different taxonomies, Re: Farewell to Species - reticulation

Thomas DiBenedetto TDibenedetto at DCCMC.ORG
Wed Feb 16 09:20:45 CST 2000

Sorry this will be a bit brief, and I wont be able to follow up, for I will
be out of town again for a week,,,

Thomas Schlemmermeyer wrote:
....you admitted that there are whole subdisciplines of biology which
proceed without evolutionary perspective.
...Why should we bother about phylogeny? Phylogeny in the traditional sense
is the search for rooted trees. Rooted trees however are not part of purely
descriptive taxonomy, as they require aditional knowledge from paleontology,
embryology and geology. As I already tried to put clear, the morphological
systematist who works, usually, with the alfa-taxonomy of a small group may
put up unrooted networks at most. But it does not behoove to him to
establish phylogenies, as, as you yourself remarked, this would be outside
empirical science.
One may not make immediate reference to evolution when describing a new
species, but the instant that one wishes to place that species in any sort
of a context (including, for instance, choosing its generic name) then one
does need to understand phylogenetic principles. I doubt that there really
are any taxonomists who never aspire to say a word about where their new
species might fit in relation to other species.
Furthermore, and most importantly, I did not say that establishing
phylogenies is outside of empirical science (how on earth could you imagine
I would say something like that?). I said that the specification of
ancestor-descendant relationships are outside the purview of empirical
science. Ancestry is a very specific type of relationship; far more specific
than sister-group relationship. To say that two groups are sister-groups is
merely to say that they are more closely related to eachother than either is
to any third group. We can use the empirical data of character distributions
to reach this conclusion, since the shared presence of derived characters is
evidence of exclusive common ancestry. But a claim of ancestry would entail
the assertion that one species was transformed into another. There is no
pattern in character distributions which can distinguish this type of
relationship from more general sister-group relationships. So we can
speculate about ancestry, and we can find evidence to disprove a claim of
ancestry, but there is no type of evidence to indicate such a relationship.
Much of post-Darwinian, pre-Hennigian systematics was (unfortunatly)
focussed on the attempt to find ancestors. There is a lot of intellectual
baggage that has been aquired along the way, including influences on
"traditional" views in taxonomy. I recognize that stability has some value,
but nonetheless, I dont think we should shy away from incorporating and
integrating all that we have learned into our taxonomies. The framework of
our taxonomy dates from pre-evolutionary times, and has been influenced by
the ancestor-searching phase of our history. At some point in the future it
will be fully consistent with an evolutionary perspective, as well as be
reflective of the real empirical evidence that underlies the particular
hypotheses. I dont see any reason not to fully engage in the debates that
will create that new system. I find it to be fun, and a challange, but maybe
I am just wierd....

Tom DiBenedetto
tdib at dccmc.org

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