mother-daughter species

[Ken Kinman]

    I have to agree with Richard (Jensen).  Raising Homo sapiens to a higher
taxon in the "Mars" example makes no sense, and to me this is an example of
the "semantics" I referred to when I started this thread on "cladism's
greatest weakness".
     As much as cladists may dislike the concept, I think it would be
helpful to stop trying to shoehorn every cladogenetic event into the mold of
two sister groups emerging.  If cladists have really abandoned Hennig's
assumption of ancestral species extinction, then I see little reason that
they should object to recognizing mother species and daughter species, and
of mother (paraphyletc) groups giving rise to daughter groups.
     As Richard Zander noted in his last posting (which I thought was very
insightful), our emphasis should be on useful tools (conceptual or
otherwise) and practical methodologies (at least I hope my paraphrasing
reflects his meaning).  As I learned from my systematics professor, Peter
Ashlock, cladistics should be treated as a very useful tool.  This is very
different from strict cladism, in which cladistic classifications become
almost a way of life (virtually ignoring any importance for anagenetic
"divergence").
     So I would only reiterate that final sentence in my 1994 book, my hope
that it would "promote the positive attributes of cladistics at the same
time it attempts to eliminate the undesirable side effects of the unbridled
use of this valuable tool in classifications (and being a tool, cladistics
should serve us, not tie our hands)."  I only wish Peter Ashlock were still
with us, so that he could comment on this present debate.  Not that I think
he would completely agree with me, but his insights were such that I would
take his opinions and criticisms more seriously than any others.  It was no
surprise that Ernst Mayr choose him to co-author the 2nd edition of his
systematics textbook.
                       -------Ken Kinman

>From: Richard Jensen <rjensen at SAINTMARYS.EDU>
>Reply-To: Richard Jensen <rjensen at SAINTMARYS.EDU>
>To: TAXACOM at USOBI.ORG
>Subject: Re: cladism's greatest weakness
>Date: Tue, 21 Sep 1999 11:51:39 -0500
>
>On Tue, 21 Sep 1999, Tom DiBenedetto wrote:
>
> > >No, ancestral species do not have to
> > >disappear (it is not a convention), but given the data sets, we seldom
>find
> > >a sister branch (as a computational tool, mind you) with no syn- or
> > >autapomorphies (so practically speaking ancestors disappear even if the
> > >speciation event that destroys them is just gradual change).
> >
> > This discussion is totally bound up in the subtlties of what you
> > consider a species to be. I dont know of any cladists who accept
> > Hennigs notion about ancestral species going extinct. Speaking just for
> > my self, it has always seemed pretty clear to me that when a
> > species-level taxon diverges (whether through "budding" or an even
> > division), the taxon (the lineage) becomes a higher taxon (becomes a
> > diverged, i.e. a more complex lineage). If we sent a colony off to
> > Mars, and they became reproductivly isolated, then the taxon Homo
> > sapiens would no longer be a species level taxon, it would refer to a
> > more complex lineage, and would be a higher taxon. Nothing has "gone
> > extinct" or disappeared.
>
>Given that you have used a specific criterion in your example
>(reproductive isolation), then I would argue that the taxon Homo sapiens
>is still a species (those on Earth), and those on Mars represent a new
>species of Homo (H. ares?).  Those on Earth still behave as a single taxon
>consisting of a large number of reproductively compatible individuals.
>
>I don't see the necessity of raising H. sapiens to a higher taxon.  As you
>say, nothing has gone extinct or disappeared.  If a have a species, and
>nothing goes extinct or disappears, then I still have a species.
>
>Richard J. Jensen      |   E-MAIL: rjensen at saintmarys.edu
>Dept. of Biology       |   TELEPHONE: 219-284-4674
>Saint Mary's College   |   FAX: 219-284-4716
>Notre Dame, IN  46556

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