You aren't going to see much of anything with one gene, ...
The example has two genes, each with two alleles.
... it's the mixture of new frequencies of hundreds, thousands of genes, that brings out the new phenotypic picture. ...
Why would this be any different? You still are using genes that exist in the parent gene pool, phenotypes that exist in the breeding population, and as the example in
Message 580 shows you don't get a new phenotype that is not already in the breeding population -- when you ignore selection, mutation and ecological forces, and you are positing a "homogeneous" parent population (and I think you are misusing that word ... what you mean, I believe, is well mixed, all genes/alleles with virtually the same frequencies).
Consider adding a third gene with two alleles to the above example, you would end up with three tables of possible combinations:
Now rather obviously each of these tables would go through the same process generation after generation as in the original example. You don't get a phenotype that is not in the parent population. You don't get a phenotype that cannot breed with the parent population or a similar sub-population.
OR we can add a third allele to one of the genes:
|
| A
| a
| a'
|
| B
| AB
| aB
| a'B
|
| b
| Ab
| ab
| a'b
|
Now, if we consider that an event removes all individuals with the same allele -- say the a' allele -- then you end up with the original example, a breeding population with all phenotypes that exist in the parent population. Yes you have some genetic loss, but you don't have a new phenotype and you don't have a phenotype that cannot breed with the parent population or a similar sub-population -- you just can't get a phenotype that can't breed with the other phenotypes, because you have not created any barrier to breeding within the species/breeding population.
It should also be readily apparent that adding a third gene with two or three alleles will not create anything new, just the mild gene frequency shift seen in the original example or variations on it. We can keep expanding the table, but the results will be similar: no new phenotype that never existed before, no new phenotype that is not capable of breeding with the parent population.
... Although you could get a new population with nothing but, say, changed striping, say in a raccoon population that split off from another population, ...
The genes for variations in striping would exist in the parent population, and you have not shown that it would create a barrier to breeding.
... in large populations with lots of genetic diversity, like the wildebeests, more than one characteristic is going to change: blue hide, smaller stature, different antlers. The alleles for all those charcteristics are in the larger population but they don't get expressed until a new set of gene frequencies allows them to be expressed in the new population.
But you have not shown that they don't or can't get expressed in the original population, (which you posit is "homogeneous"), so there is no reason for them not being expressed -- when you ignore selection, mutation and ecological forces, and you are positing a "homogeneous" parent population (and I still think you mean is well mixed).
Throw in selection and ecological forces and you will see more shift the phenotypes, but you still will not get anything that could not exist in the parent population and breed with the parent population. You can achieve a different
variety (different populations with different coloration, say)
at best, but not a new species.
We do see this happening, but not with a result of a new species without a barrier to reproduction.
Perhaps the best example for you is the
Greenish Warbler, where the original population splits and splits and splits again, with each breeding population being characterized by slightly different coloration and slightly different mating songs -- different varieties. They each have hybrid zones between one population and the next except at the close of the ring, where you have two varieties that do not readily mate (although there are occasional hybrids).
quote:
Genetic data show a pattern very similar to the pattern of variation in plumage and songs. The two northern forms viridanus and plumbeitarsus are highly distinct genetically, but there is a gradient in genetic characteristics through the southern ring of populations. All of these patterns are consistent with the hypothesis, first proposed by Ticehurst (1938), that greenish warblers were once confined to the southern portion of their range and then expanded northward along two pathways, evolving differences as they moved north. When the two expanding fronts met in central Siberia, they were different enough that they do not interbreed.
The different genomes show mutations that added or modified alleles not in the original (or previous) breeding populations.
That is where new phenotypes arise, and that is where breeding isolation develops.
You really should think about this.
Enjoy
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