Ban the fungi imperfecti.......

David Geiser dgeiser at mendel.berkeley.edu
Mon Feb 5 01:18:44 EST 1996


In article <4f1gpq$gdq at vixen.cso.uiuc.edu> Eric Grunden,
egrunden at prairienet.org writes:

>Does anyone else feel that the existence of the so-called
>Deuteromycetes is unscientific and many times redundant?

Yes.  In fact,  I think that even most supporters of the
Deuteromycetes would agree,  to some extent.

>After all, these fungi all have (or have had) sexual states
>and so should be placed where they properly belong to best
>demonstrate their phylogenetic relationship to other fungi.

This is exactly the problem.  First of all, the sole purpose of 
taxonomy isn't to demonstrate phylogenetic placement of taxa;  some 
would argue that this is not the purpose at all.  The purpose of 
taxonomy is to provide a framework for understanding biology and 
identification,  and phylogenetic placement may not be the most
useful way of doing that.  I am a big supporter of taxonomic schemes
that reflect phylogeny,  but there is more to it than just making
the trees and circumscribing taxonomic groups on that basis.

>I'm at a loss to understand what their placement in a grab-bag
>class teaches us, other than their sexual states are rarely
>observed.  Big Deal! If the caterpillar state of a certain
>butterfly is rarely observed, we don't place the butterfly
>in a different classification.

You have to realize that taxonomy has been going on for centuries 
and there is an important historical component to it.  The current
system has been in place for a very long time.  Placing all 
of the  deuteromycetes in other genera would be a mess,  as it would 
make the 100+ years of literature using the old names obsolete. If you 
were to change everything today,  all of the pre-1996 literature 
would use one set of names,  all future literature another.  Wouldn't 
THAT be confusing?

Plus,  people don't like to change the names they use,  and for
good reason.  Non-taxonomists don't like it when someone comes
along and changes the name of the research organism they've been
working on for thirty years.

Now,  there are provisions for transferring the deuteromycetes
into other groups,  and there always have been.  Personally,  I'd
love to see the deuteromycetes integrated based on phylogentic
information.  But there are some major sticking points to doing
it.  You will find many of the pros and cons described here:

The Fungal Holomorph:  Mitotic, Meiotic and Pleomorphic Speciation
in Fungal Systematics.  1993  D.R. Reynolds and J.W. Taylor,  eds.
CAB International,  Wallingford, UK.

 Help me out here, I'm not
>trying to start a flame-war with the deutero-people, just
>trying to understand why such an unscientific classification
>continues to persist.

Think of taxonomy as a language.  Even with the deuteromycetes,
it's more logical than,  say,  English.

Can't we just run an analysis on their
>ribosomal DNA and place them where they belong?

Is rDNA going to tell you the phylogenetic truth?  Which isolates
are you going to run?  How many per species?  Who's going to pay
for it?  Are you going to run parsimony on every species all at once? 
Wait, you can't:  you'd better choose taxa.  Which taxa are you 
going to choose?  What if the ITS gives you one answer and the
mitochondrial small subunit gives you another?  These are not 
unassailable barriers by any means,  but it's not as simple as
running an rDNA analysis and getting a clean answer.

Besides,  what are you going to do about the keys?  What if some
kind of "artificial" classification system is easier to use for
identification than a phylogenetically-based system?  Is the
phylogenetic system better?

I'm not saying you're wrong;  in fact,  I don't like the
deuteromycetes and would like to see them integrated.  But it
would be a major task to do so.  In my opinion,  we have more
important things to do first,  such as going out and finding the
~95% of the fungi we don't even know about, and understanding the
nature of fungal species and populations.  How can we create
ANY scientific taxonomic system based on only ~5% of the species,
and when we don't even know what a species IS?


Dave Geiser



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