Phylogenetic Systematics of Odonata


© Günter Bechly, Böblingen, 2005


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Phylogenetic Taxonomy and Synonymy



BASIC PRINCIPLES OF PHYLOGENETIC TAXONOMY (sensu Bechly):

  1. Only (hypothetical) time-biospecies and (sufficiently well supported) clades (monophyletic groups of biparental species) or clones (monophyletic groups of uniparental organisms) may be scientifically named. All taxa above the species-group level must be demonstrably monophyletic. Traditional taxa that are probably paraphyletic but can not yet be split into several monophyletic taxa, and metataxa that have neither been demonstrated to be monophyletic, nor paraphyletic, may be preliminarily included in a phylogenetic classification if and only if they are clearly indicated by quotation marks.
  2. All recognized fossil and extant species and monophyla must be scientifically named. Sequencing is rejected as principle of classification.
  3. The diagnosis of a new species must include at least one safe diagnostic character (preferably an autapomorphy) or a 100% diagnostic combination of characters, while the diagnosis of a new clade always must include at least one convincing autapomorphy. Preferably a list of all known important autapomorphies should be provided with the description of a new taxon.
  4. In the original description of a new species, the underlying species concept should be clearly specified.
  5. Each new description of a supraspecific taxon has to be provided with a recommened usage (list of included taxa).
    Contrary to previous statements of mine, I do not longer regard standardized phylogenetic definitions as necessary or useful, because such definitions do not guarantee the stable associating of a taxon name with a precisely specified clade, since this association is always highly depending on the underlying phylogenetic hypotheses. Consequently, phylogenetic definitions only provide stable names for unstable concepts and are rather ignorant to the content of the taxa (DOMINGUEZ & WHEELER, 1997).
  6. Names of monophyletic groups have to be regarded as synonyms if and only if they refer to exactly the same clade. Names originally proposed for polyphyletic and paraphyletic groups have to be regarded as synonyms of the least inclusive clade that contains the complete polyphylum or paraphylum as specified in the original description. If there is clear evidence in the original publication that the author intended to name a clade different from the least inclusive clade that includes all enumerated members, because the author did not know certain taxa (e.g. that were not yet described), forgot to mention certain taxa, or accidently or erroneously included or excluded certain taxa, the intention of the author is to be preferred. (Please note: This rule is in conflict with the current regulations of IRZN, which completely ignores the content of taxa and therefore allows names of different clades to be nomenclatural synonyms!)
  7. The first published name that was explicitly associated to a certain clade has priority and should become the only valid name for this clade, except when a well-established name would have to be replaced by a hardly known older synonym, or when this would imply a serious alteration of the traditional usage of the refering names, or if the use of the older synonym could cause considerable confusion. (Please note: This rule is in conflict with the current regulations of IRZN, which completely ignores the content of taxa and therefore allows names of different clades to be nomenclatural synonyms!)
  8. In case of homonymy the junior homonym has to be replaced by the oldest available synonym or a new name if no synonym is available. The replacement of the senior homonym may be preferred if and only if this would imply a significantly less serious alteration of the traditional usage of the refering names than the replacement of the junior homonym. (Please note: This rule might conflict with the current regulations of IRZN, since the latter does only consider homonymy within family-group, genus-group, and species-group taxa, but not between those groups!)
  9. Long established and well-known taxon names (e.g. Mammalia) should be preferably used for the referring crown-group (the least inclusive monophyletic group that includes all extant representatives). In case of a taxon name that refers to a certain character (e.g. Tetrapoda, Pinnipedia, Pterygota), the name should be used for the least inclusive monophyletic group that includes all species that posess this character by homology.
  10. Categorical ranks above the species-group level are rejected as biologically meaningless and arbitrary constructs, unless there will be established a new ranking system in which the categorical ranks are associated with a certain age of origin of the referring taxa. Likewise standardized prefixes or suffixes are generally rejected. Consequently, sistergroups do not have to have the same "rank" or suffix. The encaptic hierarchy of groups within groups is therefore indicated by corresponding indentions of the names in the written classification; sistergroups are indented on the same level. (Please note: This rule is in conflict with the current regulations of IRZN, which are strongly rooted in the obligatory usage of categorical ranks!)
  11. Taxa of uncertain phylogenetic position are indicated with the remark "incertae sedis", and taxa within an unresolved polytomy are indicated with the remark "sedis mutabilis".
  12. If a fossil stem-species can be identified as such, it has to be listed in parentheses on the same line and in front of the name of the taxon that originated from this stem-species. Hybrid-species (incl. cleptons) are listed twice in the classification, after their two parent species respectively (on the same line, separated by a semicolon).

