[Taxacom] save Prokaryota!!! (was: Knocking Hennig off his pedestal

Ken Kinman kinman at hotmail.com
Sun Jan 26 19:44:07 CST 2014
















Hi Patrick,                                                                    Seems to me what is most important here is to emphasize that paraphyletic taxa are based on homologous character states as well (not those which are homoplastic/convergent. which we agree make polyphyletic taxa unnatural).  Furthermore, classifications which include paraphyletic taxa are more informative because they include both plesiomorphic and apomorphic character information (not just apomorphic, which thus renders "cladifications" less informative, less useful, and often less stable).  
       "Cladifications" are also often very asymmetric and thus unbalanced (which can add to instability), making them even harder to remember (and often harder for the general user to even understand).  This has resulted in an explosion of new clade names (many of which eventually turn out to be invalid) as well as a proliferation of categories that is so extreme that calls for the elimination of Linnaean categories naturally followed (but one shouldn't abuse a useful tool like that and then complain when problems arise). 
       And it seems to me that Prokaryota (a paraphyletic group of species) is just as valid and important as Eukaryota (a holophyletic group of species).  Add the two together and you get all cellular life on Earth.  The symplesiomorphies shared by Prokaryota and Eukaryota are extremely important, while a cladification of cellular life is unfortunately overly fixated on just a single synapomorphic character state for Eukaryota (possession of a nucleus).  In fact, cladifications are often regarded as just one character classifications (and that is definitely not a good thing to rely on).  
     And FINALLY, and to my mind MOST IMPORTANTLY, we can all actually in an important way "have our cake and eat it too", by simply adding my {{place-markers}} within a paraphyletic "mother" group showing the cladistic placement of the removed "daughter" exgroup.  For example, you simply place a {{Eukaryota}} place-marker within the Prokaryota classification showing its relationship to Archaebacteria.  That alone would invalidate many of the excuses that are made for not using paraphyletic taxa and bashing them as being bad (which is only true for the really BAD paraphyletic taxa, not for ALL paraphyletic taxa).  Again I implore strict cladists, don't throw the baby out with the bath water!!!
        ----------------Ken Kinman   
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> Date: Sat, 25 Jan 2014 22:51:08 -0700
> From: paalexan at polyploid.net
> To: taxacom at mailman.nhm.ku.edu
> Subject: Re: [Taxacom] Knocking Hennig off his pedestal
> 
> Or, phrased in a manner that seems more straightforward to me:
> 
> Polyphyletic groups are based on homoplastic character states. Both 
> monophyletic and paraphyletic groups are based homologous character 
> states. For monophyletic groups the homologous character states are 
> apomorphic, while for paraphyletic groups they are plesiomorphic.
> 
> However, this is just shoehorning phylogenetic terms into typology. It 
> assumes that you start with an ahistorical, similarity-based 
> classification and then examine how that classification maps onto 
> descent. A grouping of species is, on its own, only monophyletic or not. 
> Paraphyly and polyphyly are not characteristics of groups of species, 
> they are characteristics of a typological classification of those 
> species. They are only distinguishable if you accept a priori that 
> typology is the appropriate approach to defining groups of 
> species--which, of course, is diametrically opposed to the goals and 
> concepts of phylogenetic classification, which defines groups of species 
> by descent. From the viewpoint of phylogenetic classification, they are 
> equally bad because they are indistinguishable.
> 
> Patrick
> 






 		 	   		  


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