Exist sub-species?????

[Richard Jensen]

On Tue, 9 Nov 1999, Doug Yanega wrote:

> Note that I *do* recognize that diagnosability isn't formally sufficient,
> since the PSC also mandates monophyly, but I think we all KNOW that the
> practical limitations are such that rarely (if ever) will those of us
> concerned with nomenclature have sufficient data to delineate the
> phylogenetic relationships of all the populations of a given
> "species-level" taxon, and thus be able to state whether a given taxon is
> or is not truly monophyletic. We therefore may have to choose among evils:
> with about 1 million described taxa, and several million more yet to go,
> would we prefer to describe new taxa such that (a) future generations are
> likely to blithely ignore our work (witness, for example, the Nomina
> Insecta Nearctica, which synonymizes *every* extant subspecific taxon), or
> such that (b) our work - our hypotheses of species rank - will stand until
> and *unless* they're formally challenged, case by case, with hard data? To
> me, this seems likely to come down to just that sort of choice, which may
> reduce at its simplest to whether we'd prefer to err on the side of
> recognizing many *fewer* species than really exist, or *more*. While I'd
> FAR prefer that we didn't have to make such a choice in the first place, I
> think we'll be forced to, sooner or later, and I'd prefer the second type
> of error, myself.
>
> Awaiting the flames,


No flame.  I, too, would prefer that we err by naming too many species.

But I am still bothered by species being based on the minimally
diagnosable units.  It seems to me that in order to determine what these
units are, one must have an a priori method for establishing their
identity in order to collect that data.  How do I know if two populations
are different?  Well, I have to define my populations by some criterion or
criteria, then examine members of each, and demonstrate that both are
diagnosable as "species."  But, this is all contingent on the
criterion/criteria I initially used to determine which population each
individual belonged to.  Of course, what I am describing is a divisive
approach.  I suppose one could use an agglomerative approach and begin by
recording data for every individual and conducting appropriate analyses to
establish the existence of groups that are non-overlapping for at least
one biological character (perhaps differ uniformly for one base pair in
their DNA?).

Of course, the last simply devolves to the absurd - every individual
becomes a species.  To identify evolutionary units, we have to include
aspects of the reproductive behavior and genetic cohesiveness of groups of
individuals.  These are what evolve and it seems that recognition of these
takes us back to the BSC.

Now, I'm awaiting the flames.

Dick

Richard J. Jensen      |   E-MAIL: rjensen at saintmarys.edu
Dept. of Biology       |   TELEPHONE: 219-284-4674
Saint Mary's College   |   FAX: 219-284-4716
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