Evolution Requires Reduction in Genetic Diversity

Yep, that is on my list for another post on the Silly Design thread. Certainly more like an artist than an engineer ...Enjoy

Thanks, I just do not see how dividing alleles into different populations can result in genetic incompatibility. The alleles are not the genes, but just a part of them. In a population with four alleles: A, B, C and D you can have theses combinations: If we split the population into those with A and B and those with C and D then each subpopulation can have the following combinations: So then if we reintroduce the two populations to each other ... None of those offspring are any different mix than occurred in the parent population, none of those parent varieties did not occur in the parent population.Without any change to the gene how could there be genetic incompatibility?Without any change to any of the alleles, how could there be genetic incompatibility?Even with change to create a new allele, how could there be genetic incompatibility?If we assume a new allele E in population 2 then we get these possible offspring: So the recombined population would then have: There are only two new combinations between pop1 and pop2: AE and BE, so -- unless the of the gene is changed, how could there be genetic incompatibility when the populations recombine?As I see it there is the basic function of the gene, and there are variations that don't affect function but do affect the phenotype (ie alleles).As I see it, to get genetic incompatibility you need to affect the basic function of the gene.Or do I have this wrong?EnjoyEdited by RAZD, : resorted table for clarity

Of course not --- ANY population is inevitably going to develop changes in allele frequency due to genetic drift, it is just more noticeable in small populations.We just know that it is one of many mechanisms that affect evolution of species within habitats. Again, of course we won't --- ANY population is inevitably going to pair recessive alleles through normal mating, it is just more noticeable in small populations. As herebedragons says: founder effect.Any small population without significant selection pressure will see more of the homogenic recessive offspring survive and interbreed than a larger population.We just know that it is one of many mechanisms that affect evolution of species within habitats. That doesn't explain genetic incompatibility. What new combinations? This is the combinations you can have before the split: And that is also the combinations available when reunited -- unless one allele is mutated (D → E in my example).Nor do I see how a new mutated allele can affect genetic compatibility. The possible combinations post mutation are: There are only two new combinations between pop1 and pop2: AE and BE, so -- unless the of the gene is changed, how could there be genetic incompatibility when the populations recombine?What I am trying to do here Faith is draw a line between changes to alleles and changes to gene function. It seems to me that only changes to gene function can cause genetic incompatibility. What I don't see is how shuffling existing alleles changes gene function enough to cause genetic incompatibility.Enjoy

In the latest study they did find some (rare) hybrids between the two northern varieties, so we know that genetic incompatibility is not involved, just shuffling of alleles and some changes to alleles, not to gene function. This of course also means that according to the biological definition of species that trochiloides is in fact all one species. It would seem that this is what is affecting trochiloides as it appears they migrate south to similar locations but spread out in these locations to breed. Is actually just one way that Prezygotic isolation occurs, so I would combine (1) and (2). This would occur via mutations that change the bend sequence\shape of the DNA strand, which would also change the function (protein production) of the gene yes?If that pairing incompatibility were due to a recessive gene, then would not that very same pairing incompatibility prevent that gene to participate in heterozygous mating? The only cases of single mutation speciation that I am aware of involve polyploidy. Indeed. I am reading the first, and note this comment:

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As first noted by MULLER (1942), all hybrid incompatibilities must be asymmetric. Figure 1 shows that, although B might be incompatible with A, a cannot be incompatible with b. The reason is simple: aabb represents an ancestral step in the divergence of these taxa (i.e., aabb is either the genotype of the common ancestor or an intermediate step in the evolution of these taxa). Thus the required fertility/viability of all intermediate steps in the divergence of two taxa places constraints on which incompatibilities are possible and which are not, a point that will recur.

