Ban the fungi imperfecti.......

David Holdom d.holdom at ctpm.uq.edu.au
Wed Feb 7 11:56:15 EST 1996


In article <4f47g4$41b at agate.berkeley.edu> David Geiser <dgeiser at mendel.berkeley.edu> writes:
>From: David Geiser <dgeiser at mendel.berkeley.edu>
>Subject: Re: Ban the fungi imperfecti.......
>Date: 5 Feb 1996 06:18:44 GMT

>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?

>>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.


>>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 can rear the caterpiller to the adult stage.  The same developmental 
sequence does not always occur for fungi.  For example, as far as I am aware, 
the sexual stage of the insect pathogen _Metarhizium anisopliae_ has never 
been observed in the lab or field, despite thousands of infected 
insects collected. and thousands of cultures obtained and studied over a 
hundred years or more.  It would be vey nice to place the Deutermycetes where 
they all belong, but right now we simply do not know that for many species,  
and so cannot do this in a consistent way. 

>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?

 IMO DNA technology is a powerful and vauluable tool, but it still has a way 
to go before we can interpret results reliably.  The variation in 
_Metarhizium_ for example is astonishing.  It is more than a matter of "just" 
running their ribosomal DNA.  There are some huge complexes to be worked out.  
maybe in 20 years, resources permitting.......................


>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.

exactly

>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?

I agree

>Dave Geiser

Dave Holdom



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