Evolution Requires Reduction in Genetic Diversity

Perhaps I misstated something, but I do try to allow for the mutations everybody insists upon even if I doubt their contribution to normal genetic variation; and allowing for mutations means a non-evolving population could gain diversity. Sorry if I said anything that implies otherwise. Upon reintegration? Doesn't sound like anything I'd say. But I do often say that if it becomes part of a population split or other form of selection, then any new diversity will only be subjected to the same reduction in genetic diversity that always occurs with the generation of new phenotypes in microevolution. This is assertion, yes, but it's also logical if you just think it through. Can't have said or meant the "non-diverged" population, since it's the divergence that brings out the new traits along with the loss of genetic diversity. The population of which the novel traits are a part will lose genetic diversity if it evolves, or diverges, which happens with selection or with random population splits, bringing out new traits while reducing genetic diversity. If mutations exist and do anything useful, yes they will contribute added genetic diversity and I can't imagine I ever said anything otherwise. It is WHEN THE PROCESSES OF SELECTION, RANDOM SELECTION AS IN POPULATION SPLITS AT LEAST, are in operation and there IS divergence, that genetic diversity is decreased. You absolutely are not getting it. How much loss of diversity occurs is strictly a function of the size of the population that splits off, or in the case of natural selection how drastic the selection is. If the population is relatively large there may not be an appreciable loss, though there will be SOME loss, but if it's fairly small the loss could be quite great. It doesn't "care" what the level of diversity used to be.

The reduction of diversity only occurs at selection on a phenotype corresponding to the mutation. When a mutation is not subjected to selection pressure it simply makes one animal in the population genetically diverse and possibly phenotypically diverse from its peers. A new eye color gene might be an example of such. By any measure that I care about, this represents an increase in diversity.So if several mutations occur and spread through the population each of which is not subjected to selection is followed by one mutation on which selection operates, the net effect is that the new population is potentially more diverse than the previous population prior to the occurrence of any mutations.I have yet to see you directly tackle the above scenario despite my having given it several times. Just as soon as you decide to make this a part of your model, let me know. The discussion will change to one of you simply denying the evidence we have for mutations that add new alleles. Show me where the definition in Wikipedia excludes the possibility of the generation of new genes and acknowledges only the addition of new alleles for the same gene as constituting genetic diversity. If you cannot do that, then you misread my post.Edited by NoNukes, : No reason given.

Yes, no argument except of course I doubt that mutations ever create anything genetically useful. But hypothetically sure, what you are saying is correct and didn't I just agree that mutations would increase genetic diversity? So why are you arguing about it? Again, true enough. Funny, I thought I'd answered it many times. I've heard of a few, very few, flukes really, but it does not make a difference to my argument as I keep saying, because there must be a decrease in genetic diversity wherever microevolution is actively occurring. It doesn't matter if the mutation is in the evolving pool or in a stable population, but IF new phenotypes are being generated there will be a corresponding loss of genetic diversity IN THAT EVOLVING POOL. I merely pointed out that two of the measures of genetic diversity given in the article are the same as those I've many times referred to as measures of genetic diversity, in answer to HBD who was saying we need to be able to measure it. So your saying "my" definitions are uninteresting, which in that case are the same as Wikipedia's definition, was a strange thing for you to say. I don't know how you got from that to the rest of your comments.

So, why isn't this discussion over? I have provided a scenario under which evolution can occur without a net loss of diversity. Evolution which occurs under this particular scenario need never reach a dead end. Well no. Phenotypes that occur without selection do not reduce diversity. You just end up in a situation with mixed phenotypes which is not a reduction in diversity overall. And as you've already admitted, it is possible to replenish losses in diversity with mutations. Yes, the problem is that a given measure, taken alone, might not cover all possible methods of increasing diversity. If you pick a measure that excludes certain mutations, particularly if those mutations have been observed, then that measure is not a useful definition for this debate even if the measure is useful in some other specific situations. And yet I've shown that it does matter and you've seemingly agreed. The active selection need not remove all diversity added by prior mutations. Only the particular variation on which selection occurs reduces diversity. So when wings are selected, any alleles that affect eye color, tail curling, etc. remain in the gene pool.

