genetic and morphological systematics

Richard.Zander at MOBOT.ORG Richard.Zander at MOBOT.ORG
Fri Jan 13 10:27:43 CST 2006


Well, those quotations, John, are not particularly impressive, since they
are merely cautionary, which is of course always acceptable in science, but
without giving particular reasons for the caution then the argument is
vacant and not instructive. 

Molecular studies are supposed to be better than morphological studies in
that the data is sufficiently abundant that it can be used in a statistical
context. Unfortunately the requirement that the data be (at least mostly)
independent and randomly distributed is doubtful. Certainly gene data (used
to get deep branch information because the gene sites mutate slower) is
subject to selection, even synonymous codons are subject (sometimes) to
codon bias and this is often not tested for. Non-coding sites commonly give
the same results as coding sites, so what does this suggest about non-coding
sites? 

For salient problems with statistics and methods that affect at least some
published cladograms, see
http://www.mobot.org/plantscience/ResBot/Phyl/Unaccounted.htm

Phylogeneticists are entirely happy with their speculative studies, and
multiple assumptions apparently do not faze them. Taxonomists and
biogeographers who want to use speculative phylogenetic analyses as a basis
for classification or distribution analysis need reliable results. 

______________________
Richard H. Zander
Bryology Group, Missouri Botanical Garden
PO Box 299, St. Louis, MO 63166-0299 USA
richard.zander at mobot.org <mailto:richard.zander at mobot.org> 
Voice: 314-577-5180;  Fax: 314-577-0828
Websites
Bryophyte Volumes of Flora of North America:
http://www.mobot.org/plantscience/bfna/bfnamenu.htm
Res Botanica:
http://www.mobot.org/plantscience/resbot/index.htm
Shipping address for UPS, etc.:
Missouri Botanical Garden
4344 Shaw Blvd.
St. Louis, MO 63110 USA


-----Original Message-----
From: John Grehan [mailto:jgrehan at SCIENCEBUFF.ORG]
Sent: Thursday, January 12, 2006 1:10 PM
To: TAXACOM at LISTSERV.NHM.KU.EDU
Subject: [TAXACOM] genetic and morphological systematics


With the orangutan-human evidence of morphology in mind, finally, a
molecular geneticist (Marks 1994 - American Journal of Physical Anthropology
94:59-79) making some sense:

 

 

"The history of biological anthropology shows that, from the beginning of
the 20th century, grossly naïve conclusions have been promoted simply on the
basis that they are derived from genetics, without having been fully
thought-out."

 

"When molecular and morphological data disagree, both must be re-examined
carefully, for genetics has been used irresponsibly as a form of scientific
validation, both in American society and in American science."

 

"It does not follow, though, that any data provided by genetic analysis are
more fundamental, and therefore more credible, in the analysis of
evolutionary patterns."

 

"The genotype has different properties from the phenotype, and one can
hardly rank as inherently superior or inferior two such phenomenologically
distinct kinds of studies."

 

"[The genotype/phenotype distinction]...provide an independent test of
phylogenetic hypotheses...Here, corroboration is valuable, but discordance
is difficult to interpret."

 

"Molecular evolution has not "provided a 'magic bullet' for phylogeny".

 

The conclusions of molecular genetics "need to be carefully weighted and
integrated, not blindly obeyed"

 

"The thoughtless use of genetics has never done anyone any good, and it
seems unreasonable to expect it to be of value in contemporary physical
anthropology."

 

"The distinction of note lies not in molecular-vs.-morphological data, but
rather, in well-executed research and well-reasoned conclusion, vs. their
opposites."

 

John Grehan

 

 

Dr. John R. Grehan

Director of Science and Collections

Buffalo Museum of Science1020 Humboldt Parkway

Buffalo, NY 14211-1193

email: jgrehan at sciencebuff.org

Phone: (716) 896-5200 ext 372

 

Panbiogeography

http://www.sciencebuff.org/biogeography_and_evolutionary_biology.php

Ghost moth research

http://www.sciencebuff.org/systematics_and_evolution_of_hepialdiae.php

Human evolution and the great apes

http://www.sciencebuff.org/human_origin_and_the_great_apes.php

 

 




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