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Re: Geeze, yet another stupid question.



At 02:55 PM 11/22/96 -0500, Jeff Poling wrote:

>   C'mon, Mickey, does anybody *really* wonder what I mean by "dinosaur" and
>"bird" in the context of this question?
>
>[Yes, quite frankly I do.  The term "bird" in particular has no
> taxonomic significance. -- MR ]

   Let's dump the names.  I understand your point, it makes a difference
where you make the break, but the actual groups are irrelevent to my
question and probably confuse the issue.

   You have

F  G H  I J  K
 \/   \/   \/
 C     D   E
  \     \ /
   \     B
    \   /
     \ /
      A

    You break the tree apart, resulting in:

F  G H  I           J  K
 \/   \/             \/
 C     D             E
  \     \
   \     B
    \   /
     \ /
      A

     You've broken E off because you now think E is "something else", it is
no longer an A (in otherwords, you're a Linneanist).  What is E?

     A is paraphyletic.  It is a grouping that is missing a descendant
group, and the term recognizes this.

     If you also break off D and group it with E, the resulting group is
polypheletic.

     The most common answer I got for E alone is monophyletic.  Indeed, it
IS monophyletic.  However, this term doesn't recognize the fact that the
systematist thinks E is now something else, or basically a new group has
sprung up at E.  Mickey suggested that the correct term is "nonsensical,"
and I agree, it's one of the things that confused the hell out of me when I
first started in all this and saw only Linnean taxonomy.  But I would have
thought there was a term for E the same way there is for A, paraphyletic,
and the grouping together of D and E, polypheletic, that recognizes that
something is missing.

[ I'd have just said "monophyletic" also.  If you have a group and all
  of its descendents, then the branching pattern of its sister and
  parent groups doesn't effect it in any way.  In actuality, probably
  *all* monophyletic assemblages (including your "A" above unless you
  intended it to be the progenote) would be like your "E" in terms of
  the "everything else" from which you are distinguishing them.  -- MR ]

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