pierre.deleporte at UNIV-RENNES1.FR
Wed Apr 21 17:33:14 CDT 2004
At 12:35 20/04/2004 -1000, Richard Pyle wrote:
>Pierre Deleporte wrote: > Individuals are rather well circumscribed
>biological systems in
> > themselves.
>R.P. Yes -- certainly more so than populations or taxonomic clusterings. But,
>even individuals are dynamic entities (cycling from a pair of gametes,
>through a succession of material turn-over, through entropy and
>dissolution). Subtly so in mega-fauna; less subtly so in colonial and other
>more "ambiguous" individual organisms.
Agreed. But I suggest to distinguish:
- systems: individuals, colonial organisms (= cohesive biological systems),
populations and social groups (= a number of really interacting
individuals, these interactions constituting the population or group in a
"real system" out there),
- from taxa: whose only "cohesion" is that all the individuals fit our
definition for being member of the same taxon. Taxa don't exist outside our
classification, while interacting groups or populations do.
Thinking of "reality" in terms of concrete systems is of some help.
Fuzziness is one thing, being a real system or a human construct is another.
>R.P. species (or any other taxonomic or other aggregate unit -- including
>subspecies, populations, etc.) are "defined", not "discovered".
Again, a population of interacting individuals may be said to be discovered
(given a clear definition of "interactions"...! see R.P. below). Because if
you don't study the population, the individuals go on interacting. Thus a
population should not be confused with a "subspecies", which includes
non-interacting individuals of the same "subspecies".
Some "aggregate units" you list above are classes, while a cohesive
population is a system which can be "discovered".
>here we have a semantic thorn, because given a definition of "species", one
>could argue that boundaries between those defined units are "discovered", by
>way of acquiring information relevant to the definition.
This is a crucial point. There is possibly a semantic thorn, but not an
There is nothing wrong in "discovering" members of a class according to
one's criteria (and being conscious of applying these criteria). We cannot
class another way. But why not call it classifying (with more or less
problems of fuzziness) rather than "discovering", for sake of clarity? If
"I discover classes" means exactly "I class", there is redundant, and
possibly misleading, vocabulary. I may "discover" that my classification
conventions work well or badly for some specimens, but this is obviously
linked to my criteria.
On the other hand, what I call positivist illusions in classification is to
consider that there exist "self-evident classes" in the world out there
independently of our classification criteria. Biological systems are more
or less self-evident (i.e. materially well-delimited): individual, coherent
social group, population... but classes are not systems, they are human
constructs by definition.
I suggest accordingly that we try to clearly distinguish "population" from
"subspecies" in the discussion. Discovering a cohesive population is not
the same thing as classifying specimens into a subspecies with or without
fuzziness. Not at all. If it were the same, then let's call it a
population, not a "subspecies", and find another name for specimens grouped
together in terminal taxa while they don't belong to the same "real"
populational system of contemporaneous, living, effectively interacting
>To be fair, I believe the implied meaning of "real" in this context is that
>they (taxonomic entities like "species") exist and are identifiable outside
>the scope of "artificial" (=created by humans) definitions of taxonomic units.
>I.e., they are "discovered" in nature; rather than defined.
See positivist classificatory illusions above. I admit that there is little
"scientific discovery" without scientific theory (again contra naive
positivism), while scientific realism means that we believe that there are
real, material systems out there.
But species are not systems, they are classes, they don't "exist" outside
the classificator's brain processes. This doesn't mean that they lack
scientific pertinence. Concepts matter in science.
> > they are "useful or not useful" in a specified context,
>This is a critical point that usually gets forgotten in the various debates
>(e.g., cladistic vs. eclectic applications of Linnaean nomenclature).
Effectively... and the search for the holy grail of a unique-and-optimal
classification may tend to mask the logical point that different purposes
may require different optimal classificatory conventions. Accepting
different classifications for different purposes (including different
species concepts) complicates the picture, but reality is not that simple
and science (and communication) must follow.
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