[Taxacom] very nice opinion article in today's Zootaxa

James Whitfield jwhitfie at life.illinois.edu
Fri Sep 30 16:57:40 CDT 2011


> Or are we to believe that non-coding traits are evolutionarily
> significant beyond tracking genetic continuity and isolation events?
>

So are you saying that we should always use traits under strong selection
to determine the phylogeny of organisms? This is exactly the complication
of using morphological traits for phylogeny - we do not know whether we
are tracking actual phylogeny or local adaptation.  Both underlying causes
are fantastically interesting to investigate, and evolutionarily
significant, but only one of them should be used for phylogeny and
classification, I'd say. The other is very interesting to investigate once
we know the phylogeny.

And yes, I would agree that "total evidence" without any underlying
rationale as to the hierarchical utility of characters is not a foundation
for phylogenetic study. As they used to say as a critique of phenetics,
"garbage in, garbage out". Use as much data as you can but DO think a bit
about whether the data are appropriate for the question you are asking. If
not, you have every reason to exclude them.

Having said this, I think the traditional way of examining specimens for
revisionary work on species works pretty darned well in most cases - it
just does not always (maybe even usually) form a basis for phylogenetic
study.  The goals of character selection are (and should be) different for
diagnosis and phylogeny.


> Perhaps I might have inflated my rhetoric a bit, but I got some
> discussion going.
>
> We DO have an understanding of trait distributions in alpha taxonomy,
> enough to fairly well delimit taxa. Right? Even in flowering plants,
> descriptions indeed have some empirically based distribution of traits,
> even if extended through analogy.
>
> I submit, still, that a 95% or 99% credibility support distinguishing
> two molecular lines do not support two different distributions of
> evolutionarily significant traits, unless you eschew total evidence as a
> logical foundation for scientific study (a la Fitzhugh). They may be
> different samples from the same distribution of evolutionarily
> significant traits.
>
> Or are we to believe that non-coding traits are evolutionarily
> significant beyond tracking genetic continuity and isolation events?
>
>
>
> * * * * * * * * * * * *
> Richard H. Zander
> Missouri Botanical Garden, PO Box 299, St. Louis, MO 63166-0299 USA
> Web sites: http://www.mobot.org/plantscience/resbot/ and
> http://www.mobot.org/plantscience/bfna/bfnamenu.htm
> Modern Evolutionary Systematics Web site:
> http://www.mobot.org/plantscience/resbot/21EvSy.htm
>
>
> -----Original Message-----
> From: Peter Stevens
> Sent: Friday, September 30, 2011 4:11 PM
> To: James Whitfield; Richard Zander
> Cc: taxacom at mailman.nhm.ku.edu
> Subject: RE: [Taxacom] very nice opinion article in today's Zootaxa
>
> Indeed, thousand of specimens/species/thousands of obseervations???. For
> fl. pl., this would simply be inflated rhetoric.  Admittedly, I don't
> work on mosses, so no possibility of scoring cell characters for all
> specimens, but most morphological characters (flower; fruit) are scored
> from relatively few specimens, and when you get into anatomical (inc.
> seed anatomy), germination, pollen, etc., and chemical characters, then
> the sampling may be no better than molecular studies. And to what extent
> might we have actual specimen-based information for these thousands of
> observations?
>
> P.
>


-- 
James B. Whitfield
Department of Entomology
320 Morrill Hall
505 S. Goodwin Avenue
University of Illinois
Urbana, IL 61801
http://www.life.illinois.edu/whitfield





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