[Tcs-lc] Concepts of Higher Taxa

[Blum, Stan]

Roger Hyam wrote:

My understanding of the circumscription of a genus is biased towards the
species that are included within it and less so on its description and I
think this is pretty common. As we go up the hierarchy taxa are defined
more by their members than by anything else. An author's definition of a
family is usually more or less just a list of genera arranged into
intermediate taxa of some kind.

I don't believe definition of taxa by membership is commonly held -- at least
not in a strict sense.  The problem of cascading new taxa makes that system
unworkable (IMHO).  If adding a new member to a taxon effectively means
defining a new concept, then any newly identified specimen requires a new set
of all parent taxa all the way to root (life).  That makes every taxonomy
unique -- non-reusable -- and therefore worthless.

Intuitively, a lot of people casually equate content with a definition, but I
it's more like the application of rules against a set of objects (filtering
by circumscription); if you end up with a different set of objects, they must
have been different rules.

Some may want to argue this point, but what I really want to say is that the
strength of TCS is that it's (supposed to be) agnostic about how one defines
taxa (taxonomic concepts).  Therefore, a consistent model applied to all
ranks (or all taxa in a rankless system), from species through kingdom should
work.

-Stan
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mercury.nceas.ucsb.edu/ecoinformatics/pipermail/tcs-lc/attachments/20050329/8a170674/attachment.htm