Tim Tyler  wrote:

> John Wilkins  wrote or quoted:
> > Tim Tyler  wrote:
> 
> > Sorting can occur on aggregates as much as on particles. Selection can
> > only occur on reproducing particles, and so if species are subjected to
> > selection, they must behave as particles in that process. It is my
> > opinion species do not ever behave as particles in a process unless the
> > species is co-extensive with a single localised population.
> 
> In what manner are you claiming that species must behave as particles to
> be the subject of selection?

The logic of selection is that there is some logical atom that
correlates environmental constants with probability of reproduction.
Chemical selection has isomers which will replicate under fixed
conditions. Organismic selection correlates ecological traits with
probability of reproduction (and hence of the traits). Species selection
would require some aspect of the species itself, a property not merely
the aggregate of the properties of its parts, and an environment that
persists over the duration of many species.

It is my view that this is logically possible, and practically
unrealised. What I think Gould is really discussing, and Vrba before
him, is the sorting of species according to the aggregate properties of
their members.

This may sound like a semantic quibble, and Larry has in the past stated
that he thinks it is. I think it is a matter of giving terms a solid
meaning and sticking with it. Which is.. err... a semantic quibble, I
guess.

[A similar concern is raised in the context of the
species-as-individuals debate -proponents and critics alike seem to
think that there is one sense of "individual" and that it must include
cohesion. A cohesive individual could in principle be subject to
selection, but there are other senses of "individual" and the most
relevant one is "not-a-universal".]
> 
> If species easily merged together then there might be little significance
> to species-level selection - but it is widely accepted that they don't
> deviate from particulate behaviour in *that* particular respect.

Umm, that all depends on the nature of the organisms - gamete
broadcasters like plants, corals, some fishes, *do* speciate in that
manner. Ferns (Pteridophytes) have something like a 97% allopolyploid
speciation.

Hey, if you are right, then we should see no speciation trends in
Pteridophytes...
> 
> What else might be needed?
> 
> From your statements, it seems you are claiming geographic localisiation
> is important for selection between species to take place.
> 
> If so, why might that be?
> 
> What prevents "choosing" the red species and obliterating
the blue species
> if their individuals happen to be distributed and/or intermingled?

I'm not sure why you get that impression, as I don't think selection
happens between species much, if at all, and I do think a lot (not the
majority) of speciation is sympatric. But I have only an amateur's
appreciation of these things.
> 
> IMO, species' gene pools form "particulate" blobs in gene space.
> 
> They may be a /little/ bit smeared out in that space, but are quite 
> particulate enough to permit selection between them to take place.

Can selection take place between anything that occupies a metric space
in virtue of that fact, or do they need to have some cohesion? I think
they do. Clouds have locations, but they aren't selected between.
-- 
John Wilkins
john_SPAM{at}wilkins.id.au   http://www.wilkins.id.au
"Men mark it when they hit, but do not mark it when they miss" 
                                               - Francis Bacon
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