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(figure 1 is on p 1806 and shows the divergence of two theoretical populations with genetic mutations, ie - a → A, b → B, etc)This basically is the potential for genetic incompatibility and requires at least two exclusive mutations, and the first of the untested compatibilities is AB.These untested compatibilities do not occur with all existing alleles in a population.Enjoy

My understanding from reading other articles is that it is the same general area, but not all in one column, and they are grouped by the geological layers they are found in, the names are for groups of layers, just as is done in the Grand Canyon.There are other nearby areas that have also been excavated without finding this lineage (I can provide more if you are interested). btw the thick part of the lines represents two standard deviations within each population ... so 95% of the fossils are grouped in the thick sections at each layer. The thin part of each line represents the full range of fossils from largest to smallest at each interval\layer within the remaining 5%. Here is the transcribed chart again for reference: Yes, because the more fossils found in a layer the better representation you have for the variations within the population. Yes, they are so similar that you can mix fossils from neighboring layers that are in the same size range and then not be able to sort them back out with confidence. Curiously what you have is the data that show just that, albeit with relative age from the layers, not specific dates from any other measurements. What theory Faith? and thus the relative ages of the fossils. Which you know is not true due to the strong degree of overlap in sizes, and because of the time between deposits: why would there be 80% overlap in sizes from one layer to the next if there were some magical sorting mechanism? Why would animals the same size be sorted into different layers? How would animals the same size be sorted into different layers? No Faith, it is looking at -- reading --what the evidence tells us: similar animals in discrete time differentiated layers, layers that have to be from different times laid one on top of the other. You acknowledge that superposition means upper layers came after lower layers Again, why would there be 80% overlap in sizes from one layer to the next if there were some magical sorting mechanism? Why would animals the same size be sorted into different layers? How would animals the same size be sorted into different layers? They were differentiated by age (teeth). Those labels are arbitrary human divisions for the purpose of discussion, based on the layer time intervals. Some other documents break the lineage into more divisions (ie - P. frugivorous just below N.nunienus). It is what the data shows. We know they are related because you could mix the same sizes from adjacent layers and not be able to sort them with confidence, and we know that the upper layer was deposited after the layer below it. Agreed. Mundanely true in that the same animal cannot become two fossils. Which is at odds with the evidence. Thus your interpretation fails to explain the evidence. Also at odds with the evidence that they came from different excavations in the same general area, and that adjacent areas have fossils of similar sized near relative Copelemur fossils but not Pelycodus fossils.So I will agree that Copelemur was a contemporaneous population inhabiting different nearby locations, morphologically similar but distinct enough to separate. Riiiiiiiiiiiiight, the offspring are somehow buried below the parents??? That is what the evidence shows. All we can know is what the data shows, but after several layers of consistent shift to larger sizes and no outliers (the thin lines show the full extent from largest to smallest) we can have confidence that certain size alleles are no longer expressed. Then they would be expressed. Remember that the thick parts of the lines encompass 95% of the fossils found, that the thin lines extend to the largest and smallest fossils in the remaining 5% so the probability of single individuals being significantly outside these limits is very very small. When you consider this small probability recurring at each level the possibility becomes vanishingly small. Precisely as seen at the top of the chart where there is the initial division. Population splits can only select alleles within that population -- selection does not create alleles. That is what you see at the time of the split, but then each population continues to diverge by developing sizes that are NOT in the parent\split population. The large group continues to grow to sizes not seen in previous populations with magical new size alleles, the small group revisits the sizes of the bottom population, but not seen in intermediate populations.If we consider this a test of your hypothesis that alleles are permanently lost then the evidence shows your hypothesis to be false.On the other hand if you now hypothesize that alleles from the parent population not seen expressed in the later populations are hidden but still exist in the "collective genome", then your hypothesis become useless because nothing is truly lost it just gets magically hidden until needed. Irrelevant to your problem. There would be a founder effect, but each population is large enough that inbreeding would not be a problem. Once they have divided selection would drive them further apart to lessen competition.The problem remains that the left hand small group branch recovers alleles that should have been lost if your hypothesis were correct. It isn't necessary, but it does happen. Here we see about a 50/50 split in size but a large variation remaining in each population -- as large a variation as seen in lower populations. In other words you have made up a "get out of jail" card that you can play every time your hypothesis is shown to be falsified by empirical evidence. It is a trend that has not been observed. Ever. What we see is occasional temporary depression of diversity at the time of population division, followed by increase in diversity within each daughter population as new alleles are added. By Mutation. Even when there is a very small founding population with very few alleles.The two populations at the top each have as much diversity as the populations at the bottom. Of course, because you don't accept actual evidence in place of imagination, especially when it invalidates your imagination.Enjoy

