PhyloCode
The International Code of Phylogenetic Nomenclature, known as the PhyloCode for short, is a developing draft for a formal set of rules governing phylogenetic nomenclature. Its current version is specifically designed to regulate the naming of clades, leaving the governance of species names up to the rank-based Nomenclature codes.
The PhyloCode is associated with the International Society for Phylogenetic Nomenclature. The companion volume, Phylonyms establishes 300 taxon names under PhyloCode, serving as examples for those unfamiliar with the code. RegNum is an associated online database for Phylogenic names.
The PhyloCode proposes to regulate phylogenetic nomenclature by providing rules for how to decide which associations of names and definitions will be considered established, which of those will be considered homonyms or synonyms, and which one of a set of synonyms or homonyms will be considered accepted. The PhyloCode will only allow the naming of clades, not of paraphyletic or polyphyletic groups, and will only allow the use of specimens, species, and apomorphies as specifiers.
Phylogenetic nomenclature
Unlike rank-based nomenclatural codes, the PhyloCode does not require the use of ranks, although it does optionally allow their use. The rank-based codes define taxa using a rank and, in many cases, a type specimen or type subtaxon. The exact content of a taxon, other than the type, is not specified by the rank-based codes.In contrast, under phylogenetic nomenclature, the content of taxa are delimited using a definition that is based on phylogeny and uses specifiers to indicate actual organisms. The formula of the definition indicates an ancestor. The defined taxon, then, is that ancestor and all of its descendants. Thus, the content of a phylogenetically defined taxon relies on a phylogenetic hypothesis.
The following are examples of types of phylogenetic definition :
- Node-based: "the clade originating with the most recent common ancestor of A and B" or "the least inclusive clade containing A and B"
- Branch-based: "the clade consisting of A and all organisms or species that share a more recent common ancestor with A than with Z" or "the most inclusive clade containing A but not Z." Another term for definitions of this sort is stem-based.
- Apomorphy-based: "the clade originating with the first organism or species to possess apomorphy M inherited by A".
The following table gives examples of phylogenetic definitions of clades that also have ranks in traditional nomenclature. When all the specifiers in a node-based definition are extant specimens or species, as in the following definition of Mammalia, a crown group is defined.
| Name | Rank | Type | Possible phylogenetic definition |
| Tyrannosauridae | Family | Tyrannosaurus Osborn 1905 | Least inclusive clade containing Tyrannosaurus rex Osborn 1905, Gorgosaurus libratus Lambe 1914, and Albertosaurus sarcophagus Osborn 1905 |
| Mammalia | Class | N/A | Clade originating with the most recent common ancestor of humans, Homo sapiens Linnaeus 1758, and platypuses, Ornithorhynchus anatinus Shaw 1799 |
| Rodentia | Order | N/A | Most inclusive clade containing the house mouse, Mus musculus Linnaeus 1758, but not the eastern cottontail, Sylvilagus floridanus Allen 1890 |
| Neornithes | Subclass | N/A | Clade originating with the most recent common ancestor of the extant members of the most inclusive clade containing the house sparrow Passer domesticus Linnaeus 1758 but not the dinosaur Stegosaurus armatus Marsh 1887 |
| Tetrapoda | Superclass | N/A | Clade originating with the earliest ancestor from which Homo sapiens Linnaeus 1758 inherited limbs with fingers or toes |
Versions
The draft of the PhyloCode has gone through several revisions. All older versions can be found ., the current version is 5, finalized January 2014 and released 21 January 2019.Organization
As with other nomenclatural codes, the rules of the PhyloCode are organized as articles, which in turn are organized as chapters. Each article may also contain notes, examples, and recommendations.Table of contents
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Registration database
As currently planned, however, the most important use of RegNum will be the decision of which one of a number of synonyms or homonyms will be considered accepted: the one with the lowest registration number, except in cases of conservation.
History
The PhyloCode grew out of a workshop at Harvard University in August 1998, where decisions were made about its scope and content. Many of the workshop participants, together with several other people who subsequently joined the project, served as an advisory group. In April 2000, a draft was made public on the web and comments were solicited from the scientific community.A second workshop was held at Yale University in July 2002, at which some modifications were made in the rules and recommendations of the PhyloCode. Other revisions have been made from time to time as well.
The First International Phylogenetic Nomenclature Meeting, which took place from July 6, 2004 to July 9, 2004 in Paris, France, was attended by about 70 systematic and evolutionary biologists from 11 nations. This was the first open, multi-day conference that focused entirely on phylogenetic nomenclature, and it provided the venue for the inauguration of a new association, the International Society for Phylogenetic Nomenclature. The ISPN membership elects the Committee on Phylogenetic Nomenclature, which has taken over the role of the advisory group that oversaw the earlier stages of development of the PhyloCode.
The Second International Phylogenetic Nomenclature Meeting took place from June 28, 2006 to July 2, 2006 at Yale University.
The Third International Phylogenetic Nomenclature Meeting took place from July 21, 2008 to July 22, 2008 at Dalhousie University.
Influences
The theoretical foundation of the PhyloCode was developed in a series of papers by de Queiroz and Gauthier, which was foreshadowed by earlier suggestions that a taxon name could be defined by reference to a part of a phylogenetic tree.Whenever possible, the writers of the PhyloCode used the draft BioCode, which attempted to unify the rank-based approach into a single code, as a model. Thus, the organization of the PhyloCode, some of its terminology, and the wording of certain rules are derived from the BioCode. Other rules are derived from one or more of the rank-based codes, particularly the botanical and zoological codes. However, many rules in the PhyloCode have no counterpart in any code based on taxonomic ranks because of fundamental differences in the definitional foundations of the alternative systems.
Future
The PhyloCode is controversial and has inspired considerable criticism from some taxonomists.While inaugurated decades ago, the number of supporters for widespread adoption of the PhyloCode is still small. While Phylonyms were published in spring 2020, it remains unclear how the code will be implemented and how widely it will be followed. Some supporters believe that it should only be implemented, at least at first, as a set of rules accompanying the associated registration database, , and that acceptance by the scientific community may proceed from the popularization of RegNum as a utility for finding clade names and definitions.
A list of published critiques of the PhyloCode can be found on the , as can a list of rebuttals.
Literature
- including proposal, but without the 150 supporting signatories