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Re: Classification: A Definition



On 5/9/07, Colin McHenry <cmchenry@westserv.net.au> wrote:

Hear, hear. The question is, if you're not putting together the phylocode as an alternative classification system, then why are you doing it?

Well, it really boils down to your definition of "classification". Phylogenetic nomenclature might be said not to be a form of classification because it does not deal with classes (in the philosophical sense, not the Linnaean sense) but with entities. It provides methodologies for associating names with real entities (clades). Our understanding of that entity is determined by the scientific process (e.g., cladistic analysis). By contrast, classes are not real entities (although they may correspond to real entities), but groups whose composition is determined by the classifier, rather than by science.

(Maybe someone else with more experience in philosophy can explain it
better--my head's starting to hurt.)

Insistance of the importance recognising major monophyletic groups?
Sure.  Committment to abandoning ranks?  No.

But strict monophyly cannot be used with absolute ranks, at least, not as they are currently used. For example, if we recognize Dinosauria as a class (Linnaean sense) as well as a clade, then the direct ancestor of dinosaurs cannot possibly belong to a monophyletic class. The only solutions would be 1) to allow taxa of the same rank to include each other (which obviates the whole idea of ranks, anyway), or 2) to allow organisms not to belong to any taxon of certain ranks. Neither is permissible under any taxonomic code.

Also, think of Bakker's reclassification of Dinosauria (=Ornithodira,
under his scheme), where Dinosauria is raised to a class and birds can
still only fit by becoming a family!

Of course, if Margulis is right about the eukaryote cytoskeleton being a
result of endosymbiosis with a spirochaete-type bacteria, then the
Eucarya are merely a symbiosis between one branch of the Bacteria and
one branch of the Archea.  I'm still confused about how the Phylocode
will deal with these sorts of tree topologies; if the e.g. Archea
includes all of its descendants, including the Eukarya, and the Eukarya
include the descendants of one branch of the Spirochaetes, then surely
the clade that contains all spirochaetes contains the Eukarya (which are
a subclade of the Archaea) as well.

Clades can overlap. It's right there on the very first page of the rules: http://www.ohiou.edu/phylocode/art1-3.html

Maybe I should just read the
Phylocode - does it cover this issue?

YES, PLEASE! :D

I am constantly astonished by how many people critique the PhyloCode
without having actually read it, especially considering how concise it
is compared to other codes. And it is extremely rare that I see
someone bring up an issue that it does not cover. (There are a few, as
it's still in draft form.)
--
Mike Keesey