Well, as for the species concept .... not all folks agree with this
no-concept of species. Actually, most persons agree that species DO exist
in nature. They are are potentially of actually interbreeding goups of
individuals, reproductively isolated from other similar groups. This is
just one of the several definitions available. And we (I belong to such
group of believers) agree that Evolution proceeds by successive
modification and subdivision of species.
The fact that there are many exception is not a fault of Nature but is due
to his (of Nature) attitude not to adapt to ALL our conceptual boxes;
instead we pretend that once we create a definition, a concept, a scheme,
Nature fits that box perfectly and constantly. But Evolution is dynamics
thus ....

We must totally agree with the fact that DNA, morphology, ecology etc.. are
all features that must be carefully analysed and scrutinised in each
particular group to score the relative importance of (e.g.) radula vs.
protoconch, or genital apparatus vs digestive system. Actually, DNA is a
very powerful tool in revealing patterns of relationships among the
animals, but also in this case caution must be used.
I would distinguish between the methods (parsimony, maximum likelihood,
overall similarity etc...) and the object of analysis (characters from
morphology, allozymes, DNA etc....). Thus DNA is NOT like cladistics: DNA
is a molecule that can be a good or a bad character (then it is LIKE
morphology), while cladistics is a methodology (or a conceptual and
theorethical framework) for the analysis of character evolution.


At 12.23 07/06/02 -0600, Conchologists of America List
<[log in to unmask]> wrote:
>A species is an artificial box we have constructed to aid our understanding
>of the world around us.  I believe Tucker Abbott once said (grossly
>paraphrased here) that a species is what a local inhabitant recognizes as
>different and set apart from other local animals and plants - it looks
>different.  There is no true, always 100% correct test.  There seems to be
>an exception to every rule used to determine species.  Sorry to sound a bit
>preachy here - but this subject hits a nerve.  I have spent the last few
>years working on the Neritidae - a family that experts list has having 50
>species while other experts say 250!


=========================================================
Marco Oliverio - Evolutionary Biology PhD
Research Scientist

Dipartimento di Biologia Animale e dell'Uomo
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