[Re:]Constraints on PERCEPTION AND DIFFICULTIES IN UNDERSTANDING DARWINIAN THERORY...

[Stuart G. Poss]

I suggest you read it and decide if the panbiogeographic problems you are
studying can not be accounted for by predictions expected of Darwin's theory
of evolution by means of natural selection.  Knowing little of the specific
biological systems you are talking about, I would be most interested to learn
just what particular phenomena and biological systems lead you to conclude
they can not be explained by Darwin's central tenant.   The theory would be
violated if one could measure a great array of biological processes at a
variety of scales, deduce their historical origin, and find that the
principal causal mechanism required to explain this variation of organic
biodiversity through time and space is any other than natural selection.  I
know of no evidence that would force me to disagree with Darwin's central
tenant, yet you suggest you have such evidence.  I, for one, would like to
look at it.

I have been studying the biogeography on a world-wide scale among scorpaenoid
fishes, including
those at the Galapagos.   What drives me to do it is perhaps the same
circuitry that inspired Darwin when he collected some of the same specimens,
although I must certainly admit to be being fortunately guided by the genius
of his observations and the refinement of detail numerous others have
subsequently contributed.  In any event, perhaps you can share with us a bit
more specific imformation with respect to the particular molecular and
mechanisms and morphological features involved, as well as to those specific
measures you are referring to in evaluating your data.  I would be especially
interested to learn what it is about pan-biogeography, as you define it, that
forces you to reach the conclusion that Darwin may have been wrong about the
fundamental thesis of his work, namely that evolution occurs by means of
natural selection acting on hereditable diversity that varies in both space
and more importantly with relative recency of common ancestry and rate of
subsequent divergence.

Darwin observed that the Galapagos fauna is unique because of a variety of
effects that occured in time that led to differential selection among
organisms occupying the islands, and that for the most part, these organisms
are most closely related to those he saw on the mainland.  It is unclear what
theory you refer to when you seem to imply that Darwin was incorrect to
interpret the existence of the geographic variation in such features as other
than a consequence of differential selection upon these geographic variants
or that his theory in some way is insufficient to explain a particular fact
of biogeography.  Perhaps you can be more specific as to the precise
morphological and genetic system you are speaking about.

In my own view, Darwin  and his contemporary Hooker, originally identified
the still predominant contemporary issues confronting modern biogeogrphy,
namely how does one explain the origins and relations of different faunas and
floras in a way that best accounts for the history of their biology,
particularly morphology, through time.  Certainly, unknown to either Darwin
or Hooker, there existed early invasions of microbial organisms into the
bodies of other organisms that can confound the principles and techniques of
biogeographic analysis, as the primary explanation of biotic diversity and
origins at some levels of morphological evolution, such as the subcellular.
However, it is unclear what aspect of your theory is necessary, beyond that
posited by Darwin, that would more efficiently predict the organization of
biotic diversity in general.

As noted by Darwin, elements of the natural landscape that serve to
differentiate the viability of organisms, such as their location, will
profoundly influence the course of subsequent selection.  Despite Darwin's
primitive genetic vocabulary, he correctly predicted that charcter
variability is dramatically different between co-occuring traits that are
associated as a result of their heritability, as opposed to those that are
not so associated.  Perhaps, the lack of resolution of his unfortunate
hypothesis of hereditary blending, can be excused since since Morgan and
Watson and Crick weren't active until later to advise him, as they have us.
Nonetheless, he was correct in his fundamental assertions, with regard to the
consequences of explaining known morphological variation.

If the heritability of such traits is in some way strongly associated, as
long known through classical morphology and now through contemporary
molecular genetics, then the observed patterns of covariation in these
features will be more profoundly influenced by causal effects related to the
propinquity of their descent and almost exclusively dependent upon the
historical course of natural selection upon these features rather than by
their geographic location (ignoring the obviously situation that each
individually occupied some space at certain points in time).   It is for this
reason that understanding the precise phylogeny of life is so vitally
important to the study of causal processes in biological systems, including
the correct historical interpretation of their biogeography.

John Grehan wrote:

>  Stuart G. Poss wrote
>
> Gould aptly concludes his article by noting
> >that the correctness of Darwinian theory is at the core of contemporary
> >biological science.
>
> I have not seen the article, so I do not know if Gould specifies what
> constitutes
> Darwinian, theory, but since panbiogeography reaches different conclusions
> about space and time to that of Darwin, and may suggest that Darwin was
> wrong about natural selection as the prime mover of evolution, does this
> mean that panbiogeography is outside "contemporary biological science"?
>
> John Grehan



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_____________________________________________________________________
Stuart G. Poss                       E-mail: Stuart.Poss at usm.edu
Senior Research Scientist & Curator  Tel: (228)872-4238
Gulf Coast Research Laboratory       FAX: (228)872-4204
P.O. Box 7000
Ocean Springs, MS  39566-7000