They affect the growth of grasses, while distributing seeds and nutrients, adding to the biomass, providing fertile ground (intentional) for bacteria to work on creating soils that can then support more substantial vegetation (bushes etc).

With drought conditions this succession is limited to desert tolerant species (or species that can become desert tolerant).

But some places will likely experience greater moisture, floods, etc. and the ecological shift will be in a different direction in those areas.

Edited by RAZD, : detail

Edited by RAZD, : ..


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This message is a reply to:
 Message 33 by Taq, posted 02-25-2014 5:19 PM Taq has responded

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 Message 35 by Taq, posted 02-25-2014 6:35 PM RAZD has responded

  
Taq
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Posts: 6795
Joined: 03-06-2009
Member Rating: 3.9


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Message 35 of 37 (720641)
02-25-2014 6:35 PM
Reply to: Message 34 by RAZD
02-25-2014 6:14 PM


Re: topic -- ecological changes
How does the change in the mice affect the ecology?

It could change it drastically. Mice can transport seeds and "fertilizer" where it wasn't present before. This can produce new niches for plants, and other species that depend on them. However, these are probably going to be micro-ecosystems given the relative size of the lava fields.

Like I said before, these are islands of lava. While not quite as drastic, this is like a new volcanic island rising out of the ocean with no other islands around for miles. What you will see is a dynamic interaction between the environment and species as the species evolve to take advantage of the newly opened niches.

With the pocket mouse example we can also see how evolution of ecosystems is affected by geographic distance. There are actually two black lava islands in the study that are separated by hundreds of miles. There is simply no way for the mutations that cause the black allele to spread to the mice next to that other black lava island due to the strong negative selection in the light colored desert. Guess what? There are still black mice on that other black lava field, but they don't have the same mutations as the other black mice. Black fur actually evolved twice through different mechanisms at each of the black islands.


This message is a reply to:
 Message 34 by RAZD, posted 02-25-2014 6:14 PM RAZD has responded

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Faith
Member
Posts: 25595
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.0


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Message 36 of 37 (720655)
02-25-2014 11:56 PM
Reply to: Message 35 by Taq
02-25-2014 6:35 PM


black pocket mice
There is simply no way for the mutations that cause the black allele to spread to the mice next to that other black lava island due to the strong negative selection in the light colored desert. Guess what? There are still black mice on that other black lava field, but they don't have the same mutations as the other black mice. Black fur actually evolved twice through different mechanisms at each of the black islands.

I've moved my part of the pocket mice genetics discussion to the genetics thread, and don't want to continue it here, This is interesting and should be discussed on the other thread.

The odds against mutations occurring for this purpose are just too great, but in any case the better explanation is that the "D for dark" allele was simply most likely extremely rare in the light-colored population and strongly selected for on the lava islands where it therefore began to increase.

From what you say, it sounds like there are different ways a dark coat is genetically produced, through different gene combinations or whatnot, and it would be nice to discuss that on the other thread.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.


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RAZD
Member
Posts: 18774
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 3.8


Message 37 of 37 (720673)
02-26-2014 7:35 AM
Reply to: Message 35 by Taq
02-25-2014 6:35 PM


Re: topic -- ecological changes
With the pocket mouse example we can also see how evolution of ecosystems is affected by geographic distance. There are actually two black lava islands in the study that are separated by hundreds of miles. There is simply no way for the mutations that cause the black allele to spread to the mice next to that other black lava island due to the strong negative selection in the light colored desert. Guess what? There are still black mice on that other black lava field, but they don't have the same mutations as the other black mice. Black fur actually evolved twice through different mechanisms at each of the black islands.

And I agree with Faith that this is interesting but should be discussed on Introduction to Genetics, where she has posted an answer Message 222.

It could change it drastically. Mice can transport seeds and "fertilizer" where it wasn't present before. This can produce new niches for plants, and other species that depend on them. However, these are probably going to be micro-ecosystems given the relative size of the lava fields.

Like I said before, these are islands of lava. While not quite as drastic, this is like a new volcanic island rising out of the ocean with no other islands around for miles. What you will see is a dynamic interaction between the environment and species as the species evolve to take advantage of the newly opened niches.

So we would have some organisms, like the black mice, living on an island in a sea of tan soil, and some organisms, like grass, that aren't directly affected by the rock\soil type.

A mixture of island biogeographic and normal biogeographic distributions.

With climate change, those that are on these islands will need to adapt to the changes, while those not on these islands can move with the climate changes to try to maintian their preferred ecology.


we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)

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