Phylocode, Cladistics and Eclecticism ...

[Byron J. Adams]

on 3/14/02 2:43 PM, Ken Kinman at kinman at HOTMAIL.COM wrote:

> The likelihood of a true sister group split (mother and daughter
> simultaneously evolving separate apomorphies) is very low, and the
> probability that two such true sisters would both evolve into higher taxa
> gets even more remote.  Mother-daughter relationships are the norm, and
> sister-sister groups are the rare exception.

Perhaps there is a non-metazoan bias here.  The only study I am familiar
with suggests exactly the opposite.*

Ken may be correct in asserting that at the moment in time when two lineages
split (become independent) they are indistinguishable, but if that is the
case, then it is epistemologically (methodologically) impossible to
determine this based on evidence (all the evidence favors the existence of
only a single lineage).  I think much of the confusion arises when we
conflate epistemology (HOW we delimit lineages) with ontology (WHAT lineages
are, i.e., their reality independent of human observation).

It is not until evolution produces autapomorphies that we are justified in
delimiting species.  Without them, how can one distinguish phylogeny from
tokogeny?  Even if we acknowledge the "messiness" or "fuzziness" of Ken's
'species', by the time evolution produces evidence of lineage independence
(speciation) we are forced to recognize that what once was a single lineage
is now two, and that each of these lineages, however fuzzy their origin,
have now become mutually exclusive, yet remain more closely related to each
other than to any other equivalent entity (aka sister taxa).

* Lynch, J. D. 1989. The gauge of speciation:  On the frequencies and modes
of speciation. Pp. 527-553 in D. Otte and J. A. Endler, eds. Speciation and
its consequences. Sinauer Associates, Inc., Sunderland, MA.

Byron
--
Byron J. Adams
University of Florida
Dept. of Entomology and Nematology
Natural Area Drive
PO Box 110620
Gainesville, FL 32611-0260