Keep in mind that a â€œnicheâ€ is a human construct to describe the environment and life/reproductive style of an organism. There are no â€œemptyâ€ niches. There are no empty boxes in an environment sitting around waiting for some organism to evolve â€œintoâ€ them.
Over time populations adapt to an environment and develop a reproductive vector conducive to that environment. Either that or they go extinct. As a human descriptive convenience we say this population â€œinhabits this niche.â€
The â€œnicheâ€ adapted by some trypanosomes requires warm blood of mammals and the Tsetse fly. Without either these organisms do not survive. This was not some â€œemptyâ€ niche waiting for some bug to take advantage. The bugs evolved a reproductive life style that was adequate for their continued survival as a species and we have named this a â€œniche.â€
Often multiple species develop life-style dependencies on the same resources in an environment. Some species of birds and some species of bats depend upon the same populations of insects as food in their environment. If the resource is plentiful then both species (birds and bats) can survive (inhabit the same niche). If competition becomes intense then populations rise and fall with the resource or extinction may occur or adaptations are developed by one (sometimes both) to broaden or change the dependencies. When the latter occurs we say the population has inhabited a new niche. In the case of some bats, developing an ability to feed on mammalian blood in addition to/in place of insects, new niches were exploited. Birds did not evolve in this direction.
When an environment changes and mass extinctions occur the remaining species are better able to express/develop phenotypes that are adequate to new modes of reproductive success. We describe this as â€œradiating into the empty niches.â€ The mass extinctions do not create pre-determined holes with specified requirements into which some sub-species radiate. Instead, a blank sheet of paper is created onto which radiating species write their own survival plans.
Letâ€™s take one of your observations from post #34:
And it seems also that there was in the air enough space and niches for mammalian bats to enter it - yet it is hard to believee that birds could not find these niches or accomodate to them before bats evolved.
You are assuming that having a few species of bird flying around â€œoccupiesâ€ the â€œair nichesâ€ to the exclusion of all other species. And that, since birds were already able to fly they should have â€œoccupiedâ€ all these airborne â€œniches.â€
Birds developed a reproductive life-style that was adequate for their continued survival. Some small little mammal develops useful un-feathered leathery wings and takes to the air to eat insects and develops a reproductive life-style adequate to its survival (even in competition in some areas with birds). So what?
It appears that the evolution of bats had no discernable negative impact on the life-style of birds and the presence of birds appears to not have hampered the evolution of bats.
The bats did not â€œenterâ€ an unused airspace-flying insect-eating unoccupied niche that just happened to be laying around. Bats developed a reproductive scheme that involved flying, eating insects and hiding in caves during the day that did not involve insurmountable competition from any other species and was adequate for their survival. They â€œcreatedâ€ the niche. They exploited the scheme. They survived.
Birds, on the other hand, had no need to develop the same life-style as bats since the scheme(s) they grew into were adequate for their survival.
It all seems like play with magic formula "empty niche". Stasis? - there were no "empty niches". Radiation? - there were lot of "empty niches".
If you are tripping over the vernacular of a human conceived definition then donâ€™t think in those terms.
Stasis: Well adapted to present environment, selective pressures against major phenotype changes, building genetic diversity within the population.
Radiation: Adaptation to changing environment, lower constraints on phenotype changes, expression/usage of prior developed genetic diversity.
That stasis and fast evolution occurs together hand in hand on the same area at the same time concerns nobody.
Well, it concerns you and I donâ€™t think youâ€™re nobody.
The issue is that, from all available evidence, the two do not occur at the same time in the same population.
Note the use of the word "insurmountable" in my post.
Each has developed a scheme to survive.
And each has managed to survive these many millions of years.
But this is off my point.
Birds and bats created different strategies to survive and reproduce which has worked quite well for them. For human convenience we say they occupy niches. In this case, parts of the niches overlap and competition results. Still, from the history of each speciesâ€™ longevity, the schemes each has devised have been adequate to prolong their species for millions of years.
The term â€œnicheâ€ has no effect on the processes involved in evolution. It is a convenient word to use to denote differing survival strategies. Do not let the word constrain your seeing the grander picture.