You haven't described anything about evolution. You've argued that mutations increase genetic diversity. That's not evolution. Right, if they are mutations they increase genetic diversity. But if you are just talking about scattered new phenotypes within a population that's not evolution, which is the subject here. If, however, those phenotypes come to characterize a new population or be isolated as part of the new characteristics within a new population, that would be evolution, and it would be accompanied by the necessary loss in genetic diversity I'm talking about. And is not evolution which is the formation of new species. Which is not evolution. If and when evolution occurs (leading toward speciation) the increase in diversity will be lost. Not to say any new traits would be lost, should they exist, but genetic diversity in the gene pool would be lost. Both alleles per locus and percentage of heterozygosity would certainly not miss any contributions by mutations. I have? Sorry, hasn't happened. This is just your usual misunderstanding of what I'm arguing. But you think innovative new traits are evolution and they are not. Even if they existed. Evolution is getting a new species which involves enough reproductive isolation to produce a set of traits uniquely characteristic of that species, and it's the processes that bring that about that require loss of genetic diversity. This is true. Wherever even a single trait is selected there will be a corresponding loss of genetic diversity at that locus. This can even serve as a model for what I'm talking about. But the example I keep using is the population split because in that case ALL the new high-frequency traits are in a sense "selected" and alleles for other versions of those traits will be low-frequency and may eventually drop out altogether. It is in whole populations that you get the microevolution that leads to new subspecies.Again, the innovative new traits themselves would not necessarily be lost, they might even dominate the phenotypic presentation of the new species, yet the species itself would be genetically too reduced to continue evolving.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.

Let's try this one again.Yes, the wings mutation would stay in the population along with the alleles for the eye color and type of tail and so on. Scattered in a stable population they could remain there, even get passed on randomly, all without evolution occurring.It's ONLY when evolution occurs that the reduced genetic diversity would occur.And that evolution could occur by the formation of a new separated daughter population.Or it could occur within the original population. That is, the mutated wings, a particular eye color and tail type that are different from that of the population at large, could randomly come to characterize that very population over many generations of breeding exclusively among those individuals that carry those traits. In that case you'd see the same thing occurring as occurs in separated daughter populations reproductively isolated by physical barriers: You'll see the new allleles replace other alleles for the same traits, LOSING THOSE OTHER ALLELES over time, which is the loss of genetic diversity I'm always talking about, until you have a completely new set of traits forming a new subspecies, or even possibly a "species" in the sense of speciation, which also has reduced genetic diversity, even possibly complete genetic depletion, ALTHOUGH it will have new eye color, new tail style AND WINGS. Yet be too genetically depleted to evolve further.

Concerning mutations that create new alleles, you seem to be saying that a new allelic combination involving existing alleles can create "completely new traits and functions," while a new allelic combination involving a newly mutated allele can only create "inconsequential traits." Is that correct?

I'm trying to discourage redefining existing terms. Mutations increasing genetic diversity is most certainly part of the definition of evolution.If what you're trying to say is that in your view mutations do not increase genetic diversity then that is self-evidently false. Using alleles per locus as the measure of genetic diversity, then if a new allele for a locus comes about via mutation it increases the number of alleles at that locus and must of mathematical necessity increase the alleles per locus.

I will try to be clearer but I am using evolution and have always used it to refer to the active acquisition of new phenotypes in a daughter population.I've been VERY clear that if mutations occur they do increase genetic diversity so I don't know how you are get\ing anything else.

No Nukes complained that I thought mutations only made alleles and not genes, talking about alleles as if they were inconsequential small traits. I don't think mutations make either alleles or genes but for the sake of discussion I allowed both and I don't know what happened after that. I'll try to come back to it later.

I don't think you really mean "evolution" in the above passage. For example, you say that the passing on of various alleles in a population would not be evolution, but it most definitely is part of evolution.Might you mean "new phenotype creation?"

But I realized this is only true in the abstract, while in reality single traits can't be selected, it's whole individuals that are selected, for that trait. But you can't select the trait in isolation so you are selecting all the traits possessed by the individuals that possess it, and reducing, even possibly losing, alleles for other traits in the individuals that don't possess the selected trait. That would be a complex math problem but at least you are going to get a new daughter population this way with its own allele frequencies as usual.

This doesn't help resolve the issue I raised, so I'm just going to rule that new allele combinations involving mutated alleles can have just as great an impact on phenotype as those involving existing alleles, and perhaps even greater.

No, I mean active microevolution as I have been using it throughout this discussion. So all I can do is try to see where the confusion lies and try to word things better. But it will have to wait until later.

Just as much I wouldn't argue with, possibly greater no way.