Cladistics and "Eclecticism"

Richard Jensen rjensen at SAINTMARYS.EDU
Mon Feb 4 13:24:23 CST 2002

Thomas DiBenedetto wrote:

Ancestral taxa become higher taxa when some of their descendants become
historically isolated from others of their descendants, i.e when the lineage

> bifurcates. The only thing that comes to an end at the point of bifurcation,
> is the simple fact that the ancestral taxon was a terminal branch in the
> lineage system, and thus ranked as a species. After bifurcation, it's status
> as a species-level taxon is finished. It's life as higher level taxon is
> just beginning. How can this be considered "extinction"?

It's considered extinction because the ancestral taxon which just gave rise to a
single new terminal is no longer a terminal.  As cladists have explained it to
me, if my favorite species undergoes an event in which a peripheral population
is isolated and speciates, then my favorite species no longer exists "as a
species!"  Isn't that what you say above?  If so, I don't accept this line of

I believe that species A, sister to species B, can give rise (as described
above) to species C.  What was a branch with two terminals, is now a branch with
three terminals, two species that continue to exist as before and a third
species that now undergoes its own evolutionary fate, etc.

Richard J. Jensen              TEL: 219-284-4674
Department of Biology      FAX: 219-284-4716
Saint Mary's College         E-mail: rjensen at
Notre Dame, IN  46556

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