REFERENCES:

ARCHIBALD, J.D. (1994): Metataxon concepts and assessing possible ancestry using Phylogenetic Systematics. Syst. Biol., 43(1): 27-40
AX, P. (1988): Systematik in der Biologie. Fischer: Stuttgart. 181 pp.
BRYANT, H.N. (1994): Comments on the phylogenetic definition of taxon names and conventions regarding the naming of crown clades. Syst. Biol., 43(1): 124-130
BRYANT, H.N. (1996): Explicitness, stability, and universality in the phylogenetic definition and usage of taxon names: A case study of the phylogenetic taxonomy of the Carnivora (Mammalia). Syst. Biol., 45(2): 174-189
CANTINO P.D. & OLMSTEAD R.G. & WAGSTAFF S.J. (1997): A comparison of phylogenetic nomenclature with the current system: A botanical case study. Syst. Biol., 46(2): 313-331
DE QUEIROZ, K. (1994): Replacement of an essentialistic perspective on taxonomic definitions as exemplified by the definition of "Mammalia". Syst. Biol., 43(4): 497-510
DE QUEIROZ, K. (1997): The Linnean hierarchy and the evolutionization of taxonomy, with emphasis on the problem of nomenclature. Aliso, 15 (in press)
DE QUEIROZ, K. & GAUTHIER, J. (1990): Phylogeny as a central principle in taxonomy: Phylogenetic definitions of taxon names. Syst. Zool., 39(4): 307-322
DE QUEIROZ, K. & GAUTHIER, J. (1992): Phylogenetic taxonomy. Annu. Rev. Ecol. Syst., 23: 449-480
DE QUEIROZ, K. & GAUTHIER, J. (1994): Toward a phylogenetic system of biological nomenclature. Trends Ecol. Evol., 9: 27-31
DOMINGUEZ, E. & WHEELER, Q.D. (1997): Taxonomic stability is ignorance. Cladistics, 13(4): 367-372
LUCAS, S.G. (1992): Extinction and the definition of the class Mammalia. Syst. Biol., 41(3): 370-371
ROWE, T. & GAUTHIER, J. (1992): Ancestry, paleontology, and definition of the name Mammalia. Syst. Biol., 41(3): 372-378
SCHANDER, C. & THOLLESSON, M. (1995): Phylogenetic taxonomy - Some comments. Zool. Scr., 24: 263-268
SUNDBERG, P. & PLEIJEL, E. (1994): Phylogenetic classification and the definition of taxon names. Zool. Scr., 23:, 19-25
WILLMANN, R. (1989): Paleontology and the systematization of natural taxa. pp. 267-291 in: SCHMIDT-KITTLER, N. & WILLMANN, R. (eds.) (1989): Phylogeny and the Classification of Fossil and Recent Organisms. - Abh. naturwiss. Ver. Hamburg, (NF) 28: 300 pp.
WYSS, A.R. & MENG, J. (1996): Application of Phylogenetic Taxonomy to poorly resolved crown clades: A stem-modified node-based definition of Rodentia. Syst. Biol., 45(4): 559-568



SYNONYMY:

There are two fundamentally different types of synonymy, which can either be involved separately, or in combination:

