Subject: ED: Paleomycology?!...

From: [email-masked] ("Stephen P. Bentivenga")
Date: 24 Oct 1996 10:00:50 -0700

On 24 Oct 1996 03:40:37 GMT, [email-masked] (Eric Grunden) wrote:

>Is there a field of study that deals with the evolution
>of fungi? It seems that paleobotany only concerns itself
>with plants. Any good schools? What are the major changes
>in fungi versus extinct forms? What are some unusual
>characteristics found in primitive fungi that didn't
>survive? From what did fungi evolve? When? Which came
>first, plant roots or mycorrhizal fungi? Did the symbiosis
>start out as parasitism that some plants "learned" to
>survive? Were there fungi that specifically only decomposed
>dinosaur flesh? <--Perhaps the sexual states of some of the
>so-called imperfects (that's why we don't see the perfect
>states today)? Curious............

WOW!  Some pretty heady questions, most of which are yet unanswered.  So,
>from  the easiest questions first.... Yes, there is a field called
Paleomycology.  Fungi do not preserve well and are thus under-represented in
the fossil record.  However, we do know that fungi were present at least 500
million years ago (long before the Dinosaurs roamed the planet).  

Not many people do paleomycology since there aren't many fossils and there
really isn't tremendous amounts of money to do it.  Some very good work is
coming out of Dr. Tom Taylor's lab at the University of Kansas.  In the new
issue of Mycologia is a paper by Phipps and Taylor describing arbuscular
mycorrhizae from Middle Triassic fossils (co-occurring with Dinosaurs).
Other work from Taylor and his students demonstrate fossil mycorrhizal fungi
in the Devonian period (c. 400 MYA).  

Most of the other questions cannot be answered with any level of certainty.
Animals are more closely related to animals than to plants, so they may have
evolved from an ancestral cilliate.  The "fungal type of body" evolved
independently more than one time, giving rise to several groups that
traditionally have been called "fungi."  

Which came first, plant roots, or mycorrhizal fungi?  Well, the crude
"rhizoids" of ancients plants such as *Rhynia* are colonized by fungi that
look very much like extant mycorrhizal fungi.  Thus it appears that the
chicken and the egg evolved together.  Fossil spores of a mycorrhizal fungus
look virtually identical to the extant species *Glomus intraradices*,
suggesting the fungus may have changed very little (at least overtly) for
many millions of years.  Whether this ancient association was pathogenic or
mutualistic, no one can say.  Some scientists hypothesize that the symbiosis
evolved from a pathogenic relationship, while some speculate that it was
always mutualistic.  We will neveral know for sure.  Trying to reconstruct
400 million years of time with only a few scant fossils as evidence will
always be a guessing game.  

Hope this answered a few questions -- and maybe raised a few.  

- Steve Bentivenga

____________________________________________________________
                                
      ___/^,       Stephen P. Bentivenga, Ph.D.
     ;      ^'--.    Department of Biology & Microbiology
    :            -:    University of Wisconsin Oshkosh
   /              '--.   800 Algoma Boulevard
  /                  `\    Oshkosh, WI  54901-8640  
 :                    /  
 .                   / /',  
 {                   \/ /   Phone:  414-424-7088
  {_                   /   FAX:    414-424-1101
    ^\           UWO  ;   Email:  [email-masked]
      }            *  |     or:  [email-masked]
      \               | 
       |              |    
        |             |    
         (____________] 
____________________________________________________________