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Cladistic Analysis Or Cladistic Classification?": a Reply to Ernst Mayr

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Cladistic Analysis Or Cladistic Classification? "Cladistic Analysis or Cladistic Classification?": A Reply to Ernst Mayr Willi Hennig Systematic Zoology, Vol. 24, No. 2. (Jun., 1975), pp. 244-256. Stable URL: http://links.jstor.org/sici?sici=0039-7989%28197506%2924%3A2%3C244%3A%22AOCCA%3E2.0.CO%3B2-3 Systematic Zoology is currently published by Society of Systematic Biologists. Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/about/terms.html. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://www.jstor.org/journals/ssbiol.html. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is an independent not-for-profit organization dedicated to and preserving a digital archive of scholarly journals. For more information regarding JSTOR, please contact [email protected]. http://www.jstor.org Sun Apr 15 18:23:03 2007 POINTS OF VIEW 245 entific theory with that of a schedule, or question of what animal system is the format, of taxonomic activity. I doubt, best, I don't believe that it can be posed therefore, if Mayr's "evolutionary system- so generally (as Giinther has pointed out, atics" is really based on scientific theory- "the system of cook books is the best for a doubt that has been expressed often, the purpose of a cook book). For the perhaps most clearly by Johnson (1970), scientifically best system, Mayr, neverthe- who is himself an advocate of "evolutionary less, states several criteria, among which the systematics." best "explanatory, predictive, and heuristic Mayr's epistemological imprecision stands properties7' (p. 94) and an "efficient in- out clearly in his desire to build his "evolu- formation storage and retrieval system7' (p. tionary" system in a "synthetic7' (p. 95) 94) may be the most important. But I manner according to two different view- raise a question about the significance of points: phylogenetic and, also, adaptioge- the concept of "prediction," which seems to netic ( ecofunctional) . With this system, me a purely formal and meaningless meta- built according to two different viewpoints, phor, adopted by Mayr from a special group a user can never know of a particular group of biological theories to which no theory (taxon) if it is based and defined phy- of biological systematics belongs. Indeed, logenetically or adaptiogenetically (eco- the concept of predictions plays no further functionally). This circumstance, contrary role in Mayr's presentation-except to fig- to Mayr's belief, reduces the information ure in some very general assertions ("The content of his "evolutionary" system (see number of evolutionary statements and below). predictions that can be made for many The logical demand for strict uniformity holophyletic groups . [that is, the mono- of viewpoint in the arrangement of systems phyletic groups of phylogenetic system- (already established although not always atics] is often quite minimal" [p. 961). followed by Aristotle), is neither mentioned And it seems to me that Mayr, contrary nor refuted by Mayr. He would, perhaps, to his stated purpose, agrees with my reject this demand as formalistic, for he opinion of the logical priority of the phylo- elsewhere rejects other logical demands. genetic system: "The synthetic or evolu- But rejecting a logical demand is not in tionary method of classification . agrees itself a valid scientific refutation, and is with cladistics in the postulate that as com- at best a reckless practice--even outside plete as possible a reconstruction of phy- the sciences. logeny must precede the construction of a classification" (p. 95) and "Hennig is quite right when he states: 'phylogenetic re- I will now consider the particular ob- search as biological science is possible only jections enumerated above, with which if it adopts the discovery of the genealogical Mayr contests the scientific permissibility relation of species as its first objective' " (p. of phylogenetic systematics. 97). "The cladists are sincerely convinced that Here I draw attention to a distinction their theory produces the best classifica- that might be made between the concept of tions" (p. 96). This assertion, with which system and that of classification. Let me Mayr introduces his refutation of this al- begin with an example. If an archaeologist leged claim of the "cladists," is false, as discovers potsherds in a tomb, he might is evident by examination of Mayr's cita- begin by ordering, or classifying, them in tion ( Hennig, 1971) : I have maintained some way: according to their material only that the phylogenetic system, as a (clay or metal), their color, their decora- general reference system, has a certain tions, etc. Subsequently, he might attempt logical priority; and this statement is not to reconstruct the original vessels (vases, the same as Mayr's assertion. As for the