an answer to paraphyly

Robin Panza panzar at CLPGH.ORG
Sun Jun 15 10:08:53 CDT 1997


>As far as I understand it, after a speciation event, two entirely new taxa
>are described, if such an event could be witnessed. The "old" species they
>evolved from ceases to exist as far as cladistic methodology is concerned.
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Ah, but that's the point!  It has nothing to do with nature, just a byproduct
of a theory that is inadequate to describe nature.  If a population is
separated from the "parent group", it may be subjected to slightly-to-very
different environmental factors.  There's no reason for this to affect the
parent population, so there's no reason to the parent population to change.

        - a gravid female lizard gets washed away on flotsam that finally
grounds 'way downriver outside the species' range
        - a couple of birds get caught in a storm and end up elsewhere (another
island, another continent, whatever)
        - a change in a riverbed makes a swamp where the was none (or the other
way around), so one population of beetles now lives in a different enviromnent

None of these will have any effect on the parent population, no matter how much
or how little the colonists change.  Cladists must give the parent taxon a new
name, even though it hasn't changed, just because there is now a differentiated
offshoot somewhere.

Robin K Panza                           panzar at clpgh.org
Section of Birds, Carnegie MNH
Pittsburgh  PA  15213  USA




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