On Sat, 17 Jun 1995, Joe Morlan wrote:
> There is still a very serious problem with the PSC which David has failed
> to address. The PSC fails to provide a framework for polytypic species.
> The original morphological species concept gave a separate name for each
> morphologically diagnosable population. The PSC brings us back full
> circle to the 19th century. The great power of the biological species
> concept was to provide a framework for describing intraspecific
> geographical variation. The PSC recognizes the tips of the branches of
> every single subspecies of Downy Woodpecker or Song Sparrow as an
> independent species and provides no nomenclatural basis for pointing out
> that they are really just varieties of a single gene pool with extensive
> hybridization in many areas.

There is no need for "subspecies" with the PSC. Well-
diagnosed subspecies under the BSC would simply be species
under the PSC. Poorly diagnosed subspecies under the BSC
would not be recognized under the PSC.

JM> The last time we discussed this issue on BirdChat, Paul DeBenedictis
wrote: >
> > There are more ominous implications of these viewpoints as
> > well. The 2nd issue of the Proc. of the Nat. Acad. of Sci.
> > (USA) for 1995 has a paper comparing the complete
> > mitochondrial DNA sequences of the great apes with three human
> > populations. The tree below summarizes approximately the
> > diferences (percent of DNA changed) found as a genealogy.
> >
> > |---------------------- chimpanzee
> > --| (from other great apes)
> > | |----------- African human
> > |----------|
> > | |--------- Japanese human
> > |-|
> > |--------- Caucasian human
>
> I pointed out that this result would require recognition of three species
> of humans and asked the proponents of the PSC if this is really the
> direction they want to go.
>
> Thus far, my question remains unanswered.

I doubt that even the most fervid PSCer would split humans
into separate species, especially on the basis of distance (as opposed
to cladistic) data. But since you regard partitioning polytypic
species into subspecies as crucial to a good species concept, Joe,
perhaps you will show how the BSC subspecies criteria are applied to these
human populations.

And speaking of unanswered questions from our
previous discussion, you still have not addressed the charge
that the hybridization criterion of the BSC diagnoses
genealogically incoherent species (oriole and chickadee
examples), and that its potential interbreeding criterion
lumps populations on the flawed basis of overall phenotypic
similarity. Recall that I am not arguing that an extreme version
of the PSC is the best way to diagnose species, but rather
that the BSC is demonstrably flawed and needs either major
overhaul or replacement. The PSC is not the only
alternative to the BSC. You cannot save the BSC by poking holes
in extreme versions of the PSC.

David Wright
dwright at u.washington.edu