Spores - THE definative taxonomic feature??

Lorelei Norvell lorelei at TELEPORT.COM
Wed Feb 21 11:57:28 EST 1996


	While many taxonomists maintain that one species can be delimited 
from another on the basis of one single good character, most will agree 
that one cannot necessarily identify a species on the basis of one 
character alone.  You are correct in feeling that total reliance on a 
single character may be foolhardy, particularly with the advent of 
molecular techniques.  
	The problem is particularly vexing in taxa with relatively few 
characters.  But it strikes me that if you have a form which grows under 
conditions and exhibits a growth morphology completely different from a 
second form, the two forms are different taxa (whether forms, varieties, 
or species) even though they share spores of identical size and shape.
	Unfortunately, you have correctly recognized that you must accept 
the "default" identification.  Or check the DNA (if you are not 
proficient in RFLP/RAPD techniques, you might have a friend who could do 
it for you ...  comparing two isolates is a relatively inexpensive and 
speedy procedure for someone already set up).  A quick check _might_ 
reveal genetic differences.  
	Of course even if you were to show such differences, you still 
would not know whether you were dealing with _specific_ differences.

	Incidentally, this is why many people end up in taxonomy -- 
through default!

	Good Luck.

Lorelei


On 21 Feb 1996, R.N. Weinstein wrote:

> What do you all think?:
> 
> Is there a consensus that spore SIZE, within a range, and spore SHAPE is 
> enough to be the last word in species identification?  This seems to be the 
> current state of affairs in fungal taxonomy.  Is this system a relic, or 
> is it perhaps just a matter of it being the best system around by default?
> 
> I have isolated a fungus from Antarctic soils which was initially identified 
> to genus Humicola.  This fungus appears to be truly psychrophilic, 
> growing so far at temps as low as -2 C but not at temps above 20 C.  
> Submitted for a more precise identification, it was identified as Humicola 
> fuscoatra.
> 
> We then obtained a culture of H.fuscoatra and found that its 
> temperature/growth range was the opposite of my isolate: it did not grow 
> at +5 C, but grew robustly at 25 C.  Its growth FORM (in a petri dish) 
> was very different from mine: H. fuscoatra was white and fluffy (lots 
> of aerial mycelium); mine dark and swirly growing into the agar.
> 
> However, according to the institute doing the identification, it all 
> comes down to spore size and shape.  And so, without using molecular 
> techniques and doing a thesis's amount of work to prove a difference in 
> species, this appears to be the answer I must settle for.
> 
> Does this seem right?  Opinions please!
> 
> 
> Rick Weinstein
> University of Cambridge
> 

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