Systematics Pattern and
Transformed cladistics

Cladistics: Pattern and Transformed cladistics

Phylogeny and Systematics
   History of systematics
      The Great Chain of Being
      Linnaean taxonomy
      The Tree of Life
      Evolutionary systematics
      Molecular phylogeny
      Stratigraphy and phylogeny

   Cladistics - An Introduction
      Definition: Cladogram
      Definition: Monophyly
      Definition: Paraphyly
      Definition: Polyphyly
   Phylogenetic Systematics
   Pattern cladistics
   Cladistics and Paleontology
   Computational cladistics

In the late 70s and early 80s a new school of cladistics, called Pattern cladism was developed by Gareth Nelson and Nelson Platnick ("New York Cladists") in 1979, and later developed as Transformed cladism in the works of Colin Patterson (1982). Essentially a reaction to Ernst Mayr's evolutionary systematics, Pattern or Transform Cladism aims at the calculation of most parsimonious cladograms using the pattern of their characters alone, without any recourse to actual phylogeny, through separation of "pattern and process".

Pattern cladistics resembles phenetics in that it does not use character rooting and synapomorphies are not used, although monophyletic groups are acknowledged.

Ebach et al 2008 relate Transformed cladism to the works of Colin Patterson (1982) and Platnick (1979) and say that in contrast to pattern cladists who are Non-Hennigian, Transformed cladists are Hennigian and root their trees according to either outgroups, ontogeny or concepts such as set theory.... They opt for a definition of monophyly that does not include the most recent ancestor. They do not reject totally transformation, but they do use a concept of character rooting that is inherent within set theory". It seems however that these differences are mostly minor and the two are more usually synonymised.

Like phenetics, pattern and transformed cladists strove to be as objective and empirical as possible. They assert that a cladogram was merely a summary of shared characters, that could at best test a historical reconstruction (The philosophy of classification Pattern cladism and the myth of theory dependence of observation - John Wilkins) (as phylogenetic hypotheses), but reject the possibility that a real evolutionary history can ever be arrived at. There also tends to be a lack of interest in the fossil record, as fossils were considered to have insufficient characters to be used in a cladogram. Patterson's revision of the British Museum public displays caused something of a stir at the time, being greeted enthusiastically by Creationists who, totally failing to understand the purely pragmatic approach, thought that Darwinists had finally accepted there was no such thing as evolution.

Even so, the idea that science can be theory-neutral is itself philosophically problematic (Pearson 2010). Criticised by Richard Dawkins' The Blind Watchmaker, (quotes and comments here, but see this defense of pattern and transform cladism. (MAK, IAB blog)

Pattern cladism did not last long as a distinct movement, although its pragmatic empirical insights, such as cladistics as hypothesis testing (especially important in computational cladistics, where it is often necessary to choose between hundreds of possible cladograms), have been assimilated into Phylogenetic Systematics, the two together simply being known as Cladistics. MAK130321

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