names & numbers

Jim Croft jrc at ANBG.GOV.AU
Tue Oct 16 08:23:08 CDT 2001


> >Incidentally, you need not restrict it to just "published" references.  Any
> >identification of a Museum specimen can serve as an assertion, just as any
> >unpublished pers. comm. from an expert.
>
> I don't think this claim applies to higher classification, however:

I do not see any reason why it can not.  A name is just a name,
regardless of rank, and can serve as a handle for concepts or assertions
no matter where it is...

> most people have databases designed in a strict "parent:child"
> hierarchy. If taxon X belongs to subfamily Y of family Z in one
> classification, and to tribe A of subfamily B of family C in another,
> you have VERY different parent:child links all leading down to the
> same terminal taxon.

This is what alternative taxonomies are about - the rank is not
important... look at fern taxonomy - every second species seems to have
been placed in every second genus over time...

> If anything, this sort of variant supra-generic
> classification is probably *more* common (in terms of numbers of
> species involved) than disagreement about species and genus placement.

Maybe, but I think the extent to which this is the case depends on the
group...  but in the end does it really matter?  We are still talking
about alternative taxonomies and classifications and the mechanisms to
handle them are the same...

> Maybe others here will see a simple workaround to accommodate it, but
> I don't - it's an extremely complex thing to do.

It is possible, but most people seem to think the effort not worth it
and carry around in their head various factoids such as one or three
families of legumes, two or thirty genera of Thelypteridaceae and so on.

> I think it
> necessitates a disassociation of the terminal taxa and the
> alternative hierarchies within the data (in other words, taxa are
> stored *without* being classified, and the phylogenies are stored as
> separate data sets, so you only get the computer to spit out a
> classification for a taxon after you choose which phylogeny you wish
> to view),

More or less, but I do not think disassociation is the right word. More
like multiple associations with many different concepts of taxonomy,
classification, phylogeny or general grouping.

Where it becomes complicated is that most people carry around one or two
of their favourite alternatives in their head, but in reality there are
thousands - one for every time someone utters a concept or assertion.

> OR, you stick with the default, reliance on a single
> classification. Right now, *all* the major on-line databases,
> including ITIS, choose the latter option; a single, invariant higher
> classification. You can't have a child link to two different parents,
> so ITIS will presumably *never* be able to designate alternative
> classifications above the terminal taxa - unless they radically
> change their data structure.

True...  the tradition database solution of a single strict hierachy
with a limited number of predefined ranks is the quickest and easiest to
implement and the easiest to unerstand and interrogate.  To handle
alternative name and taxon structures you have to make up your names,
taxa and classification dynamically and recursively based on the
intersection of a number of tables of information - not a big deal for a
computer with all the bits in all the right places though.

It is a lot more difficult to underatand and implement and you have to
ask yourself is absolute and universal truth worth it.

At the end of the day, most people answer 'no'...

jim




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