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RE: Classification: A Definition



Botterweg, Ronald (R.B.) writes:
 > If, as you state, phylogenetics does away with any absolute ranking
 > and comparison of taxonomic level, and everything indeed becomes
 > only relative [...]

Well -- the position of Phylogenetic Nomenclature is that everything
_always was_ only relative, but now we're admitting it to ourselves.

 > [...], then in the everyday practice this may become very
 > impractical and even almost impossible to tackle large numbers of
 > taxa; for instance, how to deal with: species lists, biodiversity
 > analysis and mappings, standard works of reference (encyclopedias),
 > without a practical classification and listing?

With my PN hat on, I will happily state that Linnaean taxonomy is a
comforting fiction.  HOWEVER, I agree with you that that doesn't in
itself make it a bad thing.  Yes, when you put together an
encyclopaedia, you need an organising principle -- a way of breaking
the studied group down into subgroups -- and Linnaean families are one
way of doing that.  The alternative is the route taken by _The
Dinosauria_, second edition, which has a lot of chapters with
uncomfortable chapters like "Basal Tetanurae" and "Basal Thyreophora",
each covering a paraphyletic group.  But, as ugly as that approach is,
it's probably still more honest.

 > If I understand you well, then, when applied consistently, there
 > should no longer be any reference to families (not even to mention
 > higher ranks), maybe not even genera, and in its most extreme form
 > even the species itself becomes questionable (though I can hardly
 > imagine that anybody would drop that concept).

Ah, well, that's the difference between recognising what's true about
descent (which is what PN is for) and putting labels on things because
it's pragmatically convenient (which is classification).  I wholly
agree that the concept of species will never be discarded EVEN IF it
can be conclusively shown that there is really no such thing as a
species.  Same with genus: it's just so much more convenient to say
"Brachiosaurus" than "FMNH P 25105".

And that is why I cordially disagree with David Marjanovic's claim
that PN makes taxonomy obsolete.  We'll always need alpha taxonomy.

 > For example, besides the two mentioned amphibia websites, large
 > standard works (just a few that I happen to know and use) such as
 > Wilson & Reeder Mammal Species of the World and Walker's Mammals of
 > the World, would become very impractical, loosing overview without
 > classification in orders, families, etc.

A courageous approach would be to do away with chapters completely,
and just order the entries according to a pre-order depth-first
traversal of the hypothesised phylogeny.  But here I am using the word
"courageous" in the Sir Humphrey Appleby sense :-)

 > Is there not a kind of 'reconciliation' possible, for practical
 > reasons, e.g. 'cut-off' ponits/lines in trees, indicating what we
 > call a (particular) family, genus, etc. Yes, this would be
 > classification, but an improved one. Or is this heresy again?

I truly don't know.  It certainly is awfully hard to resist them
tempatation to write things like "... and so representatives of at
least four sauropod families are known from the Wealden".  And
changing that to "at least four clades" only makes things worse.  The
pragmatic truth is that people who work on sauropods know with a
pretty high degree of certainty what is meant by "at least four
sauropod families" ... but peopel who work on, say, angiosperms would
be very badly misled if they interpreted such a statement according to
what "family" means in their world.

 _/|_    ___________________________________________________________________
/o ) \/  Mike Taylor    <mike@indexdata.com>    http://www.miketaylor.org.uk
)_v__/\  There are some good things you can never have too much of.