need suggestions

[Robin Leech]

Some hybridization does not destroy the species concept between two
species.  Here in Alberta, there are occasional "White-tailed/Mule Deer"
crossings.  The cross occurs between a male white-tail and a female mule
deer, as female mule deer stand still during mating, whereas female
white-tail move forward.  Male mule deer cannot accommocate the "moving
target", whereas male white-tail have no difficulties with a stationary
target.

Within one or two generations, the cross white-tailed/mule deer breed
back to one or the other.  Thus, there is no "hybrid" stock with a
population that is getting bigger.

Thus, there are still White-tailed deer, and still Mule Deer.

Robin Leech

On Fri, 5 Jan 1996, Curtis Clark wrote:

> At 09:47 AM 1/5/96 +0100, Hubert Turner wrote:
> >D.J. Kornet, from Leiden University, has proposed a species concept based
>
> [etc.]
>
> >As a corollary of this species concept it follows that species cannot
> >hybridize, because that would violate the first criterion of permanent
> >splits.
>
> Hybridization does not always invalidate a "permanent split in the
> genealogical network".  As a first example, consider mules.  Since they are
> sterile, no gene transfer between species can occur.  But even if hybrids
> are fertile, that doesn't ensure gene transfer.  Ledyard Stebbins once told
> me after a seminar that my Encelias were a "comparium" (he meant more a
> syngameon, in Verne Grant's sense) just like oaks, and that eventually the
> species would merge back together.  There are two oaks that hybridize in
> California (I can't remember the species offhand) that have fossil records
> back to the late Oligocene, and there are even fossils of apparent hybrids
> from the Miocene, and yet in 30-odd million years they haven't merged back
> together, or even blurred the boundaries much.
>
> Dr. Kornet's theory sounds to me like a mathematical restating of the
> syngameon concept (I'm basing this only on the Taxacom account), which just
> doesn't work, at least not for flowering plants (which are notorious
> hybridizers).  It is genetically immaterial to a species whether it *could*
> interbreed out of existence, unless it *does*.  The theory also does not
> account for lateral gene transfer, by viruses, bioengineers, ot whatever.
> If it were shown that a plant had a gene laterally transfered from an animal
> (or vice-versa), would the whole top of the eukaryote tree become a
> "composite species"?  And yet if lateral transfer is discarded from
> consideration, how would we account for situations where it has cause more
> gene exchange than hybridization?
>
> -------------------------------------------------------------------------
> Curtis Clark        http://www.sci.csupomona.edu/biology/clark/clark.htm
> Biological Sciences Department                     Voice: (909) 869-4062
> California State Polytechnic University, Pomona    FAX:   (909) 869-4396
> Pomona CA 91768-4032                               jcclark at csupomona.edu
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>