What I am trying to say is that separating evolution into microevolution and macroevolution is not only unnecessary, but also that it is confusing to creationists and other people not trained in evolutionary studies because the terms use the same evolutionary forces. I know that the terms microevolution and macroevolution are throw around to try to help educate people, but that does more harm than good. It makes it seem like there are two evolutionary forces acting on the organisms at different levels. The only difference between the terms is the time scale, and when a new species arises it is because of evolution and some isolation effect.
quote:
Within a population of breeding organisms the dynamics within the population will be to breed and mix genetic\hereditary traits. In a steady-state ecology this will give selective advantage to the more average phenotypes within the population, the ones that "stayed" in the middle...
I don't know what you mean by average phenotypes, but I think you mean overdominance (heterozygous advantage/superiority). Under certain environmental conditions a heterozygote will have higher fitness than homozygotes and will cause balancing selection. But to assume the entire genome has overdominance within this environment is too much of a simplification. Each allele (assuming alleles have no affect on each other) and will have an independent reaction to the environment. Other ways alleles react within an environment is dominance, complete dominance, incomplete dominance, and underdominance.
quote:
...we have a sudden change from a single population with a common purpose, to two very similar but slightly different populations in competition for food, habitat, protection from predators, etc.
Be careful in your language. I have never met a population or species with a common purpose (even in human populations). Competition between subpopulations will be dependent on the speciation event. If it was sympatric or parapatric speciation under which prezygotic and postzygotic isolation are causing reproductive isolation, then yes they will compete for resources. If the speciation event was due to allopatric or peripatric speciation then they will not compete for resources because the populations have been spatial isolated.
I think you have a valid hypothesis
quote:
As I see it, this means that the biggest impact on natural selection in both those new populations will be for divergence from each other to lessen the competition, lower negative selection back towards the level that existed before speciation.
But for your argument to hold you need to show that competition between individuals in the single population before the speciation event was lower than competition between individuals in the two populations after sympatric or parapatric speciation.
quote:
As I see it, this means that the biggest impact on natural selection in both those new populations will be for divergence from each other to lessen the competition, lower negative selection back towards the level that existed before speciation. I see this as a period of marked, high selection pressure that can result (and has resulted) in extinction for one or more populations. This added selection pressure to diverge did not exist before speciation and is caused directly by speciation.
If I understand your argument correctly since these two species that divided from a single species are now competing for the same resources there will be strong selection pressure to maximize the efficiency of resource use. I do not see how this is any different from positive selection on an advantageous allele that allows for more efficient resource use.
quote:
The issue is that macroevolution - the divergence of related species - occurs after speciation has already occurred.
In my opinion your argument does not clearly seperate microevolution from macroevolution. The way beneficial mutations arise within a species and the positive selection that acts on the beneficial allele to rise in frequency is the same way beneficial alleles increase in frequency when two species are competing for the same resources. The divergence of two related species can evolutionarily occur the same way as two individuals within the same species. In fact that is how speciation events occur the divergence of individuals within a species.
™ Version 4.2
