We’ve had a lot of great discussion about Nicholson’s et al.’s proposal to split Anolis into eight genera. To date, most of the commenters have been against the proposal; I’d like to explain why I agree with this majority view.
Anole Annals summarized the arguments for splitting Anolis several days ago. Nicholson et al. argue that the failure to divide Anolis in the past has inhibited evolutionary and systematic research:
“Systematic progress in this regard has been delayed by an extremely conservative taxonomic approach to recognizing the diversity within the group and its extraordinarily ancient historical roots.” (p.4)
“The current practice (following Poe, 2004) of treating all dactyloids as comprising a single genus underemphasizes the evolutionary diversity within the family (as currently recognized) and obfuscates major biological differences among clades. In addition, simply because of the large size of the family (nearly 400 valid species), the single genus concept can be a hindrance to scientific communication regarding evolutionary events and directions of future research.” (p.13)
These quotes suggest that research on anoles is being held back by treating the entire clade as a single genus, but where is the evidence for these claims? No examples are provided. Quite the contrary, research on anoles has flourished over the last several decades, making it a well-known group for the study of many diverse evolutionary phenomena, and much of this work has explicitly incorporated phylogenetic information. Indeed, anole evolution, considered in a phylogenetic context, has become a commonly cited textbook example of adaptive radiation, and work on anoles has become so broad and deep that one commenter at last year’s Evolution meetings noted that “I didn’t go to the Evolution meetings for three years…When I “returned” in 2011 in Norman, it was like everybody had switched to working on anoles and sticklebacks!” The Dobzhansky Prize winners at the last two Evolution meetings have conducted phylogenetically-based research on anoles, and anole workers have nabbed the Fisher Prize and four Young Investigators Prizes at the meetings in that time span. Anole research is going gang-busters, and it is hard to see how retaining the name Anolis for the entire clade has had any sort of detrimental effect. (see also comments by Eric Schaad on why taxonomic names are no longer important for conducting phylogenetically-based evolutionary studies and by Yoel Stuart on why splitting evolutionarily-interesting clades may actually impede research).
I disagree with the proposal to split Anolis into eight genera for two reasons. First, it is not possible for the Linnean classification system to fully represent phylogenetic relationships—splitting genera simply changes the information conveyed, gaining some bits of information and losing others (for more discussion on this point, see the recent post by Luke Mahler and ensuing commentary). Second, splitting Anolis will be extremely disruptive for scientific researchers and the public.
1. It is not possible for the Linnean classification system to fully represent phylogenetic relationships
1. In the last three decades, the idea that our classification must reflect phylogenetic relationships has been widely accepted. As a result, all taxa must be monophyletic, and it is for this reason that the anole community has banished the genera Chamaelinorops, Chamaeleolis, and Phenacosaurus, placing the species within Anolis.
The problem is that with a clade of 400 species, there are 399 branching points (assuming a fully dichotomous tree). Given that the Linnean classification system has a limited number of ranks, there is no way that such a classification system can reflect the entirety of this phylogeny. Consider the Nicholson et al. phylogeny: by recognizing eight anole genera, it highlights the monophyly of these clades, something that is not apparent if one only recognizes Anolis. On the other hand, this classification does not reflect relationships among these clades (e.g., Audantia and Norops sister taxa, at least in their Fig. 5). Nor does it reflect relationships within those clades–the authors recognize that six of their genera are in turn composed of 20 subclades, but their generic level classification does not convey this information. Following the philosophy of Nicholson et al., one might expect that some day these clades will be raised to generic status, but doing so would lose the information on the fact that some of these clades are nested within others (e.g., if punctata and latifrons species groups, now within Dactyloa, become genera, then the classification will not reflect the fact that are both more closely related to each other than to clades outside of Dactyloa).
The bottom line is that there is no right or wrong. The Linnean classification system cannot portray all evolutionary relationships, and any particular system will highlight some and obscure others. Just because you can divide a genus doesn’t mean you should!
What are the alternatives? One is to use informal ranks to add information, such as the “species groups” and “species series” advanced by Williams and used by many. Another, suggested by David Hillis and others, is to use subgenera—in this case, the eight clades advanced by Nicholson et al. could be recognized as subgenera. Of course, this doesn’t solve all the problems—many evolutionary relationships remain unrecognized—but if these are the clades that are particularly important to recognize, then making them subgenera would do the trick.
