Richard Wells wrote:
"Prayer, blind faith and slavish idolatry would be major prerequisites for a cladistic approach to taxonomy, so creationists would be preadapted to the method."

Me:
I think you have a good observation of the behaviors of some cladists, because--as P.C.H. Pritchard pointed out--sometimes cladism does take on the overtones of religious dogma and that some cladistic texts read more like the Koran than a scientific writing. Many cladists' adherence to Hennig's principle of holophyly (which states that a taxon must consist of one ancestor and all of its descendants) and Hennig's suggestion that only branching order should be taken into account when ranking organisms can only be described as being slavish.

That said, the cladists' approach to taxonomy is not really in any way similar to the creationists'. After all, ever since Charles Darwin, biologists have adhered to Darwin's suggestion that "the arrangement of the groups within each class, in due subordination and relation to other groups, must be strictly genealogical in order to be natural." The classifications of the Darwinians and cladists, and of course those of the pheneticists as well, are based on the idea (though not often realized in practice because of a lack of knowledge) that each taxon must share a common ancestor in order to be scientifically acceptable. Known unnatural polyphyletic groups that are based on convergent similarities are routinely rejected by all schools of biological classification.

If taxonomists of all schools reject polyphyletic groups, then what is the real difference between the various schools? For a detailed description of the many differences between the evolutionary systematists and the cladists, please refer to chapter 10 of Mayr and Ashlock's excellent book "Principles of Systematic Zoology, 2nd ed." The main difference between the cladists and all other schools of taxonomy is that cladist are unique in their adherence to Hennig's principle of holophyly. Cladists reject taxa that do not include some but not all descendant groups of a common ancestor. For example, referring to WW et al.'s paper, WW et al. would not recognize "Pailsus pailsei" because if the genus "Pailsus" is recognized, then Pseudechis becomes "paraphyletic," the same way that Reptilia is paraphyletic because two of the descendant groups of the common ancestor of Reptilia, namely birds and mammals, are excluded from Reptilia and classified in 2 other separate taxa, Aves and Mammalia. WW et al.'s rejection of "Pailsus" therefore has nothing to do with whether "Pailsus" is morphologically divergent from Pseudechis or not. To give an extreme example, even if "Pailsus" were to evolve a shell and a beak (thus making these snakes look more like turtles than snakes), the principle of holophyly would still forbid the cladists from recognizing it as a separate genus.

There is however, one way that a shelled and beaked "Pailsus" can be recognized that would nevertheless be acceptable to the cladists. That alternative would be to splinter the paraphyletic genus Pseudechis into many different but morphologically indefinable and indistinguishable genera. That means P. porphyriacus and P. guttatus would need to be classified in two different genera in order for "Pailsus" to be recognized, according to cladistic dogma. This second approach, while cladistically correct, is nonsensical since it substitutes one set of problems (way too many genera that are morphologically indistinguishable from one another) for another problem (a single morphological disparate genus). It is this second approach that Utiger et al. took to splinter the paraphyletic genus Elaphe.

Hopefully it is clear why evolutionary taxonomists have so stronly objected to many of the cladists' radical reclassification of familiar taxa. Fortunately, there is hope. As Ernst Mayr pointed out, "There is nothing in any theory of classification that would require one to rely on principle of holophyly." Indeed, even systematists who are not cladists can rely on Hennig's principle when classifying taxa. Hedges, for example, relied on Hennig's principle of holophyly when he reclassified Hyla regilla as "Pseudacris regilla," even though the type of data (distance data) he used is routinely rejected by cladists on philosophical grounds.

Cladistic analysis, therefore, is not to blame for much of the taxonomic chaos being generated, because after all, a phylogenetic analysis is little more than a hypothesis of phylogeny. It is most cladists' slavish reliance on Hennig's untenable principle of holophyly which is the main source of taxonomic chaos being generated.

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