BSC

[Richard Jensen]

On Thu, 11 Nov 1999, Curtis Clark wrote:

> I think of the BSC as the "Bogus Species Concept"; there is a certain
> elegance to the basic idea, but in practice the failure to realize that the
> ability to interbreed does not correlate with gene flow renders the concept
> untenable even with vertebrates, much less with plants and a whole lot of
> other "ill-behaved" organisms.

The BSC also requires, in addition to ability to interbreed, the
production of fertile offspring which themselves have the ability to
interbreed; in addition, this "gene pool" must retain its identity with
respect to other gene pools.  That doesn't rule out gene flow between
species, but the production of hybrids should not play any significant
role in the evolutionary fate of either species.

I am inclined to disagree with others who argue that the species is the
least arbitrary unit of classification.  For example, in the group I work
with, the oaks, there is not really much uncertaintly about the
recognition of the genus (Quercus) and of several of the major sections
within the genus (section Lobatae, section Quercus).  The real
uncertainty arises when we attempt to recognize species, and this
uncertaintly extends to each species concept.  In oaks, as in most
organisms, the basic species concept that is employed is the classical
morphological species concept (or phenetic species concept).  We don't
have enough information to reliably apply the BSC, and other approaches
have, to date, not provided the resolving power needed to recognize
distinct genetic entities.  Hybridization is quite common among the
morpho-species, but despite this virtually all of them retain a cohesive
set of morphological characters that allows us to recognize a black oak in
Pennsylvania as the same "species" as a black oak in Arkansas.

There are similar problems im many groups of plants.


Richard J. Jensen      |   E-MAIL: rjensen at saintmarys.edu
Dept. of Biology       |   TELEPHONE: 219-284-4674
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