Oh, but we have. Remember, there are species for whom a "generation" is only a few months or even a few weeks. So you can observe hundreds, even thousands of generations in the space of a few years. Changes such as these are an observed fact.
So what new species have we observed evolving in these occurances? I haven't seen reports of any.
Come on. You were pointed to these 2 or 3 times right back at the beginning of this thread. Are you saying you never read them? Or that you did not understand them?
Nevertheless, here are some again:
Case One: allopatric speciation
Kilias, SN Alahiotis, and M Pelecanos A multifactorial genetic investigation of speciation theory using drosophila melanogaster; Evolution 34:730-737, 1980.
5.3.4 Sexual Isolation as a Byproduct of Adaptation to Environmental Conditions in Drosophila melanogaster Kilias, et al. (1980) exposed [/i]D. melanogaster[/i] populations to different temperature and humidity regimes for several years. They performed mating tests to check for reproductive isolation. They found some sterility in crosses among populations raised under different conditions. (1) They also showed some positive assortative mating. (2) These things were not observed in populations which were separated but raised under the same conditions. (3) They concluded that sexual isolation was produced as a byproduct of selection. (4)
To be more specific, the researchers began with a homgeneous population of D. melanogaster. They divided the population into several different groups. They kept one group as a control group---raising it in the familiar environment it had always been in. (3). They placed each of the others in a new and different environment, including, in some cases, unfamiliar food sources such as bread and meat.
After several years, they found each population well-adapted to its new environment. They also found:
some of the adapted populations could no longer reproduce successfully with other populations --- even though they all came originally from the same parent population (1)
some of the adapted populations refused to mate with other populations. (2)
these observations did not apply to the population kept in its original environment. (3)
Now remember what you said on August 9. post #435
razzelflaben said:gluadys said:Away back in post 158 (july 30) I posted this definition of species. It is basically the biological definition. As far as I am concerned it is the most useful working definition of a species.
Do you have any problems with using it as a standard definition?
If all groups accept the fuzziness, not at all, it seems to work fine for me.
By the biological definition of species (based on reproductive isolation) this experiment produced new species of Drosophila from a common ancestor. Species that refused to breed with other populations descended from the same ancestor and/or were unable to produce fertile offspring when they did mate.
If you check posts by lucaspa elsewhere on this forum (he is a professional biologist) he notes that in some cases the genetic difference between the parent species and the daughter species amounted to 3% of the genome. Humans and chimpanzees are differentiated by only 2%.
Now, is this or is this not a case of direct observation of speciation?
As direct observation, how is it not conclusive evidence that speciation happens? i.e. that evolution happens.
Case 2: Speciation by hybridization
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Speciation.html
Two species of sunflower, the "common sunflower", Helianthus annuus, and the "prairie sunflower", H. petiolaris, grow widely over the western half of the United States. They can interbreed, but only rarely are fertile offspring produced.
However, Rieseberg and colleagues have found evidence that successful hybridization between them has happened naturally in the past. They have shown that three other species of sunflower (each growing in a habitat too harsh for either parental type) are each the product of an ancient hybridization between Helianthus annuus and [/i]H. petiolaris[/i]. Although each of these species has the same diploid number of chromosomes as the parents (2n = 34), they each have a pattern of chromosome segments that have been derived, by genetic recombination, from both the parental genomes. They demonstrated this in several ways, notably by combining RFLP analysis with the polymerase chain reaction (PCR).
They even went on to produce (at a low frequency) annuus x petiolaris hybrids in the greenhouse that mimicked the phenotypes and genotypes of the natural hybrids. (You can read about the results of these monumental studies in the 29 August 2003 issue of Science.)
So here we have both natural speciation (unless you can explain the three other species of sunflower differently) and a laboratory replication of the same speciation.
The laboratory replication is a direct observation of speciation.
Case 3: A unicellular speciation
Bacteria that eat waste nylon-
The ability of a bacterium to consume nylon must be a mutation, as nylon did not even exist until the 1940s. These bacteria metabolize short nylon oligomers with enzymes in their system. These enzymes have come from a frameshift mutation of a gene which codes for an unrelated enzyme. This has been repeated experimentally to test the validity of the theory. In the experiments, non-nylon-metabolizing strains of the bacterium Pseudomonas were grown in media with only nylon oligomers available for food. Within a few generations, the bacteria were producing the enzyme needed to metabolize the oligomers.
For another natural example of the same type of speciation in a Flavobacterium see:
http://www.nmsr.org/nylon.htm
Again, the laboratory experimentation indicates that this speciation has been directly observed.
Now, just what is inconclusive about these observations?
		Upvote
		
		
		0