We’ve already had lots of discussion about Nicholson et al.’s (2012) recent proposal that Anolis be fragmented into eight genera. Throughout the course of this discussion, several posts and comments have suggested that anole biologists might be compelled to implement Nicholson et al.’s proposed generic revision by the International Committee on Zoological Nomenclature (ICZN) and its rules for nomenclature (a.k.a. the ICZN* or The Code) (see comments on recent posts by Losos and Sanger).
Although I must admit at the outset that I am not an authority on The Code or its implementation, I will argue below that the belief that the code compels anole biologists to accept Nicholson et al.’s proposed taxonomic revision is completely false. The ICZN has neither the authority, nor the interest in, policing taxonomic practice and will have no role in determining whether Nicholson et al.’s (2012) new generic classification is accepted or rejected by the community of researchers who study anoles. I believe that the reasons for this are fairly straightforward and uncontroversial, but they do require us to think a little about our taxonomic philosophy and the difference between taxonomy and nomenclature.
Let’s start with some basics for the non-systematists. According to the ICZN, the goal of taxonomy is “the identification and interpretation of natural groups of organisms (i.e., taxa) based on characters (such as morphology, genetics, behaviour, ecology).” One piece of good news for anole biology is that everyone involved in debate over Nicholson et al.’s new classification shares the same fundamental taxonomic philosophy – namely, that taxa should be diagnosed using phylogenetic trees and should correspond with monophyletic groups. We may debate whether certain taxa are supported as monophyletic by the available data, but we all agree that recognition of monophyletic groups is a primary objective of any taxonomic scheme for anoles.
More good news: The Code has no interest in getting involved with taxonomic decisions. I realize that the The Code can be really boring to read, but you don’t have to read more than the first two paragraphs of the introduction to get this message (in a few cases I’ve added my own emphasis by bolding text):
“The 4th edition of the International Code of Zoological Nomenclature … has one fundamental aim, which is to provide the maximum universality and continuity in the scientific names of animals compatible with the freedom of scientists to classify animals according to taxonomic judgments. The Code consists of Articles … [that] are designed to enable zoologists to arrive at names for taxa that are correct under particular taxonomic circumstances. The use of the Code enables a zoologist to determine the valid name for a taxon to which an animal belongs … There are certain underlying principles upon which the Code is based. These are as follows: (1) The Code refrains from infringing upon taxonomic judgment, which must not be made subject to regulation or restraint…”
Rather than concerning itself with taxonomy, which inevitably involves subjective decisions made by systematists that specialize on particular groups of organisms, The Code focuses exclusively on nomenclature, or “the system of scientific names for taxa (such as species, genera, or families) and the rules and conventions for the formation, treatment, and use of those names.” The Code, therefore, merely provides “a set of rules for the naming of taxa that follows an internationally agreed, quasi-legal procedure.”
With this background, we can return to a consideration of Nicholson et al.’s classification and the role that The Code may have in its implementation. Nicholson et al. argue that in order to appreciate and study the phylogenetic diversity of anoles we must formally recognize the taxon that includes all anoles not as a single genus, but rather as a number of related genera. Although determining whether to proceed with the traditional classification involving a single genus or the Nicholson et al. classification that recognizes eight genera might seem to be a distinction between two alternative systems of nomenclature whose outcome is dictated by the The Code, this is not the case. Instead, both alternatives are perfectly compatible with The Code, and the decision about which classification to adopt moving forward is a subjective taxonomic decision that must be made by the community of biologists who study anoles.
All The Code says is that if we anole biologists want to recognize the taxa that Nicholson et al. have diagnosed as genera, we must use the names they have resurrected from the historical literature and applied to these taxa. If I wrote a paper tomorrow that gave a new generic epithet to the same taxon that Nicholson et al. have named Ctenonotus, this new name would be rejected under the rules of priority outlined in The Code. However, The Code respects the right of anole biologists to make the subjective taxonomic decision about whether we want to recognize the taxa diagnosed by Nicholson et al. as genera, or instead recognized them informally as series or species groups, as anole biologists have done for decades. Recall from our earlier passage from The Code that its rules for nomenclature only apply “under particular taxonomic circumstances.”
My fellow anole biologists, we have a taxonomic decision to make and the ICZN is not going to make it for us. It seems that the worst outcome would be fragmentation of the community of anole biologists, with some researchers using the traditional approach and others applying Nicholson et al.’s revised generic classification. More readings and notes are after the fold.
For those who are interested in learning more about the taxonomic issues raised in this post, I encourage you to check out a few other recent papers on this issue:
de Queiroz, K., and M. J. Donoghue. 2011. Phylogenetic nomenclature, three-taxon statements, and unnecessary name changes. Systematic Biology 60:887-892 [doi link].
Pauly, G. B., D. M. Hillis, and D. C. Cannatella. 2009. Taxonomic freedom and the role of official lists of species names. Herpetologica 65:115–128 [doi link].
Hillis, D. M. 2007. Constraints in naming parts of the Tree of Life. Molecular Phylogenetics and Evolution 42:331-338 [doi link].
* Yes, an organization whose only goal is to encourage clarity in the application of names uses the same acronym for two different things; ICZN stands for both the organization known as the International Commission on Zoological Nomenclature and the set of rules known as the International Code of Zoological Nomenclature.