Isn't sympatry just a version of reproductive isolation between members of the same species? If so, this isn't a different example and of course genetic diversity decreases as the genes of the parent population are left behind and fewer genes are maximized in the new population. If it is, I will try to get how it's different.
Speciation in sympatry leads to reproductive isolation without any physical barrier to gene flow being involved. It does not necessarily lead to reduction in genetic diversity if the breeding population of the two groups is the same when speciation occurs. Also, once speciation occurs, mutation and evolution do not stop...even after a bottleneck, over time you might find the smaller population has greater diversity than the original larger population.
MIGHT. Sounds awfully conjectural, and I'm trying to get across that I'm talking about an overall trend to reduction, despite the fact that any particular case may show an increase.
In fact, if two species hybridize and the resultant hybrid can no longer breed with either parent species, then speciation has lead to a dramatic increase in genetic diversity in the new species compared to the separate original species.
Hybridization does add alleles so it's not the same kind of process as the others which merely reduce alleles in order to produce new types, and focusing on it can confuse this discussion. My point is that the MAJORITY of the processes that lead to speciation (selection, migration, bottleneck etc) subtract alleles. Perhaps that's a clearer way of putting it. Mutation and hybridization or sexual recombination add them, but the others subtract. The question becomes whether, overall, in the whole evolutionary picture across all species, the factors that increase outstrip the factors that decrease or vice versa.
Whatever isolates the populations, the same mechanisms are at work: each population has a portion of the original gene pool and expresses it phenotypically to the exclusion of the genetic types in the other pool. So, as with Mick's chipmunks, you get two separate varieties of the same species that either have no opportunity, no ability or no interest in interbreeding. And in all these cases genetic diversity IS reduced as in order for the differences in traits to emerge, the alleles for the other forms of those traits must have been eliminated or significantly reduced in the new population or "species."
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Interesting, but you seem to be admitting that speciation can happen.
What you CALL speciation DOES happen ALL THE TIME, but a creationist does not regard it as anything more than variation within a species. LOTS of variations/breeds/subspecies occur all the time, which I've been saying from the beginning, but there is a limit to this process and my whole point here is to suggest that that limit is the fact that the overall trend of the "evolutionary processes" is a reduction in alleles and in genetic diversity which ultimately has an end point, even at its extreme the extinction of the species, and does NOT lead in the direction of genetic increase EXCEPT in particular, less frequent, and temporary cases when hybridization or mutation can be shown to bring this about -- and I'd like to leave these for a separate discussion as they only muddy up the point about the overall genetic reduction that otherwise always accompanies the formation of new "species" (breeds, types, varieties, subspecies).
Yur statement is largely correct except for the expressing of phenotypes that are present in the new population part. The new phenotypes evolve in separation. At the moment when two populations are separated, they are just a subset of the original population. They may have genotype/phenotypes that are present in both populations but the frequencies are different. It is only after time that they will start to adapt and diverge...the absence of gene flow between the two populations will insure that they start becoming phenotypically divergent.
Yes and it is true that I tend to have in mind the dramatic cases where whole rafts of alleles have been completely eliminated from the new population, and the fact that some remain at all, in new frequencies, does mean that diversity itself is not reduced. Still this does it seems to me represent the trend I'm talking about only less dramatically. That is,
getting a new phenotype does always involve the REMOVAL of the alleles for other phenotypes and the more this process of splitting continues the greater the reduction. It does not involve an addition (again, as I understand it, addition of alleles only happens with mutation and hybridization or sexual recombination and I'm trying to treat these as separate processes.)
How is this different than say the processes that separate bears from dogs..elephants from manatees?
If there is IN FACT genetic descent from one to the other the processes ARE the same, but while I could see that elephants and manatees might have that relationship (without knowing the genetics involved of course), I can't see it between bears and dogs. Bears and raccoons, yes. Dogs and wolves yes. (Perhaps hyenas are not related as some have suggested earlier in the thread, but subjectively I would want to include them with dogs). Admittedly this is a subjective categorization but while there may be no evidence for it, there is no evidence against it either. Evolution assumes genetic descent partly because there has not been shown any stopping point in the evolutionary processes under discussion but creationists deny it and there is no evidence for it. All you have is the observed mechanisms of species variation we are discussing, and again, the overall trend in the edevelopment of such new types or variations or breeds is to genetic reduction (again, for the purpose of highlighting this fact leaving out mutation and hybridization)which hardly supports evolution. And again, the very possibility of evolution apparently depends completely on mutation and the other additive processes as the majority of what have been called evolutionary processes only subtract genetic potentials. And again again, I'm trying to keep the focus on these subtracting processes in this thread.
Or were possibly recessive until the dominant forms were eliminated and allowed them to come to expression in the phenotype. Or were produced by genetic drift or whatever, again all processes that involve the reduction of genetic diversity in the service of developing new phenotypes, traits, characteristics, "species."
This again makes no sense. If there are 8 blue balls and 2 red ball in a population and one red ball goes on to found a new population, the red phenotype is not surpressed in the old population.
I don't see how the term "suppression" came into this at this point, but I think maybe the general point got discussed above.
It is at a lower frequency. After a few hundred generations, maybe there are no red balls left in the original population by chance or selection..but the red ball population has grown and has new mutants, say purple.