No, Faith does understand the law of superposition, but she has a tendency to discard inconvenient facts when the counter her thinking, as you may have noticed.Enjoy

These work for me. Isolation initiates the process and the fixation of genetic incompatibility (post-zygotic separation) completes the process.Isolation may be over many many generations and over widely separate intermediate locations, with populations accumulating mutations, but genetic incompatibility isn't a foregone conclusion, especially if there is no stress/selection to change gene functions. Indeed. With the Asian Greenish Warbler Phylloscopus trochiloides we see separation and variation\modification resulting in a low occurrence of hybrids at the ring end overlap area, due to behavior\song\mating choice, but no definitive evidence of genetic incompatibility ...... however there could be reduced viability if some alleles are lethal but others are viable, and that could be a factor in the low recording of hybrids). From your H. Allen Orr paper The Population Genetics of Speciation: The Evolution of Hybrid Incompatibilities: If the left population had some (a) mixed with some (A) alleles, and the right population had some (b) mixed with some (B) alleles, then you could get: Of these only AB is not tested and could be lethal\sterile, and if so, then reproduction would be depressed compared to normal fertility, with the degree depending on the relative proportions of a:A and b:B in the breeding populations.And of course there could also be interaction with other genes that could affect viability\fertility of the hybrid.And some could be sex-linked so male (A) could mate successfully with female (B) but male (B) would be lethal\sterile when mated with female (A).It comes down to the fixation of the mutated genes in the populations and their effect on viability\fertility when the two populations meet. Exactly. Well I think they are just different forms of isolation, and I would list it

1. genetic incompatibility
2. geological separation
3. ecological separation
4. mating choice separation

... we can agree to disagree, but the way I see it is that there are several ways that subpopulations become isolated, and that it is the isolation that is critical for further genetic divergence.An example of (3) would be your Monkeyflowers, where different pollinators enable the isolation.An example of (4) would be the Asian Greenish Warbler in the overlap zone With the Monkeyflower we see a genetic basis for isolation by causing a shift in how they interact with the ecology (pollinators) while not being genetically incompatible. With the Greenish Warbler we see a genetic basis for isolation by causing a shift in mating preferences (song and wing pattern), while not being genetically incompatible.So the genetic isolation can be initiated with a genetic change without necessarily resulting in genetic incompatibility. [qs]Genetic incompatibility can be very simple as in the case of Mimulus

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Much evidence has shown that postzygotic reproductive isolation (hybrid inviability or sterility) evolves by the accumulation of interlocus incompatibilities between diverging populations. Although in theory only a single pair of incompatible loci is needed to isolate species, empirical work in Drosophila has revealed that hybrid fertility problems often are highly polygenic and complex. In this article we investigate the genetic basis of hybrid sterility between two closely related species of monkeyflower, Mimulus guttatus and M. nasutus. In striking contrast to Drosophila systems, we demonstrate that nearly complete hybrid male sterility in Mimulus results from a simple genetic incompatibility between a single pair of heterospecific loci.

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(For clarity these are different monkeyflowers than the other paper above.)So we have m1f2 sterility but m2f1 (reduced) fertility, interesting. hmmm ... the "V" diagram above is faster growing

# subtitutions	# incompatibilities
1	0
2	1
3	3
4	6
5	10
6	15

or and it doesn't matter which branch the substitutions occur on. And the possibility that one additional substitution enables genetic incompatibility increases dramatically as the number of substitutions increases.What we don't know is how many substitutions are involved in the initial split of the two species populations.For instance if we are at (e) on one branch and have (E) on the other, then even though the other substitutions did not affect viability\fertility the latest one has 4 opportunities to do so.Thanks.

