It's about NAMES, not clades (RE: Ashlock was treated badly)
tdib at OCEANCONSERVANCY.ORG
Wed Jan 9 13:20:08 CST 2002
From: Richard Pyle
Linnaeus devised his nomenclatural scheme before the
concept of evolution was widely understood (or perhaps even conceived). Some
time after Darwin's perspective of the origin of diversity gained widespread
acceptance, taxonomists began to assume that Linnaeus' hierarchical
nomenclatural scheme fit well with the hierarchically bifurcating pattern of
evolutionary history, and thus tended to focus their attention on using the
nomenclature to represent the evolutionary relationships. When cladistics
began to take over much of modern taxonomic thought processes, this tendency
transformed into dictum: "The Linnaean names SHALL strictly reflect
evolutionary relationships as we currently understand them to be!"
I have serious questions about this conceptual history, and on your
insistence that the issues is NAMES. I dont really see what the dispute
about names really is, it seems to me that the fundamental problem with the
Linnean system in an evolutionary context is the issue of Ranks. And this is
separate from names. Maybe I am missing something, but I dont really see why
Linnean names cause any problems in a cladistic system. I would abandon the
conventions on name endings that are associated with ranks, but beyond that
what is the problem? It is the ranks that are problematical - so I would
agree with the Phylocode abandonmnet of ranks, but it seems to me that one
doesnt need a whole new system in order to abandon ranks.
As to the history, I dont see that post-Darwinian taxonomists assumed that
L's hierarchical scheme fit well into evolutionary history. To the contrary,
I think that the general acceptance of hierarchical arrangements pre-Darwin
played a role in stimulating the idea of evolution -i.e. that the empirical
science of systematics seemed to indicate that there is an inherent
hierarchical arrangement to diversity which was in need of explanation
(Darwin's "hidden bond"). So taxonomists used hierarchy, and L's system
before the Darwinian period, during the Darwinian period, and continue to do
so today. The Linnean system "belongs to" the empirical science of
systematics, and I dont see why it cannot continue to be used as a vehicle
to communicate the empricial results of our studies.
Ultimately, this boils down to a tendency for
certain cladistic taxonomists to gain unwarranted confidence in their
phylogenetic hypotheses, so much so that they propose substantial
rearrangements in nomenclature. Another year's worth of investigation,
however, leads them to further rearrangements of nomenclature to reflect the
new interpretation. Multiply this by a bunch of years and a bunch of overly
confident cladistic taxonomists, and you end up with massive instability of
I disagree with this as well. My training was in morphological cladistic
systematics, and I never found instablility to be a problem. I was taught a
discipline in which one does not propose new classifications unless one has
completed a thorough revision of a taxon; an analysis that includes every
character that has ever been proposed for the group, a complete synonomy,
reference to all literature on the group etc. This is what the cladistic
"logic" demands, and has been explicitly advanced by the "total evidence"
movement. I see a massive instablility problem in modern systematics, but
does not come from cladistics per se, but rather from genetic systematists
(some of whom are cladists) - it is the bizarre assumption of many
sequencers that the results of an analysis of a short stretch of a single mt
gene produces results that supposedly trump hundreds of years of character
analysis of the group. This is an attitude that I sense will fade with time
as everyone realizes that the identity of a particular nucleotide is simply
one more character to be considered with all the others. In short, there is
nothing in cladistics that necessarily fosters instability - in fact I think
the case should be made that cladistic classifications, to the extent that
they seek to reconstruct the singular true history of taxic divergence, will
be more stable in the long run, especially as opposed to classification
schemes that are inherently based on subjective ranking decisions.
Even with strict
adherence to monophyly (sensu Hennig), a ranked nomenclatural scheme such as
Linnaeus' will always incorporate a component of subjectivity and arbitrary
decisions on the part of the taxonomist. As such, the Linnaean nomenclatural
system is imperfect for representing phylogenetic relationships.
What subjective or arbitrary decisions are you referring to?
Obviously, if the system was established
before the notion of evolutionary relationships even existed, then there
must be *some* function to the names *besides* representing evolutionary
Yes, the system has always been about delineating, identifying and naming
the species and groups of species (taxa) that an empirical analysis of
diversity yield. The notion of evolution and the processes of evolution are
inferred from this empirical base.
And in some cases, the non-evolutionary functions of nomenclature
can trump the evolutionary function, hence we still recognize the
monophyletic "Aves" as a distinct class from the paraphyletic "Reptilia"
(don't we?), because it serves a useful communicative function to do so.
What is this "we"? I certainly dont recognize Aves as a distinct class from
Reptilia. Aves is a subclade somewhere within Dinosauria, which is somewhere
within Archosauria, which is part of Reptilia. And I have never encountered
any problems in communication with this insistence (although it does
sometimes lead to interesting discussions!). I think that the Darwinian
application of the rank system is _nonsense_, and the sooner we simply stop
clutching on to it, the sooner everyone, including the general public, will
have a better sense of what our evolutionary history really was.
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