urns, etc.), of which the potsherds are SYSTEMATIC ZOOLOGY fragments. This reconstruction is another fute the "cladists." It is a type of argument kind of ordering. One might call it a that he uses also in other places in his paper. system, but one need not call it a classifica- In actuality, the conversion of a clado- tion. For another example, I refer to the gram into a hierarchical system is possible rivers of Europe. These may be classified without a single additional assumption or according to their navigability, water man- the redefinition of any of the concepts used agement, the conditions they offer for the in constructing the cladogram. The con- settling of organisms, etc. But one might version is a purely formal operation. Given seek to determine the drainage (Danube, the cladogram of Mayr's Fig. la, for ex- Rhine, Elbe, etc.) to which each belongs, ample, the following hierarchy results: in order to construct a different kind of system of rivers. Similarly, the construc- Taxon (B + C + D) tion of a cladogram in accordance with I. Taxon B the principles of phylogenetic systematics 11. Taxon (C + D) results in a system rather different in prin- 1. Taxon C ciple from various kinds of possible classifi- 2. Taxon D cations. Although my original perception Why I often prefer a hierarchical system of this distinction was somewhat unclear, to a cladogram also needs brief discussion I have nevertheless avoided speaking of (sections &7). phylogenetic "classification," preferring in- stead phylogenetic "system"-but I have 4. sometimes used "classification" under the influence of English usage. The logical priority of the phylogenetic A peculiar defect in Mayr's work, one system, as a general reference system, arises which jeopardizes the whole of what he from its foundation in a biological theory presents a fundamental contribution, is that with unambiguously defined central con- he disputes (p. 100) the conversion of a cepts. Mayr, however, objects to what cladogram into a hierarchical system: "As he terms "arbitrary decisions, involving a valuable as the cladistic analysis is, it does redefinition of well known terms" (p. 100) not automatically provide a classification" and I respond as follows: (p. 123), and "The basic postulate of the cladistic theory, a complete congruence of a. Phylogenesis, a term coined by Haeckel a cladogram and classification, can be satis- more than 100 years ago, has never before fied only by making numerous assumptions been unambiguously defined. The Greek and redefinitions and by ignoring numerous word roughly means origin of phyla (groups facts of evolution and phylogeny (broadly of common descent). According to evolu- defined)" (p. 100). tionary theory, phyla originate by succes- These assertions are simply false. They sive cleavage events within organismic would be correct if "classification sew communities of reproduction. Phylogenetic Mayr" were inserted in the two sentences systematics defines phylogenesis in this un- ambiguous sense. Mayr considers this in place of "classification." Then, neither definition erroneous, and adds, as a second Mayr nor I would dispute their truth. Mayr "set of factors" the "amount and nature of here confuses the aims of "cladists" with evolutionary change between branching those of "evolutionists" (with respect to points" (p. 95). But these companion phe- the construction of systems), although he nomena of phylogenesis, which vary more previously described correctly the differ- or less in different sister-groups, are dis- ences between the two. And he reproaches cussed in the literature under the terms the "cladists" because they proceed dif- adaptiogenesis and anagenesis (or aramor- ferently than he wishes. Through this re- phosis ), about which, however, there is markable solipsism, Mayr presumes to re- some ambiguity of meaning. Because he POINTS OF VIEW 247 senses, perhaps, that these are logically traditional definition, that a group is "mono- secondary epiphenomena of phylogenesis, phyletic" if its members have a common Mayr calls his recommended theory of sys- ancestor, is recognized by Mayr himself, tematics "evolutionary" rather than phylo- who adds the qualification that "the com- genetic. ponent species, owing to their characteris- tics, are believed to be each other's nearest b. Relationship is a term that in English as relatives" (p. 104). But the value of his well as German means either form rela- addition is annulled by the ambiguity of tionship or genealogical ( blood) relation- the term "nearest relatives." If one under- ship. Mayr defends this ambiguity even stands "nearest relatives" in the genealogi- for the practice of biological systematics, cal sense (rather than the form sense), thereby disregarding the need for unam- then the only difference between Mayr's biguously defined terms and precise con- definition and that of phylogenetic system- cepts.
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