[Taxacom] morphology and molecules again

[John Grehan]

My attention was drawn to this paper by th press release
http://www.sciencedaily.com/releases/2009/04/090428171004.htm:

 

In which it was said:

 

"During a seminar at another institution several years ago, University
of Chicago paleontologist David Jablonski fielded a hostile question:
Why bother classifying organisms according to their physical appearance,
let alone analyze their evolutionary dynamics, when molecular techniques
had already invalidated that approach?

 

With more than a few heads in the audience nodding their agreement,
Jablonski, the William Kenan Jr. Professor in Geophysical Sciences, saw
more work to be done. The question launched him on a rigorous study that
has culminated in a new approach to reconciling the conflict between
fossil and molecular data in evolutionary studies."

 

Scientists using molecular techniques assert that genetics more
accurately determines evolutionary relationships than does a comparison
of physical characteristics preserved in fossils. But how inaccurate,
really, were the fossils? Jablonski and the University of Michigan's
John A. Finarelli have published the first quantitative assessment of
these assumed discrepancies in the Proceedings of the National Academy
of Sciences"

 

So here is the key question - how would the accuracy of morphologically
defined fossils be measured?

 

The press release goes on to say:

 

"No matter how they looked at it, the lineages defined by their fossil
forms "showed an imperfect but very good fit to the molecular data,"
Jablonski said. The fits were generally far better than random. The few
exceptions included freshwater clams, "a complete disaster," he said.



Jablonski and Finarelli (Ph.D.'07, University of Chicago), then decided
to push their luck. They looked at the fits again, but this time focused
on geographic range and body size. The result: a "spectacularly robust"
match between the fossil and molecular data.



Jablonski interprets the results as good news for evolutionary studies.
The work backs up a huge range of analyses among living and fossil
animals, from trends in increasing body size in mammal lineages, to the
dramatic ups and downs of diversity reported in the fossil record of
evolutionary bursts and mass extinctions.



"Our study also points the way toward new partnerships with molecular
biology, as we straighten out the mismatches that we did find," he
said."

 

So the press release ends a bit waffly, but the basic argument seems to
be that morphology can get pretty good answers when it matches molecular
results. If I am correct in that perception, then the paper just
continues to perpetrate the assumed superiority of molecular similarity.
That also seems to be the inference in the paper although the authors
sort of obscure their assumptions in this regard. They say "the strength
of the phylogenetic information in morphology-based taxonomies is
encouraging", but how does one know the information is strong - by its
match with molecular truth.

 

The paper ends with the usual molecular propaganda - "Increasing
availability of molecular data can help develop new approaches to
morphology-based systematics, by pinpointing characters that reliably
[!] capture phylogenetic relationships versus those consistently subject
to homoplasy...etc etc"

 

So there you have it. Molecular systematics continues to be propagated
as the holy truth of phylogeny. What never ceases to amaze me is how
phylogenetic morphologists, whether dealing with living or fossil taxa,
are so keen to prostrate themselves before this supposed molecular
authority.

 

John Grehan

 

 

Dr. John R. Grehan

Director of Science

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/research/current-research-activities/john-gre
han/evolutionary-biography
<http://www.sciencebuff.org/biogeography_and_evolutionary_biology.php> 

Ghost moth research

http://www.sciencebuff.org/research/current-research-activities/john-gre
han/ghost-moths
<http://www.sciencebuff.org/systematics_and_evolution_of_hepialdiae.php>


Human evolution and the great apes

http://www.sciencebuff.org/research/current-research-activities/john-gre
han/human-origins