Posted by:
CKing
at Fri Nov 14 09:41:03 2003 [ Email Message ] [ Show All Posts by CKing ]
Kurt Schwenk writes:
"Therefore, phylogeny reconstruction is not only an end in itself, but is the necessary starting point for many evolutionary questions. Seen in this light, any rigorous attempt to reconstruct phylogeny is laudable. Therefore, Lazell’s(1992:109) initial question of 'why--what good does it do' indicates a failure to appreciate the fundamental importance of Frost and Etheridge’s (1989) attempt to reconstruct the phylogeny of Iguania and that the fragmentation of the traditional family Iguanidae into several, less inclusive taxa follows directly from this attempt."
Does Kurt Schwenk represent Lazell's view accurately?
Here is what Lazell says:
"The first issue for me confronting a drastic taxonomic fragmentation of this sort is 'why'--in the sense of 'what good does it do?'"
Lazell is referring to the taxonomic fragmentation of Iguanidae by Frost and Etheridge when he asks the question "what good does it do?" Lazell is not questioning the need to reconstruct phylogeny.
Lazell continues:
"In any case, while Frost and Etheridge provide equivocal evidence for paraphyly in the previous arrangement of three iguanian families, they present no compelling proof. Indeed, they present no new factual evidence at all and provide no definitive phylogeny."
Frost and Etheridge's attempt to reconstruct phylogeny therefore fails. Their fragmentation of Iguanidae is therefore not based on a hypothesis of phylogeny, but based on characters that members of these "families" have in common with one another.
Lazell writes:
"Conversely, tropidurines (or 'Tropiduridae') and crotaphytines (or 'Crotaphytidae') share many aspects of gestalt: they are rather similar looking lizards. Frost and Etheridge separate them as distinct families on the basis of three characters: femoral pores, gular fold, and S-condition of the nasal chamber in crotaphytines."
Indeed, because Frost and Etheridge lack a "definitive phylogeny" and because they construct their taxa using a few characters, they are practicing what Mayr and Ashlock term "pre-Darwinian facile diagnosis."
Mayr and Ashlock write:
"Rebounding from the extreme of phenetics, the cladists unwittingly returned to the ideal of pre-Linnaean taxonomy: facile diagnosis. ...Many branching points in a cladogram are based on changes in a single character or at most a very few characters. For this reason cladistic classifications may have the vulnerability of any single-character classification. ...The validity of taxa based on a single character or a few characters is often refuted by further analysis."
Hence Lazell is not arguing whether phylogenetic reconstruction is any good, he is asking what good there is in the fragmentation of Iguanidae in the absence of both a definitive phylogeny and new evidence. If a proposed change is drastic and it is not based on a definitive phylogeny, then it obviously does not do any good, and it should be rejected. Of course, most people do not really care about taxonomy except that they should keep themselves current. Therefore they will accept any new proposed change if somebody else are using it. For those who know better, they know taxonomic stability is of utmost importance to scientific progress. For those who know better, taxonomic proposals that do not do any good, such as Frost and Etheridge's proposal, should indeed be rejected.
Reference
Lazell, J.D., Jr. 1992. The family Iguanidae: disagreement with Frost and Etheridge (1989). Herpetol. Rev. 23(4):109-112.
Mayr, E. and P. Ashlock 1991. Principles of Systematic Zoology, 2nd. ed.
Schwenk, Kurt 1994. Systematics and Subjectivity: The Phylogeny and Classification of Iguanian Lizards Revisited. Herpetol. Rev. 25(2):53-57
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RE: Iguanian Classification: "Fait Accompli" or Completely Undone? - CKing, Fri Nov 14 09:41:03 2003