Help with taxonomy of protists

David J. Patterson paddy at EXTRO.UCC.SU.OZ.AU
Thu Aug 25 23:38:47 EST 1994


RE: YOUR QUERY ABOUT HOW DIFFERENT APPROACHES AFFECT CLASSIFICATION

THERE ARE THREE RECENT ATTEMPTS TO PROVIDE AN OVERALL CLASSIFICATION OF 
PROTISTS

CAVALIER-SMITH T 1993  KINGDOM PROTOZOA AND ITS 18 PHYLA.  
MICROBIOLOGICAL REVIEWS 57: 953-994.   THIS ONE RELIES HEAVILY ON SPECULATION

CORLISS JO 1994  AN INTERIM UTILITARIAN ("USER-FRIENDLY") HIERARCHICAL 
CLASSIFICATION AND CHARACTERIZATION OF THE PROTISTS.  ACTA PROTOZOOLOGICA 
33: 1-51.  ESSENTIALLY RETAINS MUCH TRADITIONALISM BECAUSE OF ITS 
CONVENIENCE 

PATTERSON, DJ 1994  PROTOZOAN EVOLUTION AND CLASSIFICATION.  PROGRESS IN 
PROTOZOOLOGY, PROC 10TH INT. CONG. PROTOZOOOL BERLIN. FISCHER VERLAG 
(ATTEMPTS PHYLOGENETIC - INCIDENTALLY THEY TELL ME THIS IS OUT BUT I 
HAVEN'T SEEN IT SO I CAN'T OFFER PAGES)

YOU COULD ALSO TRY MARGULIS' ET AL HANDBOOK OF PROTISTOLOGY BUT I DON'T 
THINK THIS HAS ANY LOGICAL BASIS.


> 1. Earlier this summer Andrew Roger, David Patterson, and Mark Siddall
> debated the meaning of monophyly, and the value of the term holophyly. 
> That got me thinking about phenetics and cladistics approaches to 
> classifying protists.  I'd like to provide the students with protistan 
> examples of how different approaches to systematics results in different 
> classification schemes.  In particular, I'd like to use a) some examples in 
> which the difference rests on whether or not one attempts to distinguish 
> between common ancestry and convergence for some trait or traits, and 
> b) some examples in which the difference rests on whether or not one 
> attempts to distinguish between derived and primitive ancestral traits.  Any 
> suggestions?
> 
> 2. One set of traits of obvious importance would be plastid presence, 
> type, etc.  That chloroplasts have been lost often seems clear. The 
> origin of chloroplasts is not so clear.  The current trend in the literature 
> seems to favor a 
> monophyletic origin of plastids from some cyanobacterial ancestor, with 
> secondary symbioses within eukaryotes (e.g., cryptomonads). Wolfe et al. 
> (Nature Vol. 367, p. 566, Feb. 10 1994) have evidence of 
> light-harvesing-complex proteins in red algal chloroplasts 
> (Porphyridium), and Larkeum et al. (PNAS Vol. 91, 679-683, Jan. 1994) 
> have evidence of chlorophyll c-like pigment (along with chlorophylls a and 
> b) in Prochloron.  So, is it reasonable to speculate that the photosynthetic 
> prokaryote that became the first chloroplast could have had phycobilisomes, 
> antenna complex proteins,  and all three chlorophylls? Or, is it more 
> likely that the use of certain chlorophylls evolved multiple 
> times independently?  Finally, how about the idea of a polyphyletic 
> origin for chloroplasts, a la Dodge?  Is that still viable?

I DON'T THINK THIS ONE HAS BEEN PUT TO BED YET
> 
> 3. F.J.R. Taylor and others have placed great emphasis on the morphology of 
> mitochondrial cristae, but somewhere I read that mitochondrial cristae might
> assume a variety of shapes depending upon the physiological state of the 
> cell at the time of fixation, as well as the method of fixation.  What 
> seems to be the current majority opinion on the value of mitochondrial 
> cristae as a characteristic for systematics?

ALL EUGLENIDS HAVE THE SAME APPEARANCE OF CRISTAE, ALL CILIATES HAVE THE 
SAME BUT DIFFERENT ETC.  WITH CAUTION IT CAN BE USED AS A CHARACTER.  IT 
HAS BEEN DISCUSSED IN SOME OF THE LITERATURE - MOSTLY ON USING IT WITH 
FREE-LIVING FLAGELLATES
> 
D. J. PATTERSON



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