RE: Species [arbitrary to a degree]

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> -----Original Message-----
> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> ELurio@aol.com
> >Just to
> >name a few simple problems with the BSC: under the definition as ELurio
> > gives it, lions and tigers are members of the same species (ligers are
> > cross-fertile with tigers, at least), as are grizzlies and polar bears
> > (which produce fertile 'golden bear' offspring, as was discovered by the
> > National Zoo after a romantic liason that the workers were wise not to
try
> > and interrupt...). >>
>
> Actually, grizzlies and polar bears ARE probably the same
> species.

Under the BSC, its problematic.  Under just about every other definition,
including the good old fashioned field zoologist definition, these are
clearly distinct species.  Just goes to show that nature doesn't necessarily
like to play by our book-keeping rules.

As de Queiroz has pointed out, almost everyone agrees what species "are"
(slices out of an evolving lineage), but the disagreement is how we
recognize them.

> Ligers,
> are in fact, "mules,." and are in fact  for the most part
> infertile.

Actually, this is less well tested than people would like to think.  After
all, the discovery of the back-fertility of ligers and tigers came from some
folks who assumed the BSC, put ligers and tigers in the same pen because
they "knew" that ligers were infertile, then wound up with a bunch of
ti-liger (or whatever you would call them) cubs.

In fact, trying to test the degree of back-fertility of ligers and tigons,
although scientifically interesting, should probably not be done because it
runs counter to another important issue: conservation.

As with so many things in zoology, there is a lot of very, very interesting
problems that simply haven't been tested under rigorous scientific
conditions because their isn't the manpower, money, and time for it all.

> Mules,
> in the traditional sense (horse+donkeys), on rare occasions
> produce offspring
> too. But they aren't mules.
>
> Then there's the case of the hybrid elephant, which shows that the genus
> "Loxodanta" shouldn't actually exist.

Actually, I thought the hybrid elephant died prenatally.  If so, it doesn't
really count.

In any case, one can wonder if "Loxodonta" should exist, or if the BSC
should exist.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796