Are species real? (taxa and taxities)

Guido at Guido at
Wed Apr 12 18:19:12 CDT 2006

Michael Lee wrote:

> I read my son a children's
> story in which a girl is listening to a roaring waterfall.
> Then she returns home, and the sound of the waterfall gets
> more and more faint.  Then "suddenly" she realizes that she's
> crossed "an unseen line" and can hear the waterfall no more.
> If she employed advanced technology, perhaps she could still
> hear the waterfall my amplifying the sound waves.  But that's
> not the point.  The point is that SHE cannot hear the sound
> anymore- it isn't detectable to HER anymore.

This illustrates well that in defining an organism (drawing species lines) 3
elements are involved: 1. the organism, 2. the observer (with his skills and
dogmas), 3. the tools (be it a magnifying glass or an electron microscope).
Features of the 3 elements will influence the definition (the species lines).
For that reason we will never be able to find a definition that is purely
organism dependent (and not also observer and tool dependent). And we may debate
for many, many years whether species are real...
However there is an alternative approach...
I consider any taxon (including a species) as man made construct, because it
taxonomically formalized. On the other I call the underlying entity the
'taxity'. It exists independently of the presence of any observer. What we do in
taxonomy is trying to catch (= formalize) taxities in taxa. With progression of
science the congruence of taxon and its taxity become larger. Sometimes we are
completely wrong and assign different taxa to the immature and mature form of
the same taxity. And due to the lack of material I'm sure our early hominid taxa
are without doubt a faint reflection of their taxities. And probably the
congruence between some taxa and their taxity will never be more than say 90%
because there is some overlap in the tails of the Gauss curve by which we may
represent their overall variation.
What is real are 'taxities' and what we talk about are 'taxa'

Guido Mathieu,
Peperomia Research Group
Department of Biology
Ghent University
K.L. Ledeganckstraat 35,
B-9000 Gent. Belgium

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