species concepts Swallowtails)

[Doug Yanega]

>The plain-old biological species concept (BSC) is simply based on genetic
>exchange --- members within a group that can exchange genetic information
>are members of the same species.  Since we know have the ability to
>examine the genome (the complete genetic information) of any organism, we can
>look for signatures of genetic exchange (or lack thereof).   Hence, the
>powerful genetic technologies now avaliable make the BSC the way to go.

Actually, this is the *very* reason molecular systematists favor using the
PSC: if you can find one genetic difference, then this is considered
sufficent evidence to assume an absence of gene flow - the claim is that
the PSC thus subsumes the BSC, and by using molecular techniques, one need
never again mess around with breeding experiments or suffer from a lack
thereof (or be misled by them - the idea being that while one can produce
fertile offspring in crossbreeding experiments, if this does not occur *in
nature*, they must be two species). While this sounds nice and logical, I
still have questions:

        Are the samples the molecular biologists are taking large enough,
and geographically *complete* enough to resolve whether or not all one is
looking at is a cline of genotypes blending across the range of the
species? If, for example, one samples Luna Moths in Georgia and in Ontario
and finds several exclusive, fixed differences, does that mean you've got
two Luna Moth species, or just that it's one species but they need a LOT
more sampling of the intermediate populations? Anyone, I think, would
recognize the latter is a much simpler explanation. But at what scale can
one draw the line? Samples 1000 miles apart? 100 miles? 10 miles? Does
anyone *know* at what spatial scale any given non-migratory species starts
to show genetic differentiation? If it comes down to this, the amount of
work required to get fresh material from the entire geographic range of
every species of organism on earth is a rather daunting prospect, no?
Pretty hard to use this method of species determination "across the board".
Further, what do we do about all those holotypes upon which our entire
taxonomic, nomenclatural edifice rests, if we can't sequence their genomes?
Dump all the old names and start again from scratch?

[Imagine, instead of Papilio glaucus and canadensis, having Papilio
ACTGGGTATACTGAT versus Papilio ACGTGGTCTACTGGT]

>PS  -- neither the PSC or BSC have anything to do with collecting, or
>banning collecting, so the lifetime of this discussion will likely be short.

Okay, let's make a tie-in, then: if you can no longer identify a species
without doing a genetic analysis, then the government will find it even
MORE difficult to control traffic (since they won't be able to ID anything
without having serious hardware at their disposal), so they'll be more
likely to ban ALL collecting, to be on the safe side.

["But, officer, this is _Pieris rapae_! A common exotic pest!" "Oh, yeah?
PROVE it!" - or, alternatively, "Oh yeah? Well, there are 12 genetic
variants in that complex in North America, 3 of which are endemic and
protected now, so how do I know this specimen isn't one of the protected
ones?"]

Just call me Mr. "Worst-Case Scenario".  ;-)
Peace,

Doug Yanega    Depto. de Biologia Geral, Instituto de Ciencias Biologicas,
Univ. Fed. de Minas Gerais, Cx.P. 486, 30.161-970 Belo Horizonte, MG   BRAZIL
phone: 031-448-1223, fax: 031-441-5481  (from U.S., prefix 011-55)
                  http://www.icb.ufmg.br/~dyanega/
  "There are some enterprises in which a careful disorderliness
        is the true method" - Herman Melville, Moby Dick, Chap. 82