No. The founder effect is the platform on which following populations are build. In order for speciation to occur there must be a genetic difference that inhibits interbreeding when populations reconnect. That difference is shown to be due to different fixed mutations.A small population is more likely to fix more new mutations to be shared as they need every reproductive individual to grow. Here's that "V" diagram discussed above: We can imagine that the left branch is a small founding population and the right branch is the parent population.Even with these mutations becoming fixed in each population, genetic incompatibility is not guaranteed, but without them you don't have any possibility of genetic incompatibiliity, as then all possible combinations are tested. If some combinations of alleles is lethal then it will continue to be lethal. If some combination of alleles is infertile then it will continue to be infertile. Any other combinations get distributed within the population.Enjoy

Curiously I've been on this forum for a little over 10 (yikes) years, and Faith has been here longer ... nothing really changes.What you come to realize (if you don't leave in frustration) is that Faith provides a sounding board that allows us to discuss specific points in detail, whether is is the geology of the Grand Canyon or the genetic basis of evolution.And you come to realize that the point of the debate is not to convince Faith, but to lay out a cogent argument bolstered by empirical evidence so that people lurking can follow -- they are your true audience.Personally I enjoy learning new things from others from their responses.Enjoy

Difficult to know which wiki article you refer to without links, so I am going to assume from other conversations (correct me if I'm wrong) that you mean:Founder effect - Wikipedia

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In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942,[1] using existing theoretical work by those such as Sewall Wright.[2] As a result of the loss of genetic variation, the new population may be distinctively different, both genotypically and phenotypically, from the parent population from which it is derived. In extreme cases, the founder effect is thought to lead to the speciation and subsequent evolution of new species.

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Simple illustration of founder effect. The original population is on the left with three possible founder populations on the right.

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In the figure shown, the original population has nearly equal numbers of blue and red individuals. The three smaller founder populations show that one or the other color may predominate (founder effect), due to random sampling of the original population. A population bottleneck may also cause a founder effect even though it is not strictly a new population.

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... as I know that you will be drawn like a moth to flame by the phrase "the loss of genetic variation" ...The problem is that initially those (all red) or (all blue) populations may appear different, they are not yet different species -- those combinations could and did appear in the parent population, and thus there is no way that they were genetically incompatible with others in the parent population --- yet. For one, Wikipedia is not a source of absolute knowledge, but for two what it says is not exactly what you have been arguing:

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... In extreme cases, the founder effect is thought to lead to the speciation and subsequent evolution of new species

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It doesn't cause speciation, in extreme cases it can lead to speciation. How? What I said in Message 686 was (emphasis added):

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No. The founder effect is the platform on which following populations are build. In order for speciation to occur there must be a genetic difference that inhibits interbreeding when populations reconnect. That difference is shown to be due to different fixed mutations.

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Yes, because the preponderance of evidence shows that mutations occur in every generation, that rarely do offspring have the exact same genetic elements of their parents, because the sun rises every day whether you see it or not. Many do not show up in phenotypes, but are platforms for later mutations that do, and mildly deleterious mutations can still be propagated if the phenotype as a whole is able to survive and breed. You seem to be confusing the appearance of beneficial mutations with the occurrence of all mutations. Most appear to be neutral (intially) or have negligible effect, and thus many are propagated because the whole phenotype is selected.Beneficial\deleterious are also often relative to the ecology (while viable\lethal are related to the individual), and when the ecology changes their relative importance to the survival of the individuals can change -- deleterious can become beneficial, beneficial can become deleterious (pocket mice and lava beds). Let's start with what "fixed" means ... from fixation (wiki)

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In population genetics, fixation is the change in a gene pool from a situation where there exists at least two variants of a particular gene (allele) to a situation where only one of the alleles remains.[1] In the absence of mutation, any allele must eventually be lost completely from the population or fixed (permanently established in the population).[2] Whether a gene will ultimately be lost or fixed is dependent on selection coefficients and chance fluctuations in allelic proportions.[3] ...

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In the process of substitution, a previously non-existent allele arises by mutation and undergoes fixation by spreading through the population by random genetic drift and/or positive selection. Once the frequency of the allele is at 100%, i.e. being the only gene variant present in any member, it is said to be "fixed" in the population.[1]

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So you can't have "fixed RARE alleles" as a fixed allele is the only allele. Because that is how you get something different. Because (a) that is what happens over time, and (b) genetic incompatibility arises between fixed alleles in a breeding population. If you have 'a' (original) and 'A' (derived) alleles in a population and 'b' (original) and 'B' (derived) alleles (at a different loci) then the mating possibilities are: If a mutation arises and is not compatible within the breeding population then it perishes from the population. So of these possible combinations only AB is not necessarily viable while the others necessarily are. If this were within a single breeding population you would have a potential for depressed reproductive\survival results, but not genetic incompatibility, and this would tend to eliminate the new mutations over time.But with population isolation the new mutations that spread in each population are backwardly compatible with the (other loci) alleles of their parent populations. Getting back to the "V" diagram again: When each branch evolves independently with different new alleles becoming fixed within their populations they are each backwardly compatible with the (other loci) alleles of their parent populations, but not necessarily compatible with different new fixed alleles in the other population, as that is not tested within either subpopulation. That opens the door for genetic incompatibility to occur ... that is what makes incompatibility possible.EnjoyEdited by Admin, : Fix dBCodes.

