[Taxacom] Justifying species or species concepts?

Bob Mesibov mesibov at southcom.com.au
Wed Feb 20 17:15:02 CST 2008


A middle road would be nice, but what we seem to have at the moment is a
range of variably well-worn paths (species concepts) in a dark forest.
It's not at all obvious where such paths cross, either.

At conferences I listen to presentations in which 'species' is possibly
the most frequently used noun. As with 'beauty', the meaning of
'species' is clear enough to the speaker/beholder, but the audience is
left to make its own judgements.

Many of the molecular taxonomic presentations demonstrate genetic
structuring in populations, which *may* be interpreted as the result of
restricted or recently absent gene flow. The presenter concludes by
saying this is evidence of the existence of cryptic species, i.e. if two
populations are not exchanging genes, then they have been sampled from
entities called 'species', defined as groups of populations which don't
exchange genes.

I also hear presentations in which sampled populations are grouped into
clades by (mainly non-molecular) character analysis based on parsimony.
The presenter concludes by saying there are enough differences between
clades to recognise by diagnosis several entities called 'species',
defined as diagnosably different groups of populations.

Both presenters then give their various entities Linnean names, which
introduces a third sort of 'species' (in my experience this is less
often done by the molecular-only workers, but maybe my experience is
biased).

Both presenters are interested in discovering diversity and
communicating what they find. The common coin for sharing knowledge of
diversity seems to be 'species', which is a familiar word but a very
slippery one. It could be argued that diversity in genetic structure can
be discovered and communicated without mentioning 'species' at all, in
the same way that a phylogeny of character descent can be adequately
documented without naming a single taxon, even at the terminals. It
could be similarly argued that diversity in character state combinations
can be discovered and communicated without mentioning 'species'.

Where's the middle road, if 'species' aren't realities to be discovered,
but terms of convenience to describe the results of very different
analytical procedures?
-- 
Dr Robert Mesibov
Honorary Research Associate, Queen Victoria Museum and Art Gallery
and School of Zoology, University of Tasmania
Contact: PO Box 101, Penguin, Tasmania, Australia 7316
(03) 64371195; 61 3 64371195
http://www.qvmag.tas.gov.au/mesibov.html
---





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