Daniel Smith
Posts: 970
Joined: Sep. 2007
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| Quote (mitschlag @ Feb. 17 2008,05:08) | | Quote (Daniel Smith @ Feb. 16 2008,21:45) | mitschlag,
I'm sure this is not exactly what you're looking for either, but figure 3.37 (on page 134), gives an example of how Schindewolf used suture lines to draw similar conclusions about ammonoids to those he drew from the corals.
Each suture line depicted there represents 1) an ontogenetic developmental stage of two specific ammonoids, ('a' = the Permian adrianitid, and 'b' = the Permian stacheoceratid), AND, 2) a mature phylogenetic stage for various other forms of ammonoids, (with 'a6' and 'b3' being the mature suture lines for the adrianitid and the stacheoceratid respectively). He goes into some detail about this on the surrounding pages, (I also found the same figure repeated later in the book [pg. 209, fig. 3.75] with more explanation there.)
The arrow from 'a3' to 'b1' illustrates the ontogentic stage at which the stacheoceratid splits off from the adrianitid (they share the same first 3 stages -- 'a1-3' ). It's not as obvious to the untrained eye as it is from his coral diagrams, but if you study it closely, you can see that the same principle applies. |
Excellent. Now I get it! :)
I think the issue of suture lines was tainted for me by the statement in Moyne and Neige: | Quote | | Suture line characters are not used in this analysis because of their high variability between the different species of each genus. |
So, I now see the parallel in Schindewolf's claims for corals and ammonoids: an ontogenetic switch.
Is that the gist of his saltationist hypothesis? It looks testable. Are there any molecular-genetic-devolopmental data pertaining thereto in the literature? |
Yes this is the gist of his saltational hypothesis (and one of the cornerstones of his theory). I don't know if anyone has tested it or not. A quick search on Google Scholar turns up many articles that are unavailable, except for the abstracts, without a subscription.
I did find one interesting article (for which the entire article is available) dealing with the subject of chromosomal rearrangements.
Here's the abstract: | Quote | There has been limited corroboration to date for McClintock’s vision
of gene regulation by transposable elements (TEs), although her proposition on the
origin of species by TE-induced complex chromosome reorganizations in combination
with gene mutations, i.e., the involvement of both factors in relatively sudden formations
of species in many plant and animal genera, has been more promising. Moreover,
resolution is in sight for several seemingly contradictory phenomena such as the endless
reshuffling of chromosome structures and gene sequences versus synteny and the
constancy of living fossils (or stasis in general). Recent wide-ranging investigations
have confirmed and enlarged the number of earlier cases of TE target site selection (hot
spots for TE integration), implying preestablished rather than accidental chromosome
rearrangements for nonhomologous recombination of host DNA. The possibility of
a partly predetermined generation of biodiversity and new species is discussed. The
views of several leading transposon experts on the rather abrupt origin of new species
have not been synthesized into the macroevolutionary theory of the punctuated equilibrium
school of paleontology inferred from thoroughly consistent features of the fossil
record. |
As you know, Schindewolf favored Goldschmidt's theory of macromutations via chromosomal rearrangements. Davison has expanded on this as well. I personally don't know enough about it to know if this is the direction you would go in looking for whether or not Schindewolf's saltational mechanism has been tested. What do you think mitschlag?
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"If we all worked on the assumption that what is accepted as true is really true, there would be little hope of advance." Orville Wright
"The presence or absence of a creative super-intelligence is unequivocally a scientific question." Richard Dawkins
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