Just a small point Faith, Macroevolution in science means (and always has meant) speciation, and the formation of nested hierarchies.That this is impossible would astound several people who have actually observed speciation and the formation of nested hierarchies. This is sometimes called microevolution, however this is the process through which all species evolve and all evolution occurs at the breeding population level.If we look at the continued effects of evolution over many generations, the accumulation of changes from generation to generation may become sufficient for individuals to develop combinations of traits that are observably different from the ancestral parent population. We saw this pattern with Pelycodus where different species were defined as we went from P.ralstoni to P.jarroviiIf anagenesis was all that occurred, then all life would be one species, readily sharing DNA via horizontal transfer (asexual) and interbreeding (sexual) and various combinations. This is not the case, however, because there is a second process that results in multiple species and increases the diversity of life. The reduction or loss of interbreeding (gene flow, sharing of mutations) between the sub-populations results in different evolutionary responses within the separated sub-populations. Each population then responds independently to their different ecological challenges and opportunities, and this leads to divergence of hereditary traits between the subpopulations, both to adapt to different ecologies and to reduce competition, as seen at the top of the Pelycodus diagram.Scientific macroevolution has occurred, it has been observed, and it is a fact that speciation and the formation of nested hierarchies does occur.Enjoy

Losing the ability to interbreed is the definition of speciation, and this is why people are complaining that you are trying to redefine the terms.Personally I don't see what the problem with new species is for creationist\creationism, as no-one claims that "kinds" are species as far as I know. We have discussed this before, and I have brought up cladistics before. At it's most simplest level, Cladistics is defined as:

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noun, Biology, (used with a plural verb)
1. classification of organisms based on the branchings of descendant lineages from a common ancestor.

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You can start with the "original" common ancestor from the day of creation, or from the "kinds" preserved on the ark, as a creationist, or you can start with species alive today and work your way back to see how far it goes (does it go all the way to "original" breeding populations of archaic bacteria?), as a biologist. The process is the same -- microevolution and speciation. For example:

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... The organisms are placed into charts called cladograms that are divided into clades, groups that share an ancestor.

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An example of a cladogram

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This could be the "bear kind" clade for a creationist, or part of the overall tree of life for a biologist. Whether or not it possesses reduced genetic variability, speciation is defined by the loss of ability to interbreed. Complaining about a word being used in a science the way scientists defined it is sheer pointless madness -- all you will do is cause misunderstanding when you use words to mean different things than the say other people are using them.This is why Percy is asking you to clarify your position.Consider how many times you complain about people not understanding your position, and then consider that it is because of the way you have said things and the words you use. Again, speciation (the loss of ability for two subpopulations to interbreed) has been observed and the formation of a clade at its most simplest level is

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                         ^ speciation
                        / \
                       /   \

This clade includes the parent population and the two genetically incompatible daughter populations. But it doesn't matter whether you call them species, subspecies, subsubspecies or whatever -- it is a fact that this occurs, as it has been observed. They are actual factual daughter populations that have actual factual evolved from a parent species and are actual factual genetically incompatible. Does that meet the scientific definition\usage of speciation? Yes: ergo speciation has occurred, no interpretation needed. Again, why? This says nothing about whether genetic diversity increases, decreases or stays the same. This is the way scienced defines (micro)evolution - which you accept occurs.Whether or not it possesses reduced genetic variability afterwards, evolution is defined by the changes in the composition of hereditary traits, and changes to the frequency of their distributions. Complaining about a word being used in a science the way scientists defined it is sheer pointless madness -- all you will do is cause misunderstanding when you use words to mean different things than the say other people are using them.This is why Percy is asking you to clarify your position. Exactly. Microevolution is the only evolution that occurs. It is how species change over time and it is how speciation occurs when daughter populations lose the ability to interbreed when microevolution in isolation from each other results in genetic incompatibility. And this is where you run into trouble using words to mean something else than the way it is defined in science: the formation of genetically incompatible daughter populations IS macroevolution to scientists, so we know that macroevolution occurs because this has been observed.Can you tell me what you mean by "macroevolution" (presumably something different from the scientific usage\definition)? Yes, Faith -- reading it and disagreeing with it does not mean I haven't read or understood it, just that I don't agree.And when you say things that are contradicted by facts I will continue to point that out.

