new, probably brief subject

[Richard Jensen]

On Mon, 11 Oct 1999, Doug Yanega wrote:

> It was stated clearly in the seminal paper on the PSC that if there is so
> much as ONE character shared by all members of population X that is not
> possessed by any members of population Y, then X and Y are separate
> terminal taxa (species). Obviously, that one defining character can be a
> single base pair. I don't know of any species yet defined on that small a
> foundation, but how the PSC interprets such a case is quite unambiguous,
> since base pairs *are* characters.

So the critical question becomes, "What constitutes a population?"  We
can't use the "ONE character shared by all members of population X that is
not possessed by any members of population Y" because we don't know if
that character is unique to population X until we have defined population
X.  I presume that the populations must be defined with reference to
potential vs. actual gene flow and that if we can document that there is
no gene flow between populations "X" and "Y", and that members of X have
the unique character required, then we may call X a terminal taxon
distinct from Y.  But, isn't this really nothing more than the BSC?

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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