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Re: Paradoxically temporal



In a message dated 98-07-23 19:10:57 EDT, th81@umail.umd.edu writes:

<< >Is it for the same reason put forth by Chris Brochu,
 >that you also use the phylogenetic species concept
 
 Actually, I don't.  The species concept I use is something more like the
 traditional "Morphological" Species Concept (although I'd prefer to use the
 "Specific Mate Recognition System" Species Concept, but that really isn't
 testable with dead things...).  Actually, Horner's got some interesting
 things to say about species and species concepts in "Dinosaur Lives" and
 elsewhere. >>

I'd love to drive a stake through the heart of that Phylogenetic Species
Concept, one of the most ridiculous ideas to dribble out of cladistics
(poisoning the whole system, if you ask me). Imagine you have a population of
animals that becomes divided in two by, say, a river that keeps one group from
interbreeding with the other. The Phylogenetic Species Concept declares that
>at this point< the original species becomes extinct, and two daughter
species, both identical to the parent species, come into being. Talk about
>arbitrary<! And if the river dries up later, and the two populations merge,
what then? Two species going extinct and a fourth species created?

The time to declare that a new species has arrived is when a well-defined
evolutionary novelty appears in a population, even if (as is generally the
case) there is no associated cladogenetic split. Since all we have is
hindsight, morphology, and the fossil record for paleo-species, this is the
best we can do, as far as drawing lines between species goes.