It's just like mimicry. It doesn't matter if we know genetics behind the phenomenon or not. Genetics explains nothing. If we know that behind developmnet of "eyspots" on butterfly wings is nucleotide chain of C-C-C-G-U-T-A-A...or if it is chain T-T-T-U-C-G-C-G...or it is C-A-T-C-U-G-G-G-... who cares? What we percieve are often perfect patterns, artifical ones. We percieve structure, forms, often beauty. Of course there are pigments, refraction of light etc... There are also genes (A-C-T-U-...) in which information is stored.
â€¦then natural selection through predatory action culls out a lot of the former two leaving a preponderance of the latter. Over millennia the result is an entire species of nice pretty and useful eye-spots.
If we listen music the mechanism how music is coded on CD doesn't explain the beauty of music at all.
Good analogy for the wrong reason. The mechanism of music encoding is all the same. But the specific coding itself is unique to each piece of music. Natural selection, through economic mechanisms, will favor a CD encoded with David Allen Coe singing "You Never Call Me By My Name" over one encoded with Tiny Tim singing "Tip-toe Through the Tulips." It did not take long for the Tiny Tim encoding, like the messy pre-proto eyespot, to be culled from the population. And beauty has nothing to do with either.
It means that color of swans have no survival advantage - they can be white or black as well. Color of their plumage was not selected by "Natural selection" so in this case "Natural selection" is meaningless. It support thesis that "Natural selection" in many cases is no relevant explanation of coloration of species. Consequently "Natural selection" as explanation of evolution is in many cases only darwinistic fancy.
You are really reaching here arenâ€™t you Marty? You are so bent on defeating Natural Selection you have become strung out on the insistence that every facet of Natural Selection is an all-or-nothing item and must be the same for all life kind. Rather stilted, actually.
Natural Selection is reason enough for every attribute in existence for all modes of life. It is by far the best explanation for species attributes we have seen. Your reaching for some metaphysical explanation to account for the observed attributes is sorely lacking in comparison to Natural Selection.
What you miss, I think willingly, is the degree to which selective pressures (say for coloration) differ among species. Bluegenes has already alluded to the other attributes of Swans that make protective coloration less important to their survival. In other species, like Humans, protective coloration was not a major survival factor either. And just because coloration may not be a strong vector of Natural Selection in some species does not mean that Natural Selection is not a strong determiner of other attributes of that species. It is whole that must be viewed.
And your follow-on message indicates that you think Sexual Selection somehow is in conflict with Natural Selection. Again, one or the other, all or nothing thinking.
Your blinders, made of your emotional compunction for the metaphysical without reasoning, are your fancyâ€¦your crutch. Fortunately, your fancies and crutches do not belie the facts of Natural Selection and Evolution.
That Davison, Broom have declared Evolution dead and Goldschmidt, Grasse, et al, lend some support, is just an impassioned attempt to open a place for a metaphysical (not so)IDer. Davisonâ€™s logic is as twisted as Beheâ€™s and the examples in his â€œmanifestoâ€ are as blind as his logic.
What do you mean by "some species"? Give us a number. I have already given it - my estimation is around 99%. 99% species - survival of which has nothing to do with their coloration - they can be black or white (as swans), they can be mimic or not in the same area as is the case of polymorphic species of butterfly of Papilio Dardanus.
All attributes are naturally determined and subject to the rigors of Natural Selection, some more strongly than others. Coloration is a naturally determined attribute of all living things. My estimate is therefore 100% vis-Ã -vis coloration. Body plan is a naturally determined attribute of all living things. My estimate is therefore 100% vis-Ã -vis body plan. Altruism is a naturally determined attribute of all living things. My estimate is therefore 100% vis-Ã -vis altruism. Length, width, height, number of hairs, spines, spikes, shoe size and aesthetic temperament are all naturally determined attributes of all living things. My estimate is therefore 100% vis-Ã -vis length, width, height, number of hairs, spines, spikes, shoe size and aesthetic temperament. Shall I go on?