Limits of cladistics?

["R. Irmis" <rbi@dana.ucc.nau.edu>]

I think, that the problem is not necessarily with cladistics per se, but
that we are dealing with partial remains of animals that have been extinct
for million of years or more.  Right now, I think cladistics is the best way
to determine phylogenetic relationships because it takes into account
evolutionary changes and states without as much human bias as a simple
morphological analysis.  Another present problem with cladistics is that
people use it to find relations of animals, but they still use simple
morphological analysis to define species and genuses of extinct animals.  I
feel we should be using cladistics here as well to decrease the amount of
human bias.

That said, I dont think that cladistics is necessarily perfect for modern
species because you have animals that are morphologically identical, but are
indeed distinct species.  In discussions with Dr. Ralph Molnar, he mentioned
that in Australia there are 5 species of kangaroos whose skeletons are
identical.  Only by knowing which species they are from would you know that
the skeletons are from different species.  Using excretions in extant
animals I think fits hand in hand with cladistics.  Its no different than
using DNA or analyzing unique proteins.  Perhaps, in modern cladistics, we
should use behavioral states as well? (has this been done?)

Regards,
Randy Irmis
-----Original Message-----
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Sent: Saturday, April 14, 2001 9:35 AM
To: dinosaur@usc.edu
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Subject: Limits of cladistics?


Jaime A. Headden wrote on 03/27/2001:

> I would not stake my reputation on a cladistic analysis -
> ever; but not also on a simple morphological or molecular
> analysis, either. A synthesis, perhaps, but not each individually.

 There's a report in Science regarding this in extant big cats. I haven't
had
time so far to go to the library at the local university and take a closer
look. But here's a (freely) translated report which appeared in the science
section of Süddeutsche Zeitung dated 04/03/2001.

 If you've got these problems of determing relationships with extant
species,
how much more does this apply for extinct species where you can do only a
cladistic analysis?

Cheers

Heinz Peter Bredow


Süddeutsche Zeitung, 04/03/2001

Related Scent

Zoologists use anal secretions of cats

Not only cats find out something about other members of their species when
sniffing scents of their anal glands. Scientists are also able to infer
relationships between big cats from these signal substances (Science, no.
291, p. 1861, 2001).

Up to now an analysis of characters of body and genetic makeup of puma and
cheetah, lion and tiger didn't allow it to reliably determine their
relationships.

Therefore scientists recently studied the composition of scents of anal
glands which are used by members of one species for e.g. signaling their
conception readiness.

By comparing the chemical cocktail of sixteen big cats they quickly found
out
how the species are related. They hope to be finally able to determine the
position of the american puma and the african cheetah in the phylogenetic
tree.