[tdwg-content] Taxon Concept dilemma

Richard Pyle deepreef at bishopmuseum.org
Mon Jul 5 22:57:02 CEST 2010

Hi Gregor,

While I certainly agree there are many cases where both things happen in the
same publication (i.e., the circumscription for the species "bus" changes,
at the same time "bus" is moved from the genus "Aus" to the genus "Xus"); I
see these as two unrelated things.  

A classic (but rare) example of this would be when two different species,
which are, respectively, the type species of two different genera, are
synonymized as the same species.  In this case, a new species-level concept
is established at the same time that a genus-level name change is forced
(one of the two genera becomes a junior synonym of the other genus).  But
this represents two different things, in my mind.

To change the circumscription of "bus" implies that the set of organisms
included/implied within circumscription has either expanded or contracted.
Doing so may inspire a taxonomist to synonymize genera, or to move a species
circumscription from within one genus circumscription to another genus
circumscription.  But the act of doing either of these things (which
directly affects the circumscriptions of the genera involved), does not have
any impact on the circumscription of the included species.

The point is, the species may change genera as a result of re-defining the
species circumscription; but the mere act of moving a species from one genus
to another does not, by itself, affect the species circumscription (but it
certainly does affect the circumscriptions of the affected genera).  Thus, a
change of the metadata of "GenusName" for a taxonID of a species does not
require a new taxonID. But there are occassions where the change in a
species circumscription (and hence, the need for a new taxonID) will also
(coincidentally) involve a change to the "GenusName" metadata for one or
more of the affected taxonID.


> -----Original Message-----
> From: tdwg-content-bounces at lists.tdwg.org 
> [mailto:tdwg-content-bounces at lists.tdwg.org] On Behalf Of 
> Gregor Hagedorn
> Sent: Monday, July 05, 2010 3:55 AM
> To: David Remsen (GBIF)
> Cc: tdwg-content at lists.tdwg.org Mailing List; Kevin Richards
> Subject: Re: [tdwg-content] Taxon Concept dilemma
> > Higher taxonomy
> >
> > Is it generally agreed that higher taxonomy does not, in itself, 
> > impact the concept (circumscription) and therefore different 
> > classifications of a taxon are not criteria for a concept 
> identifier 
> > change?
> Yes and no, and I think this is the trouble with determining 
> whether the circumscription was changed or not (your point 2 or 3).
> In many cases, transferring a species into a new genus does 
> implicitly change the description, because a set of 
> previously unrecorded or misinterpreted characters has been 
> studied and the genus description is now implicitly correct 
> for these transferred species.
> It may be that the diagnostic characters are still the same, 
> it may be that previous option to misapply a name (previously 
> undetected) now no longer apply.
> For example, conidiogenesis in imperfect fungi is now 
> routinely observed, and transferring a species into a genus 
> with defined conidiogenesis in the last 50 years generally 
> meant that the range of potential identification (correct or 
> misapplied) was drastically changed. This occurs on all 
> higher levels, not only but including genus.
> I have therefore doubts whether the distinction between 2 and 
> 3 should be made a priori; a system where a name change 
> requires a new ID and where the reasoning is based on these 
> IDs could be more flexible to adjust.
> Gregor
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