Assumptions and reliability of solutions

[Paul Kirk]

Richard, your last point here is well taken - we should just use our eyes and trust our senses - often the organisms we study understand more about where they should be classified than we currently do. My best 'student story' here concerns a fungus as follows:

A genus of hyperparasitic fungi (mycoparasites; fungi parasitic on other fungi) had at the turn of the 19th century (one exception now known) very exacting host requirements - they could only parasitize members of a small order of soil microfungi in the Zygomycota. An observant French mycologist noted that a fungus described as a member of the Ascomycota could act as host for one of these parasites. He argued that this was very strong evidence, which he accepted, that the 'asco' was, in fact, a 'zygo', even though this fungus was morphologically unlike any known 'zygo' and lacked the diagnostic characted for the taxon - zygospores. Some 20 odd years later he was shown to have been correct when a species similar to the 'asco' was described with zygospores. Take home message of this story: the non sentient species we share this planet with are often better systematists than we are.

Paul Kirk
Mycologist
CABI Bioscience UK

-----Original Message-----
From: Richard.Zander at MOBOT.ORG
To: TAXACOM at LISTSERV.NHM.KU.EDU
Sent: 14/03/05 23:17
Subject: Re: [TAXACOM] Assumptions and reliability of solutions

Well, you can get decent bootstrap proportions from a morphological data
set, often, by restricting the number of taxa to a small monophyletic
group.
Since there are few characters, homoplasy outside monophyletic groups
makes
bootstrapping problematic.

But in any case, branch arrangments on a morphologically based cladogram
that are distant on the cladogram are commonly considered reliable.
Resolution using morphological data sets is apparently low.

My point in my post was that, reliability measures (bootstrap
proportions,
posterior probabilities) should be corrected for external assumptions.
After
correction, I suspect, molecularly based cladograms will have almost as
poor
resolution as the morphology based cladograms.

I might as well make another point here:
(1) you can struggle to find reliability measures for branch
arrangements,
or
(2) you can do some "biosystematics" (remember biosystematics?) like
common
garden or reciprocal transplant work (or whatever zoologists do that is
equivalent). It's too bad that work doesn't have the students or cachet
it
once had. Lot of potential there to solve taxonomic problems.

______________________
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: 314-577-9595
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: E. Parmasto [mailto:e.parmasto at zbi.ee]
Sent: Monday, March 14, 2005 4:41 PM
To: Richard.Zander at MOBOT.ORG; TAXACOM at LISTSERV.NHM.KU.EDU
Subject: Re: Assumptions and reliability of solutions


Richard Zander:
> The difference between a cladist and a non-cladist can be summarized
> in the following manner:
   etc., &c.
For me, the main difference is that probability /
reliability of the results of a cladistic study
(phylogenetic trees, resulting classifications, etc.)
may be somehow measured / characterized. What
about reliability of the results of a non-cladistic
study? Are there any good methods to evaluate the
probability of phylogenetic constructions /
hypotheses made by non-cladists (not including
pheneticists) ?
Erast Parmasto
******************