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Where goes paraphyly, so too polyphyly. (Re: terms)

Mark Siddall mes at zoo.toronto.edu
Wed Jun 22 22:37:38 EST 1994

In an earlier (in fact earliest) post I stated the following:

>monophyletic taxa deserve a formal name.  And by monphyletic, I mean
>those that comprise ALL descendants (to avoid the monophyly holophyly
>paraphyly business).  The ancestor of all protozoa is also an ancestor

It seems that I (and others) have been supremely inept at this avoidance.
Apologies to all uninterested parties.

I do have one final point to make, with the caveat that I am not trying to 
get digs in on David Patterson.  I _am_ enjoying this exchange, though
I admit I might over-state things at times.

Patterson writes:

>my usage is:
>Monophyly - single origin included in group
>Holophyly - monophyly and all descendents
>Paraphyly - monophyly and not all descendents
>Polyphyly - not single origin
>Is this helpful?

I don't think so.  Take the comparison of paraphyly and polyphyly above
and consider the following:

Capital letters indicate taxa included in some higher-level taxon, and
lowercase are excluded.


a   b   c   D   E   F
|   |   |   I   I   I
|___|   |   I   I___I
  |     |   I_____I
  |     |______X     <-- single local/global ancestor and all descendants


A   B   C   d   e   f
I   I   I   |   |   |
I___I   I   |   |___|
  I     I   |_____|
  I     I______|
      X      <-single local/global ancestor but not all descendants


A   B   c   d   E   F
I   I   |   |   I   I
I___I   |   |   I___I
  X     |   |_____X   <- two local ancestors
  |     |______|
      O       <- single global ancestor not all decendants

Thus it would seem that if paraphyly is acceptable to Patterson by the
following definition:

>Paraphyly - monophyly and not all descendents

The so too should polyphyly since there IS a single common ancestor for
any set of taxa regardless of monophyly or paraphyly or polyphyly.
The only distinction is that one (monophyly) includes all descendant
taxa, whereas the the other two do not.

I would contend that if one is going to accept paraphyletic taxa as
being somehow "monophyletic" sensu Ashlock, then so too are polyphyletic
taxa and the term monophyly loses all meaning.


Mark E. Siddall                "I don't mind a parasite...
mes at vims.edu                    I object to a cut-rate one" 
Virginia Inst. Marine Sci.                     - Rick
Gloucester Point, VA, 23062

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