Please do not introduce the idea of mutation in this discussion. For the sake of clarity I need to keep the discussion confined to the genetic situation given at the time of the split of the populations. If one red ball creates a new population it will be a population of red balls. Since one red ball stays behind in the old population it will now occur at this new reduced frequency. But it WILL be a REDUCED frequency of red balls as one of the two has left. Therefore the blue balls will dominate even MORE in the old population than they did before the split. It will be a BLUER parent population. And this will have occurred because of the REMOVAL of a red ball. The point is always that the removal or elimination of some genetic potential is the WAY new types emerge through these particular processes [selection, (natural, domestic or sexual), migration, bottleneck etc.] what you call "speciation." And again, this is to leave out mutation and hybridization for the moment, simply in order to demonstrate that the process I'm focusing on is a process of removal or reduction, and leaving out hybridization and mutation it is ALWAYS a process of removal or reduction.
Now you have two populations, one all blue, and one with red and purple...this is what we observe. Not that if you are suddenly isolated you just grow a new phenotype. What you are proposing is basically Lamarkism which was refuted long ago.
See above. I don't know how you are reading me to be saying we're "growing a new phenotype." And again, please leave out mutation in order that these processes I'm trying to highlight can be seen clearly as the reducing processes they are. Which gives us a BLUER parent population (purple but less red-purple and more blue-purple than before) and an all-red new population.
You are giving new examples but there's no difference in the genetic picture that I can see --
This is the point...there is no difference between generation of a new population, species, genus, family, order etc. the process is the same. The only difference is the length of time involved.
This is simply evolutionist faith, an assumption that is taken for granted but has not been proved. But if there is an overall reduction in genetic potential or diversity with these processes (selection, migration, population reduction and reduction of breeding etc) that lead to "speciation," then there is a natural end point to evolution and that end point is the limits of variation/subspecies formation possible in all directions within the Kind beyond which only extinction is possible.
Two closely related species may be equally genetically diverse because since they speciated, they have built up genetic diversity after the reduction. This is directly observable. This is what we see.
Are you talking about hybridization or what? What exactly is it you are "seeing?" This does get into the other subject I've been trying to keep separate, mutation and other additive processes like hybridization, and crashfrog also claimed that even the cheetah shows a buildup of such diversity. I'm afraid of confusing the topic by getting into this, but I really do not know what it is you think you are actually SEEING. The cheetah is about as genetically compromised as you can get, so if it has been accumulating diversity it isn't the greatest case for evolution anyway.
Evolution is change over time..the more time, the more change..it is exactly what we see looking at genetics and and to some extent, morphology, no matter what taxanomic level we are considering.
Creationists answer that all the changes that are seen are limited by the Kind, and I'm trying to suggest a major mechanism how that may happen. Evolutionists always answer that they can't prove their belief that it is open-ended because of the time factor, but all the observations that have been made suggest nothing more than that variation is possible and in fact may be highly frequent, within a species or Kind without implying anything beyond the species or Kind.
I'm not sure what this focus on lineages is intended to prove, but as with the above, I expect variation within species and nothing about it contradicts creationist expectations so if you think it does I hope you will be more specific.
It contradicts creationist expectations because in all cases it contradicts the concept of immutable kinds.
Not at all. All that has happened is that evolutions have been ASSUMING an openended process, but they can't demonstrate it.
The fact that every individual is born with novel mutations contradicts "genetic allotment".
Now we are getting into mutations and I want to think about that separately.
Everything from the biochemistry of DNA, RNA and proteins to the study of mutations segregating in families, groups, populations, species, genera, etc. demonstrates that evolution occurs. Where it cannot be directly measured (over millions of years) it leaves behind footprints exactly like those we observe today. Even ancient DNA lets us directly observe the process over vast time spans.
I see, so I guess I don't have to bother thinking about the selection processes that show this to be highly unlikely. In any case, this is just a statement of faith, an abstraction that needs serious unpacking if I'm going to understand any of it.
What creationists fail to do is show how the different levels of divergence in mick's example, or any example are different biologically i.e. what is the difference between dogs and cats diverging as opposed to house cats from cheetah's?
Evolutionists have never shown that there is any genetic connection between dogs and cats. You simply assume it. No problem with cats though. All cats are of one Kind. A cheetah is a cat related to the house cat. They both diverged from earlier cats, which diverged from the original Cat.
Every piece of evidence ever gathered says there is no difference in the underlying process.
But every piece of evidence only demonstrates what everybody knows about breeding, and nothing whatever that shows you can get anything but a dog from a dog.
Creationism is the denial of this evidence.
Not at all, it is a different understanding of the evidence.
Creationism denies that mutations increase diversity even within a species.
I haven't yet seen this convincingly demonstrated at all. What diversity there is appears to be useless evolutionarily anyway, and when the reducing processes like selection get to work on it in order to speciate it you are reducing genetic diversity anyway as I've been saying, so you still have to show that the increasing factors outdo the decreasing factors.
But other than arguments about contradicting faith or personal beliefs and asthetics, creationism does this with no supporting evidence and loads of evidence that contradicts it.
There is very little evidence that can't be explained in creationist terms without any reference whatever to faith or belief etc.
This message has been edited by Faith, 12-01-2005 11:46 AM
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