paraphyly

Thomas Pape thomas.pape at NRM.SE
Mon Jun 16 16:56:19 CDT 1997


At 14.37 1997-06-16 +0000, Marc Sosef wrote:

>Anyone who discusses monophyletic
>classifcation and uses Linnaean caterogies does, in my view, not deserve
>further attention.

So, with the risk of not deserving further attention.....

Please let us not confuse shortcomings of nomenclature (communicating
results) with shortcomings of methodology.

It seems to me that the current thread (and to some extent Marc Sosef's
paper in Taxon 46) puts all to much emphasis on species.

Species are often referred to as the ultimate 'unit of evolution', with
great problems when it comes to 'ancestral species', etc.

But they are not. Species cannot be units of evolution for the simple reason
that species cannot replicate. Considering a speciation as a replication is
vague -- at the very best.

This has already been touched upon by Bengt Oxelman, who wrote:
>
>confusion of species as taxa (Linnean
>categories) and species as evolutionary units.

and later elaborated:
>
>..it should be very clear that they [taxa] do not participate in evolution
>themselves, they are the result of evolution. The 'thing' (singularity,
>system of replicators) that actually participitates in evolution needs
>another concept, entirely decoupled from Linnean categorical ranks, and it
>has nothing to do with taxonomy.

Genes - however defined - are what replicates. Shifting the discussion to
the level of genes will in itself not be an ultimate solution as even genes
may be characterised as 'ancestral' and as such be 'budding-off' daughter
genes, 'hybridise', etc.

Still, organismic evolution is basically caused by differential survival of
replicates, and the replication is by and large strictly hierarchical. This
is probably why our hierarchical models work so well.

So, rather than take a step backwards pleading for the acceptance of
paraphyletic supraspecific taxa, I would suggest that we try harder to match
Nature's hierarchy (including reticulations between 'species') in our
classifications.

Regards,
Thomas Pape


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