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Naming Species #2

Mark Siddall mes at zoo.toronto.edu
Tue Mar 1 23:04:19 EST 1994

I have followed this thread for a while an dhave thought a fair bit
about the species question in protists with my own work.

My initial feeling is that the problem is intractable.  Unlike sexually
reproducing clades, in asexually reproducing taxa, phylogeny and 
tokogeny are the same thing.  As such, it is possible that the
members of a paraphyletic assemblage are identical in all respects.

The question of what should be a species then becomes one of opinion
rather than fact.  I doubt that anyone can give a compelling reason
why a given percent sequence dissimilarity should be reason for separating

In questions of pathology, it may be advantageous to distinguish "types"
either as strains or species to give the medical practitioner a way
of identifying whether or not there is cause for concern.  

I do think, however that any debate on the "reality" of whether or not
two or more isolates are really different species, whether based on
morphological distinctness, or on molecular distinctness, may prove to
be wholly misguided if we can't decide on what IS a species in the
first place.



   In every work of genius we recognize our own rejected thoughts;
    they come back to us with a certain alienated majesty.
                                                   -- Emerson

Mark Siddall                                     mes at zoo.toronto.edu
Department of Zoology
University of Toronto
Toronto, Ontario, Canada
M5S 1A1



   In every work of genius we recognize our own rejected thoughts;

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