And then there is the issue of cryptic species -- populations that look alike but can't interbreed. The malaria carrying mosquito is an example: when they were looking for biological control methods they discovered that one kind did not carry the bug and the other did, even though they looked the same. One population bred at dawn and the other at dusk, and a slight variation in the genitalia prevented interbreeding.Species complex - Wikipedia

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... terms sometimes used synonymously but with more precise meanings are: cryptic species for two or more species hidden under one species name, sibling species for two cryptic species that are each others' closest relative, and species flock for a group of closely related species living in the same habitat. ...

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... . It may represent an early stage after speciation, but may also have been separated for a long time period without evolving morphological differences. Hybrid speciation can be a component in the evolution of a species complex.

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Enjoy

Look at it this way Faith: we observe that populations split into subpopulations inhabiting different habitats, they become reproductively isolated ... over time their genetic changes as they adapt to these different habitats produce alleles that cause genetic isolation when they get acquainted. We need a name for this, and the name chosen is "speciation" for convenience. It also matches the biological definition of species as being a breeding population that is reproductively isolated from other breeding populations. The name is arbitrary human identification of a process that exists whether we name it or not.Now you have been trying to say that this happens with subspecies ... a distinction without a purpose that I can see. In cladistics there is not the emphasis on genus and family and all the other taxonomic labels, partly because at the point of separation\genetic isolation you have "species" -- another label for convenience of human communication. All organisms are members of a species breeding population, whether that population has diverged into many daughter, granddaughter, etc, populations.

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                         ^ a
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                       /   \
                      /     \
                     /       ^ b
                  c ^       / \
                   / \     /   \
                  d   e   f     g

Where a, b, and c are speciation events, and we can label their parent populations a, b and c as well. Population a gives rise to populations b and c, population c gives rise to populations d and e and population b gives rise to populations f and g. They are all species as far as cladistics is concerned. The offspring are always members of a species, by definition. From my side of the argument there is never a point at which mutations cannot provide new genetic diversity and replenish the well. If you have speciation -- two populations that become genetically isolated -- you have new species by definition. Not quite, I call the long term changes in the populations and the isolation and development of genetically incompatible daughter populations -- the formation of a clade -- macroevolution. It occurs via evolution within disparate populations. Macroevolution is looking at the larger picture of all species, while microevolution is looking at the changes in a single breeding population.As I see it there are two options for a species -- continued evolution (because nothing is static) ... or extinction. As long as you have mutations and selection mechanisms, evolution will continue to occur. Curiously what you think has little effect on reality. To move beyond the hypothetical concepts you need to show evidence that such decrease in viability occurs.Enjoy

That is in effect what has happened with the dispersal of Homo sapiens out of Africa and spreading in small bands to eventually cover the earth. Polynesians in particular would fit that model. North American natives meeting European explorers are like the closing of a ring species, from different groups spreading around the world.The changes in the different populations appears to be more a result of genetic drift than selection, as it would seem that eye color and shape have little to do with survival or reproduction (other than some element of sexual selection), and skin color seems to be mildly selected by latitude and UV\vitamin D effects (it doesn't prevent people of different skin color from living anywhere).Certainly Europeans and native Americans were reproductively isolated for many generations, evolving unique traits, but also demonstrating that reproductive isolation does not necessarily result in genetic isolation without some selective pressure to change. And even on different islands: each island has a different species of tortoise, adapted to the different ecologies. But there are still opportunities for mutations to provide a survival or reproductive benefit in any one habitat\ecology, and selection would favor those in each habitat\ecology, thus providing new genetic materials for every species, subspecies, variety etc. Not limitless, agreed, but not limited either.Enjoy