Farewell to Species - reticulation
jcclark at CSUPOMONA.EDU
Mon Feb 14 22:14:24 CST 2000
At 04:35 PM 00.02.14 -0500, Thomas DiBenedetto wrote:
>But ancestral species are never really "still around" in that sense. If
>lineage has diverged (even if you wish to call it "budded") then you have
>Y shaped lineage (even if you concieve of one of the arms as being much
>thicker or longer than the other). If you wish to place the organisms that
>you encounter in the field, they will be referred to one of the arms of
>"Y" (even if one is not diagnosable with an apomorphy). The stem refers to
>organisms that lived previous to the divergence.
This is an ontological issue. Most people would say that Michael Donogue is
still around even after having diverged, and despite the fact that nearly
every molecule in his body has turned over. Most of us would agree that he,
as an individual, began with his conception and will cease with his death.
It is not necessary for us to have this view; just as Christians can be
"born again", so Michael could be a succession of individuals. But we stick
to the conventional view.
When a Euglena divides, many of us would say that it ceases to exist, and
is replaced by its two "daughter" cells. Again, this is not the only
possible way of looking at it. But many of us see a greater continuity
between the before and after Michaels than between the Euglena and either
of its progeny.
If Michael is still around, it is no less sensible to say that a stem
species is still around. In the case of species that contain long-lived
clones, *some of the same individuals may still be present*; it would be
extremely inconvenient to say that they switched species just because some
peripheral population diverged.
>I always thought that it was our term, and we should fight for it.
Funny how often "our" really means "my". It seems to me that you, too, are
Curtis Clark http://www.csupomona.edu/~jcclark/
Biological Sciences Department Voice: (909) 869-4062
California State Polytechnic University FAX: (909) 869-4078
Pomona CA 91768-4032 USA jcclark at csupomona.edu
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