Paraphyly=mistakes? (There's the rub)

[P.Hovenkamp]

At 02:43 AM 1/14/02 -1000, Richard Pyle wrote:
> > So the previous argument for a "phylocode"-like scheme, which was
> > "The need to accurately communicate phylogenetic hypotheses via
> > nomenclature (which really boils down to the need to communicate using
> > text, rather than requiring graphic images of
> > cladograms)", is now abandoned and a new one is taking its place
>
>Sorry -- Nope, no abandonment.  Just my poor communication skills at work.
>What I meant was, we need the ability to *define* text strings that strictly
>represent phylogenetic nodes.  Cladograms work well, but it can be
>cumbersome to always have to refer to graphic figures when discussing
>hypothesized phylogenies.  By unambiguously defining text strings to
>represent nodes, those text strings can be used in place of graphic
>cladograms when endeavoring to communicate phylogenetic hypotheses.
Sorry - I can't see any difference between this statement and your previous
one - so my objection still appies: you have to look at the cladogram to
see what actually is being communicated. Text strings can not be used "in
place of graphic cladograms".

>Unfortunately, Linnaean names are suboptimally suited to be *defined* as
>nodes, both because of the inherent association with ranks, and also because
>they are ultimately defined by (anchored to) a single point (i.e., the
>Holotype of the type species, etc...)
>
>...which leads to:
>
> > Phylocode names are
> > anchored at two places in the scheme of things, which somehow is supposed
> > to enhance their stability.
>
>It enhances the stability of their definitions, not necessarily implied
>their contents.

There 's the rub again! What use is a definition if the "thing" it points
to is changing all the time? I can see no particular advantage of calling
/Bombacaceae "stable" if you don't know wether it includes /Malvaceae or
not (or is it the other way round?). It is a bit like defining a "thiscar"
(a new word of my own invention) as "the car that is passing my window".
It's a stable definition, but of particularly little use.

> > How that would be is unclear - obviously, such
> > names are likely to be more sensitive to changes in this scheme than names
> > that are connected only at one point to the scheme, picking up changes at
> > two places.
>
>No, not really.  The "Definition" of a Phylocode name remains constant:  it
>is, and always will be, the most recent common ancestor shared by at least
>two different species (or specimens, or nodes, depending on how the name was
>originally defined).  In other words, the "definition" remains constant over
>time (even though the complete scope of its contents may change over time as
>phylogenetic interpretations change).

In fact, it is a perfect "thiscar". You know there must be one, but at each
time you look it's a different creature, with different features.

>When phylogenies are eventually
>solidified, the names (by their definitions) also solidify.
And if classifications solidify, so do the Linnean names they use...

(...)

>I hope that clears up the point I was trying to make, but I fear I've only
>made things more confusing....

I'm afraid so...

P. Hovenkamp
Nationaal Herbarium Nederland - Leiden
PO Box 9514
2300 RA  Leiden
The Netherlands
hovenkamp at nhn.leidenuniv.nl
http://nhncml.leidenuniv.nl/rhb