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

[Richard Zander]

Ken:

Congruence of molecular and morphological studies is often not to be
expected. Any organism that finds its morphology in stasis (hundreds of
thousands or millions of years) will have its non-coding DNA change.
Thus, such taxa group with other taxa retaining primitive traits in
morphological studies, but have divergent molecular traits. If such taxa
have generated daughter taxa, they will group, incongruently, with more
advanced taxa in molecular cladograms.

You say " I'm not saying that Richard Zander is guilty. . . "   My
stance is that optimality using numbers is impossible in an np-complete
study, and since parsimony (heuristics) and Bayesian (MCMC) analyses use
heuristics, so do alpha taxonomists. One heuristic is to weight
conservative morphological traits.  

Quality in morphological terms are conservative traits, i.e. those
refractory to adaptation. These are effectively used to group species
into higher ranks. 

It is only amazing that alpha classification of perceived evolution, the
last being mostly sequential generation of one taxon from another,
actually often matches the strict nesting of molecular clades. 

R.

 

* * * * * * * * * * * *
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: taxacom-bounces at mailman.nhm.ku.edu
[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Kenneth Kinman
Sent: Friday, September 30, 2011 9:36 PM
To: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] very nice opinion article in today's Zootaxa

      I think that this thread demonstrates that weighting characters
(especially molecular vs. traditional morphological) to achieve maximal
results is increasingly important, but often our understanding of how to
do so (that maximizes true phylogenetic signals in particular) is still
often poorly understood (and our ability to do so properly is a science
still in its infancy for many taxa, like it or not).                
      Depending on the taxon involved, morphology may need to be weighed
more heavily than molecular (especially in the interrim when molecular
data is limited).  But as more whole genomes are added into the mix,
molecular data will become more important, but how to weigh different
subsets of molecular data will still be an issue.   
     In any case, I find it somewhat disconcerting when I hear it
boiling down to a numbers game, as though quantity necessarily trumps
quality.  I'm not saying that Richard Zander is guilty of this
(sometimes quantity can win out beyond expectation), but I clearly do
find John Grehan's number games (based ONLY on morphology) extremely
distressing.  There is no balance at all when your database relies only
on morphology (dismissing the molecular data without offering any
opposing molecular data that is congruent with the morphological data
that is being given so much weight).  That is quantity over quality in
the extreme in my opinion.          
       However, I must admit that the orangutan-hominid morpholiogical
similarities still makes me seriously question the quality of the
molecular data (thus far) supposedly supporting an exclusive
chimp-hominid clade. That's why I think an exclusive chimp-gorilla clade
is a serious alternative possibility (but which has only minor molecular
support at present, at least the way in which the molecular data has
been interpreted thus far).  In the end, I believe that quality will win
out over quantity, but that what characters (morphological or molecular)
have the highest quality is often something that we don't really
understand very well.  Homoplasy (molecular or morphological) is still a
huge problem that is still a huge problem and will provide grist for
continued debate for many years to come.  My view is that:  Quantity
only indicates quality when they are consistently congruent (both
molecularly and morphologically).  Otherwise, more data is needed.    
              -----------Ken Kinman