papulospores and my sincerest apologies

David Geiser dgeiser at mendel.berkeley.edu
Sat Nov 9 12:23:43 EST 1996


In article <55qlkp$o58 at bubba.NMSU.Edu> Peter Herman, rpeter at nmsu.edu
writes:

>If the structure is asexual, there is no reason to suspect a 
>modified cleistothecium.

I really don't know if it's reasonable to suspect that a papulaspore
is derived from a cleistothecium.   However,  I do think it's
reasonable to suspect that certain asexual structures are.  Two
examples from the Trichocomataceae:  Aspergillus flavus,  which
produces sclerotia,  seems to be related to Petromyces alliaceus
(see Peterson,  S.W., 1995 Mycol. Res. 11: 1349-1355), which produces
cleistothecia in stroma that look quite like the sclerotia found in 
A. flavus and its relatives.  In fact,  P. alliaceus was first
described as sclerotial,  until Malloch and Cain (1972;  Can. J.
Bot. 50: 2613-28) found ascospores;  in describing Eupenicillium
and its asexual relatives,  Pitt (1979;  The Genus Penicillium,
pp. 41) mentions that some asexual species produce immature
cleistothecia that don't go on to produce ascospores,  and that
these structures are termed sclerotia.

Perhaps I'm making too big a deal of these examples from this
group,  but my point was that if Papulaspora is related to
cleistothecial ascomycetes,  it may be that the papulaspore
is a modified or vestigial cleistothecium.  Again,  I don't
know enough about Papulaspora to say whether or not this is
reasonable.

  The problem with sorting things out is 
>the relative simplicity of fungal thalli.  If a fungus is 
>producing a thick-walled resistant structure, be it sexual or 
>asexual, there are a limited number of patterns it can follow to 
>make such a structure from hyphae.  When you look at the cell 
>arrangements and modifications involved in cleistothecia, 
>parathecia, apothecia, pseudothecia, pycnidia, sclerotia and 
>stromatic tissues, they can look quite similar, though the 
>structures can vary a lot in gross appearance.

Yes,  and this is why I think molecular phylogenetic analyses
are helpful in sorting out these difficult morphological questions.
That said,  it's amazing to me how well the morphologists have done 
inferring relationships,  considering how little they have to work 
with.


Dave Geiser



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