The attitrion of taxonomic expertise

James Lyons-Weiler weiler at ERS.UNR.EDU
Thu Oct 17 07:19:16 CDT 1996


Hugh D. Wilson wrote:

> If the systematics community is to contribute data that helps deal
> with various biodiversity problems, should we provide gene trees
> that place the Apiaceae (Carrot Family) in the Asteridae (which is
> interesting and available) or county-level mapping for US FWS-listed
> species of the Apiaceae (which is useful and not available)?

When this kind of thing happens (i.e., paraphyly in gene trees), any
number of explanations are possible, and some are more likely than others.
1.  the gene tree is wrong.  why?
                long branch attraction
                no phylogenetic signal (mutation saturation)
                alignment errors
                contamination
                misidentification of source tissue
2. the gene tree is right.  how?
                differential sorting of ancestral polymorphism

I submit that if phylogenetic systematists had the analytical tools to
distinguish between incongruence due to errors in phylogeny estimation and
more complex evolutionary processes, the death of taxonomic expertise
would be forestalled.  Imagine if the subset of gene trees that could
provide decent estimates of organismal phylogeny could be isolated.  The
study of character evolution on those types of trees would _help_ with
taxonomic expertise.  For now, we'll have to enjoy the musings of authors
as they explain why the gene tree looks so funny without critical tests of
these ad-hoc (tacked-on) explanations.


In addition, I raised the phylogeny of life symposium in Tucson, Arizona.
Part of the reason why molecules have overrun morphology (which is clearly
not dead!) is that statistical techniques have been devised to study the
pattern in molecular characters with some degree of sophistication.  I beg
your indulgence for a plug for the RASA measure of phylogenetic signal,
which can be applied without prejudice to morphological (discrete) and
molecular data.  Might we see the day when a gene tree is rejected because
the morphological data carries all the signal?

Please help yourself to RASA 2.0 at
http:/loco.biology.unr.edu/archives/rasa/rasa.html.

(macintosh only)

Web neophytes can mail a diskette to me at the address below and I'll be
happy to send the software by snailmail.

James Lyons-Weiler



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