A general problem of the current International Rules of Zoological Nomenclature (IRZN) is the obligatory use of categorical ranks in combination with typified names (names based on a type species or type taxon), and the so-called Principle of Coordination (Art. 36 IRZN). This problem is most difficult above the species-group level, since the above mentioned principles imply the most unfortunate circumstance that the names of different taxa with very different taxonomic content may have to be regarded as nomenclatural synonyms. For example all taxa of family rank that include the type species Libellula quadrimaculata LINNAEUS, 1758 are synonyms of Libellulidae LEACH, 1815, although they could theoretically include any group of odonates from the complete pan-monophylum Odonatoptera to just the single type species. This is a quite unsatisfactory situation from the viewpoint of Phylogenetic Taxonomy, since only the content of the taxa is of biological interest, while it is actually completely irrelevant within traditional taxonomy. I therefore decided to include in my synonymy of the "higher" taxa of Odonatoptera the mere nomenclatural synonyms as well as the volumetrical synonyms. This goal of course requires an adequate terminology that unequivocally indicates the type of synonymy involved. This is achieved by the following provisions:

  1. The citation of a new taxonomic name is immediately followed by the author and publication year, except when it is listed as a volumetrical synonym. In the latter case there is a "sensu" between taxon name and author. After the citation of a new taxonomic name there may be a statement in parentheses about the originally proposed categorical rank of the new taxon (taxon nov., superfam. nov., fam. nov., subfam. nov., trib. nov., subtrib. nov., gen. nov., spec. nov.). Furthermore there may be an additional statement in parentheses about the nomenclatural status of the taxon (nom. imperf., obj. inv. name, obj. jun. syn., subj. jun. syn., homonym, etc.).
  2. In case of a subsequent citation, there is also a "sensu" between taxon-name and author in case of complete volumetrical synonymy, while there is only a "; " between taxon-name and author in case of mere nomenclatural synonymy. A subsequent citation may be followed by a statement in parentheses about the taxonomical change suggested by the referring author (stat. nov., stat. rest., sens. nov., nom. correct.).
  3. Available Taxa that are volumetrical synonyms, but not nomenclatural synonyms, are listed in square brackets "[...]". The latter case mostly occurs when a higher taxon or a genus-group taxon corresponds to a family-group taxon or vice versa.
  4. Nomina nuda and unpublished manuscript names (unavailable names) as well as junior homonyms, junior objective synonyms and totally suppressed names (objectively invalid names) are listed in braces "{...}".
  5. Polyphyletic and paraphyletic taxa are indicated by quotation marks and are listed in the synonymy of the closest monophyletic taxa in two different ways:
    a) They are listed as "partial" volumetrical synonyms in the synonymy of the least inclusive clade that includes the complete polyphylum or paraphylum:
    ... in the case of the original description they are indicated as ...: incl. "Taxon" AUTHOR date;
    ... in the case of a subsequent usage they are indicated as ...: incl. "Taxon"; AUTHOR date.
    b) They are listed as "partial" volumetrical synonyms in the synonymies of all those monophyla that together constitute the polyphyletic or paraphyletic group:
    ... in the case of the original description they are indicated as ...: partim "Taxon" AUTHOR date;
    ... in the case of a subsequent usage they are indicated as ...: partim "Taxon"; AUTHOR date.
  6. Monophyletic taxa that have been preliminarily synonymised with the next superordinated monophylum, because their recognition would result in a paraphyletic rest-group, are listed as mere nomenclatural synonyms in the synonymy of the superordinated monophylum:
    ... in the case of the original description they are indicated as ...: incl. Taxon AUTHOR date (jun. subj. syn.);
    ... in the case of a subsequent usage they are indicated as ...: incl. Taxon; AUTHOR date.
  7. The so-called "légions" of Selys-Longchamps are rejected, since they are clearly not available as family-group taxa according to Art. 11(f) IRZN. They can only be regarded as informal names (vernacular or trivial names).


TAXONOMIC TERMINOLOGY & ABBREVIATIONS:

A very good glossary of taxonomic terminology can be downloaded from the website of BIOSIS.

The terminology of Phylogenetic Systematics is thoroughly explained and discussed in my Glossary of Phylogenetic Systematics.




Last Update: 25th July, 2005

© Günter Bechly, Böblingen, 2005