"John Wilkins"  wrote in message
news:c7mqjd$262r$1{at}darwin.ediacara.org...
> Perplexed in Peoria  wrote:
>
> > "John Wilkins"  wrote in message
> > news:c7hmdm$i0l$1{at}darwin.ediacara.org...
> > [snip much]
> > > Population structure is not inherited, although allele
> > > frequency is sampled.  [snip]
> >
> > > Species speciate differentially, a kind of sorting process, I grant
you
> > > that, but *selection*? That requires hereditability at the level
> > > concerned (which doesn't happen for species, as new species are formed
> > > from demes, and they inherit demic allele ratios, perhaps, sometimes),
> > > and competition (of a population size large enough to overcome
> > > contingency). Selection is a subset of sorting, and not all sorting
> > > processes are selection processes. For example, you can sort pebbles
by
> > > water action in a riverbed, but it is not selection.
> > >
> > > As Eldredge noted, species do not "moremake" in
the requisite manner
to
> > > be subject to selection. They split, bud and become disrupted, but at
> > > the species level their properties are not inherited. The principle of
> > > parsimony suggests that if we can account for what happens in terms of
a
> > > lower-level process (i.e., a population genetic process) then the
higher
> > > level explanation is otiose.  [snip remainder]
> >
> > I believe that your arguments don't apply to the kind of
species-selection
> > that I describe in my latest response to Guy.  Population structure
> > can be heritable if that structure is an ESS.  Fluctuations from that
> > stable structure are repaired.
>
> Subtle. But is an ESS a species-level property or a population-level
> property? By this I mean, is it a property that must be borne by the
> entire species rather than by parts of it - is it an ESS in a population
> because the boundary conditions of that population form that trade-off
> to be stable, or is it something that must apply to entire species?

First, I should clarify that I am using "ESS" in an extended sense here.  I
am
not restricting the term to behavioral social games, in which the
appropriate
level would be the "society" or set of interacting individuals
rather than a
breeding population.  I am using "ESS" in a more general sense of any
equilibrium of frequency dependent selection.  Therefore, it can apply to
any demic level within which reproduction is mostly closed and mostly
random.

However, note the problem faced by a species within which different
populations adopt different ESSs.  Those individuals that live near the
boundary between the two populations and which paricipate in gene flows
between the two populations will suffer a decrement to their fitness.  So,
it is likely that either the two populations will become two species, or
that one population will "win the election" and impose its choice of ESS
upon the other.

The ESS doesn't *have to* apply to the whole species, but by the definition
of a biological species, it usually will.

> Moreover, a nascent species typically doesn't inherit the mean or mode
> population structure of its parent. Changes in densities of variant
> strategies are one of the things that is supposed to drive speciation.

Yes, but ...  Suppose we have a species which has ESSs stabilized by
frequency dependent selection on 20 different traits.  That is, we have
20 independent ESSs being maintained simultaneously.  Then, due to
a fluctuation, a remote subpopulation deviates from the ESS for one
of those traits.  The fitness losses due to gene flow drive the erection
of reproductive barriers and we have a peripatric speciation.  But the
child species inherits from parent 19 ESS and is "mutant" on one ESS.
Thus, an ESS is a heritable species-level trait.  Quod erat demonstratum.

> > Furthermore, although the maintenance of that population structure
> > takes place using individual-level selection, I don't think that your
> > parsimony argument applies - the species and its gene frequencies
> > cannot be removed from the explanatory structure.
>
> Why not? If a genus, to use a higher taxon term for argument, consisted
> of a number of metaspecies, each of which was arrayed geographically in
> populations similar to their nearest neighbour and with their own
> population structures, would we need to employ the notion of a species
> here? Perhaps "population" is the largest necessary group. So why is
> "species" a causal player here?

I'm not sure I understand your question here.  But I think that your
argument
here presumes that I have yielded to your earlier argument that an ESS is
a population-level entity, rather than a species-level entity.  But, I did
not
yield, so I don't need to answer.  I think.  But if I do need to respond,
please
rephrase the question.
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