Posted on 02/15/2005 7:12:00 AM PST by furball4paws
Laboratory Speciation in Helianthus Evolves a Native Species
DNA examination of five species of Helianthus (H. annuus, H. petiolarus fallax, H. anomalus, H. paradoxus, and H. deserticola) suggested that H. annuus and H. petiolarus fallax are the evolutionary parents of the other three species (Rieseberg 1993, 1995, 1993). All five species are self-incompatible and fertile. Typically, H. annuus (the ancestor of the commercial sunflower) and H. petiolarus fallax form hybrids that are almost fully sterile. However, the few fertile hybrids, when subjected to sib-matings and back crossing regimes yield a new species that is fully fertile and cannot cross with either of the parental species. This new species is virtually identical to H. anomalus. The produced species is genetically isolated from the parents by chromosomal barriers. "Under laboratory conditions these changes are repeatable across independent experiments" (Niklas, p.64). The laboratory derived H. anomalus readily crosses with the native H. anomalus. Results indicate that H. deserticola and H. paradoxus may also have arisen via hybridization of H. annuus and H. petiolarus fallax. These two species have different synthetic capabilities from the parents and live in sandier and drier soils. Hybrid speciation may be common in plants where hybrids often form (see Gilia sp., Grant, 1966, Stebbins, 1959, Arnold, 1995), but is presumed rare in animals where hybrids are less common (however, see the minnow Gila seminuda, Bellini, 1994). Experiments to confirm the evolutionary parents of H. deserticola and H. paradoxus have not been performed. 1. Based on nuclear and chloroplast DNA analysis results, the Theory of Evolution predicts that H. annuus and H. pertiolarus fallax are evolutionary ancestors of H. anomalus, H. deserticola and H. paradoxus. 2. Hybrids of H. annuus and H. petiolarus fallax subjected to different regimes (at least 3) of back crossing and sib-matings, all converged into a new plant species with "nearly identical gene combinations" (Rieseberg) as the native species H. anomalus. This confirms the natural evolutionary parents of H. anomalus as predicted.
References 1. Arnold, J and S.A. Hodges. 1995. Are Natural Hybrids Fit or Unfit Relative to Their Parents? Trends Ecol. Evol. 10:67-71. 2. Bullini, L. 1994. Origin and Evolution of Animals by Hybrid Animal Species. Trends Ecol. Evol. 9:422-6. 3. Futuyma, D.J. 1998. Evolutionary Biology. 3rd. Edition, Sinauer Associates Inc., Sunderland, MA. 4. Grant, V. 1966. The Origin of a New Species of Gilia in a Hybridization Experiment. Genetics 54:1189-99. 5. Niklas, K.J. 1997. The Evolutionary Biology of Plants. Univ. Chicago Press, Chicago, IL. 6. Rieseberg, L.H. 1995. The Role of Hybridization in Evolution: Old Wine in New Skins. Amer. J. Bot. 82:944-53. 7. Rieseberg, L.H., and N.C. Ellstrand. 1993. What Can Molecular and Morphological Markers Tell Us About Plant Hybridization? Crit. Rev. Plant Sci. 12:213-41. 8. Rieseberg, L.H., B. Sinervo, C.R. Linden, M. Ungerer and D.M. Arias. 1996. Role of Gene Interactions in Hybrid Speciation: Evidence from Ancient and Experimental Hybrids. Science 272:741-44.A
Nice, neat, repeatable and meets all scientific criteria for a definitive experiment.
I mean, what's your point? One of the key claims of creationists is that any really new individual type would die out because it couldn't breed. Here we have an example of a fertile hybrid that breeds despite chromosome count differences.
That the article has no point. Or at least not the one the poster claimed. You have a fertile hybrid and discovered - an existing variety that is sexually incompatible with its parents. That may technically be a different "species". But as a dead end in the "tree" as far as is known, it's not even close to "evolution", just another way to use language to fool people.
What do you mean, a dead end in thge tree?
The evolutionary "tree".
Some truth must be suppressed--to make the world safe for lies--even if your name means "only truth."
"You might want to read the article you posted. It was somewhat interesting. [Evoids can read, can't they?]"
Of course I know what it says, I wrote it.
All five Helianthus species mentioned are classic species by definition. H. deserticola, H. anomalus and H. paradoxus are presumed to have arisen by a mechanism of hybridization of H. annuus and H. petiolarus fallax. The laboratory experiments showing the production of H. anomalus by this mechanism strongly support the presumed mechanism for the formation of the native H. anomalus. While all these species form hybrids, they are all not hybrids.
"Where was it published, when, etc? Or am I missing something? "
I compiled this and wrote from the references included in the post. Happy hunting.
If you want to prove evolution, you have to find something that is generally applicable. And preferably something bigger than a bug or a microbe.
It's a loooooong way for example from a hippo to a whale as another thread claimed. How many generations in 50,000,000 years? Divide the difference between the two by that number of generations and see how much water it takes to get that much change in the next generation. And why didn't they keep doing it? You may find 10 or a hundred highly fragmentary fossils that can be made to look more like one or another. But paradoxically, a longer chain creates a bigger problem:
If you can get 100 steps in sequence from one to the other to happen, why doesn't step one happen 100 times over the same period? And step two 99 times. That would scatter intermediates all over the spectrum all over time. Apparently it isn't that easy to happen. And if it isn't that easy, how do you get 100 of them until the mammals we happen to have today are perfectly adapted to earth and water? Is today some special time in history? Why didn't the transitions die out before reproducing? Why are there then so many of them that just happen to turn up? There is a lot of wishful thinking in the bone chips that are so elegantly reconstructed to "show" evolution.
Three other things should be mentioned before this thing goes belly up.
1. Question: how much speciation can be attributed to this type of mechanism? Many plants form hybrids. Could this mechanism be widespread? There are other examples, but I have found none as compelling as this one.
2. If this is even a rare occurrence, imagine how much this mechanism can speed up speciation. A few years work in the laboratory produces a new species. This allows for some explosive speciation on a geologic scale.
3. The fact that the 2 species not yet tested (I'm not sure about this) have different ecological niche preferences should also be considered in the potential for this mechanism to produce rapid speciation.
No one ever said whales descended from hippos. Can you even read?
"Three of five are hybrids or none of five are hybrids. Both statements cannot be true. And the word "presumed" creates more problems for you than it solves because it means you have no evidence but the hypothesis you started with. Or maybe evoids cannot write?"
I have chosen my words quite carefully. I suggest you go back and read the post again and my post where I gave definitions. None of these species are hybrids. Hybrids are sterile. All 5 species are "fully fertile". The 3 derived species went through an intermediary hybrid stage and converged into distinct new species with genetic markers of the 2 parental species.
The word "presumed" causes no problems. A true scientist knows that nothing is proven unambiguously and will always leave room for a possible exception. We are not authoritarians. We study. We consider. We make hypotheses. We test them in laboratory experiments. If the experiments say so, we say the results "confirm" or "support" our hypotheses. As was posted to you earlier, science never proves anything absolutely.
Perhaps you should reread the post as I suggested above. If you do not want to accept that these reasults are "supporting", then where do you think they are lacking?
If you need more light reading on the subject:
http://www.genetics.org/cgi/content/full/167/1/449
egad, js1138 - do you want to give us scientists a blacker eye?
One of our main problems is that no one but us can read our gibberish. You want Mr. Scum, who I am sure is not a scientist to reinforce his view of us as Dr. Mengeles, or do you just want to smack him on the head?
Common ancestor and all. Still, you should be able to get it to adapt to deeper water :-)
I certainly wouldn't want scum to have to learn anything.
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