semi-holophyly clarified (was "generic oversplitting")

David Orlovich David.Orlovich at BOTANY.OTAGO.AC.NZ
Thu Jul 19 08:15:40 CDT 2001


Dear Ken and other interested parties,


>My classifications **ARE** continuously
>nested, but still allow an occasional semi-paraphyletic break in the tree of
>life at carefully selected major nodes (which usually precede very poorly
>understood sections of the tree).

I'm sure you know: poorly understood section of a tree could be
better understood by further research using a combination of research
techniques.  Poorly understood sections of trees are a stimulus for
further research and are the reason many people are interested in
evolutionary biology.  By giving nomenclatural stability to such
taxa, by accepting paraphyletic groups, it seems to me you're
admitting defeat in your endeavor to further understanding of
evolutionary relationships.  One could argue that nomenclatural
stability is good for end users - whoever they are - but we're not
here to provide a cheap fix for people - we're here to do
evolutionary biology.  Cladistics is a very elegant technique for
fitting data to a branching tree structure, but as I'm sure you know,
it is only as good as the data used to make the tree.  So, there will
always be more characters to measure, more DNA to sequence, more
ontogenetic studies to carry out, in order to progress further.  If
there was a need to have a system for 'flagging' paraphyletic groups,
it would be in use now and your time wouldn't be taken up advocating
the Kinman System.  Then you could spend more time doing fundamental
research to understand better the relationships between poorly
understood taxa that the Kinman System is trying to cover up with
stability.

David Orlovich.


>     A modified system makes it possible to incorporate both branching and
>divergence into a single classification, and at the same time provides much
>greater nomenclatural stability in poorly understood parts of the tree of
>life.   And it also sweeps away the perceived need to eliminate ranks or the
>notion that the whole Linnean System isn't worth the bother (it is not a
>dead or dying system if I have anything to say about it).  I understand the
>fundamental principles and goals of both sides, and believe that it is
>mainly stubbornness, inertia, and indifference which are standing in the way
>of bridging the differences.
>      A middle ground approach is possible (and if anyone says this is like
>being half-pregnant, I think I might tear my hair out).  A cladisto-eclectic
>system will almost certainly be widely adopted sooner or later, once the
>advantages become apparent to enough people (and it will probably snowball
>from there).  Until then, things will just slowly deterioriate.  In the
>meantime, I will continue to plant my hybrid seeds and explain their
>advantages to anyone who will listen.
>                 Rant over,  Ken
>*********************************************************
>>From: Thomas DiBenedetto <tdibenedetto at oceanconservancy.org>
>>To: 'Ken Kinman' <kinman at HOTMAIL.COM>, TAXACOM at USOBI.ORG
>>Subject: RE: generic oversplitting (heart of the problem)
>>Date: Wed, 18 Jul 2001 11:39:28 -0400
>>
>>-----Original Message-----
>>From: Ken Kinman [mailto:kinman at HOTMAIL.COM]
>>An Ashlockian approach, coupled with my simple convention for exgroups, is
>>almost certainly where we are going to end up eventually, so why put it off
>>and go through even more turmoil?
>>
>>I have never found the argument, that one's own particular point of view is
>>certain to win out in the end, to be very compelling (even when I find
>>myself resorting to it). I see no reason whatsoever to think that this will
>>be the case in this particular instance. The reason is rather simple. The
>>cladist's disdain for paraphyly is fundamental to the cladistic point of
>>view. This perspective is based on the goal of structuring our scientific
>>classification in such a manner that it mirrors what we accept as the
>>historical pattern of taxic divergence. It accepts that the historical
>>process has yielded higher groups that divide to form lower groups, forming
>>a contiuous inter-nested hierarchy. The notion of taking (e.g.) one group
>>of
>>the descendants of the ancestral reptile, and removing it from the natural
>>group formed by the all of the divergences of that ancestral reptile and
>>its
>>descendants, is an absurdity within the cladistic perspective. It runs
>>directly counter to the fundamental goal of cladistics, which is to
>>classify
>>in accordance with the historical pattern of lineage divergences.
>>I think that by now you should recognize that there is no compromise
>>available for this dispute. Either one accepts the principle that the
>>classifcation mirror the historical divergence pattern, or one doesn't.
>>Your
>>appeal to a "reasonable compromise" rings hollow for it is in fact nothing
>>but an appeal for your own perspective. Eclectic classifications do not
>>rule
>>out holophyletic groups, so your perpsective offers the virtues of
>>tolerance
>>and inclusiveness. In fact though, it simply asks cladists to abandon their
>>fundamental principle and goal. That is not going to happen.
>>I suggest that any further argument on this point be focussed on the very
>>simple question that is truly at issue. Should the scientific
>>classification
>>be aligned with our conclusions regarding how lineages have diverged, or
>>should our classification be only partly reflective of that pattern,
>>modified by other criterea as well. That has always been the real issue
>>between cladists and "darwinians". Paraphyly is a deriviative issue in this
>>dispute. Paraphyletic groups are an absurdity in the first perspective, and
>>they are probably a necessary feature of the second. It is a distraction to
>>argue about them when the real issue is even more fundamental.
>>
>>Tom DiBenedetto
>_________________________________________________________________
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--

Dr David Orlovich,
Ecology, Conservation and Biodiversity Research Group,
Department of Botany,
The University of Otago
PO Box 56,
Dunedin, New Zealand.

Telephone: (03) 479 9060 (international +643 479 9060)
Mobile: 021 133 9773 (international +6421 133 9773)
Fax: (03) 479 7583 (international +643 479 7583)
WWW: http://www.otago.ac.nz/botany/ and http://telperion.otago.ac.nz/erg/
email: david.orlovich at botany.otago.ac.nz




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