Paraphyly=mistakes? (There's the rub)

P.Hovenkamp Hovenkamp at NHN.LEIDENUNIV.NL
Mon Jan 14 10:13:03 CST 2002

Richard Pyle wrote in a previous post:
>It's not so clear to me that this represents the "only" useful approach, but
>I fully agree that it represents "a" useful approach -- and an extremely
>important one at that.  So important, in fact, that it deserves much more
>than the contortion of a nomenclatural scheme developed a hindered years
>prior to the notion of evolution.  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 so important, in my opinion, that it deserves its own
>dedicated scheme -- one designed *with* an a-priori understanding of the
>evolutionary process.  One that doesn't hinge so critically on stability
>over time(**).  One that looks an awful lot like the Phylocode.

to which I commented:

> > One thing to note is is that Phylocode is more or less similar to Linnean
> > nomenclature in that it is *not* (in fact, even less) able to communicate
> > phylogenetic hypothese without text. Can anyone tell whether /Bombacaceae
> > is included in /Malvaceae or not without looking at a cladogram?

And now Richard Pyle again:

>I would venture to say that *any* practical nomenclatural system shares this
>weakness; for any system that did, within a text string, explicitly
>communicate every node back to the origin of life -- would almost cetainly
>be wholly impractical!
>The "names" themselves (text strings) are simply a communicative tool -- a
>label to represent a concept.  We're not arguing about the information
>contained within the characters of that text string, we're arguing about
>what concept that (arbitrary) string of characters can be definied to
>represent. It's the implied definitions that concern us here, not the
>information concept of the names as written. One side of the argument
>maintains that those definitions should be strictly limited to
>"holophyletic" definitions, whereas the other side maintains that
>definitions involving paraphyletic groups (i.e., certain subgroups excluded)
>are acceptable in certain circumstances.
>The fundamental difference (in my estimation) between Linnaean-style names
>and Phylocode names, is that the Linanean names are ultimately defined by
>only a single point (the holotype, type-species, etc.); whereas Phylocode
>names are defined by two points (e.g., "the most recent common ancestor of
>both 'A' and 'B'").  Because of the way Phylocode names are defined, those
>definitions are better suited to maintain stability against the dynamic
>"moving target" of hypothesized evolutionary relationships.
>So no, neither Phylocode names nor Linnaean names include within their
>text-strings information to identify evolutionary context (except in the
>case of Linanean multinomials). However, stability of the *definitions* of
>those names is better-maintained in the Phylocode system than in the
>Linnaean system, when trying to have those definitions strictly reflect
>evolutionary affinities.

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
is now abandoned and a new one is taking its place: Phylocode names are
anchored at two places in the scheme of things, which somehow is supposed
to enhance their stability. 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.

P. Hovenkamp
Nationaal Herbarium Nederland - Leiden
PO Box 9514
2300 RA  Leiden
The Netherlands
hovenkamp at

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