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RE: Polyphyletic or Paraphyletic?

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Posted by: CKing at Sun Oct 5 14:13:24 2008  [ Report Abuse ] [ Email Message ] [ Show All Posts by CKing ]  
   

>>>>Bottom line: is phylogeny the pursuit of groups defined by relatedness or perceived similarity?
>>
>>Phylogeny is absolutely the pursuit of groups defined by relatedness (i.e. monophyly, not paraphyly or polyphyly).>>

Phylogeny is not the pursuit of grouping organisms. Phylogeny is the pursuit of determining evolutionary history. Grouping organisms on the basis of similarity is the pursuit of the taxonomist. Ever since Darwin, however, only those groups (which are delimited on the basis of similarity) that are demonstrably monophyletic (i.e. a group that share a recent common ancestor) are recognized. Groups that are found to be polyphyletic have been removed from the taxonomy ever since Darwin.

Phylogenetics is a separate branch of science than classification, which is itself not actually science. There are many biochemical phylogeneticists who are only interested in determining phylogeny but they are either not interested or not qualified to be taxonomists. They may publish a paper on phylogeny but they may not make any taxonomic proposals. Of course there are people who are interested in both phylogeny and classification as well, but phylogeny is not the same as classification.

>>Phenetics (a dead science) is based on similarity with no regard for relatedness. >>

Absolutely not! Pheneticists argue that evolutionary history is unknowable. Therefore the best way (to them) to find groups that are closely related to each other is to use overall similarity. Their reasoning was that if a group of organisms share a large number of similarities, then that group is likely to be closely related evolutionarily. Curiously, some cladists are making the same argument, yet they claim they are not pheneticists.

Of course, since convergence, reversal and parallelism are rampant, the pheneticist approach is demonstrably false. 2 organisms (such as the wolf and the thylacine (or marsupial wolf) can be remarkably similar because of convergence upon a similar lifestyle. In fact, many cladists are unwittingly practicing phenetics when they lump a group of organisms together on the basis of superficial similarities without critically analyzing the goodness of their taxonomic characters. A. Feduccia of the Univ. of North Carolina calls such practice "clado-phenetics."

So while few systematists call themselves pheneticists nowadays, many of them still carry on the practice, albeit unwittingly. Nevertheless the methods developed by pheneticists can be useful when determining disparity. And many of the procedures pheneticsts followed have now been adopted by the cladists. Sometimes one wonders whether some pheneticists merely morphed themselves into cladists in their never-ending assault on Darwinian taxonomy.

>>Frankly this is a silly debate. If you want to understand this stuff, read the literature. I entered this discussion to direction some to that literature, not debate an issue that is essentially dead.
>>
>>Cheers folks!

It appears that misunderstanding of phylogeny, systematic methodology and classification is rampant.


   

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<< Previous Message:  RE: Polyphyletic or Paraphyletic? - emoneill, Thu Oct 2 21:50:12 2008