[tdwg-content] Taxon Concept dilemma

[Gregor Hagedorn]

> 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.

I agree in theory. However, in practice, this is hard to distinguish.
A clear case ist that a replacement epithet does NOT change
circumscription. But we already disagree about merging two species: I
don't think is necessarily changes the circumscription, it may only
correct a previous oversight (i.e. that one circumscription is a
subset of the other). But who in practice establishes whether the
larger circumscription is the older or the younger name.

My main concern is however changes of the higher taxon. If a species
was originally placed in a genus circumscribed as leaf spots producing
elliptical spores on a specific host plant, and is moved into a genus
with defined conidiogenesis, we have changed the circumscription, and
previous "identifications" may now be misapplied names.

The central point is that in practice, significant experience and
knowledge about past practices is required, to determine whether a new
taxon ID should be given or not. Computer typists will get it wrong
and experts may disagree about this.

My conclusion is that if every change in genus name is given a new ID,
the system is manageable after assignment of ID. Computers can
synonymize IDs (sameAs), but they cannot retrospectively split them.
:-)

Gregor