Of course, there is a more radical solution. Some have proposed getting rid of the Linnean system entirely and replacing it with a rank-free, nested hierarchy of taxa. One way of implementing this proposal would be to employ Phylocode, a suggestion that is progressing slowly, but the discussions here make clear why such a system—at least in theory—would be useful. Perhaps we can convince a Phylocode proponent to post an explanation of how such a system would work with anoles, but just to give one example (if I have this correct), the species that is now recognized as Anolis frenatus might be known as Anolis/Dactyloa/latifrons Series/frenatus corresponding to the species latifrons falling within the larger latifrons Series clade, which is in turn within the Dactyloa clade, within the Anolis clade. Of course, the number of clades to specify and recognize with names would be up to the individual, and this species still could referred to as Anolis frenatus or Anolis/Dactyloa/frenatus or any other combination. In any case, I conclude that if we truly want our classification system to reflect all evolutionary relationships, something like this is the only way to do it.
2. Splitting Anolis will be extremely disruptive
Many of the previous commenters and posters have commented on the detrimental effects of splitting up a genus the name of which is so well entrenched in the literature. Before I address this point, I’d like to make an observation: some day, everything may be so seamlessly integrated that when a taxonomic revision occurs, all previous uses of the old taxonomy will be updated. When we look up old articles online, there will be a little link or yellow bubble notifying the reader that what used to be called Anolis conspersus is now Norops conspersus. Databases will be automatically adjusted, and all references online will be corrected. When that day comes, these issues will be moot. Unfortunately, that day is probably a long way off.
In the here and now, splitting Anolis will be incredibly disruptive. Previous commenters have noted the difficulties with keeping names straight on databases, with reorganizing museum collections, and so on. What is important to realize is that many of the users of systematics are not accustomed to dealing with situations such as this. Systematists and evolutionary biologists may realize that they have to be aware that names change through time, but most people have no clue. As Thom Sanger pointed out, anoles are now widely studied in many biological fields outside of evolution; even more importantly, anoles are now used in many activities far beyond academia. These people will not only be confused by the change of names, but they will not be adept at reconciling the enormous body of research conducted under the name “Anolis” with the new names.
I’d like to list some of the specific problems that these name changes will entail:
1. As Luke Mahler noted, for the last century, the name “Anolis” has applied to all 400 species in the clade. However, Nicholson et al. would restrict that name to a clade of 43 species, now commonly referred to as the “carolinensis Series.” One can easily see how a worker reading the pre-2012 literature might mistakenly think that an attribute of the entire 400-species clade applies to the much smaller clade that would bear this name. Indeed, an analogous example was just discussed in AA: a recent paper on species richness included as a data point the clade now known as “Iguanidae” which contains only iguanas (about 35-40 species), but attributed to that clade the species richness of the much larger clade that used to be called “Iguanidae,” which includes not only iguanas, but also many other types of lizards and contains perhaps 30 times more species than the new conception of Iguanidae (in other words, it suggested that there were 1000 or so species of iguanas). It is easy to see how naïve readers would be confused about the old and new uses of “Anolis.”
2. The opposite problem will exist as well. Throughout most of the history of anole research, the name “Chamaelinorops” has been attached to a single species, the enigmatic Hispaniolan species known until recently as Chamaelinorops barbouri and now called A. barbouri. However, Nicholson et al. have resurrected the name Chamaelinorops for a clade now containing nine species. Anolis barbouri has some very unusual morphological and behavioral characteristics, and it is easy to see how researchers in the future might be misled by reading the old literature into incorrectly thinking that those attributes apply to all nine members in the newly reconstituted Chamaelinorops.
3. Changes in species names made by Nicholson et al.: many people are unaware that generic and specific names have genders (as do words in Romance languages). According to the rules of zoological nomenclature, there are complicated rules, which I do not fully understand, about gender matching of generic and species names, which means that if a species formerly in a masculine genus (such as Anolis) is placed into a feminine genus (such as Deiroptyx, Dactyloa, and Audantia), then the species names must be changed (or something like this–maybe an authority on these issues can provide the exact rationale). Regardless of the exact rule, the result in this case is clear, a substantial number of anole species will have their names changed. For example, Anolis occultus will become Deiroptyx occulta and A. aeneus will become Dactyloa aenea. Some of the name-changing species are those with a long history in the literature; it is easy to see how an ecologist, for example, would have no clue that all of the work in the past on A. aeneus pertained to D. aenea. Indeed, I think most non-systematists are unaware that species names change in this way, and would not even consider that aeneus and aenea refer to the same species, especially when they have different generic names.
4. Multiple anoles with the same name: Now we’re getting very obscure. It turns out that two anole species were described in different genera, but with the same last name, darlingtoni. When they were both placed into Anolis (details in Nicholson et al.), the more recently named species had to be given a new name, and so it became Anolis etheridgei¸the name it has borne for many years. Now, however, the two species would be placed in different genera, meaning that the species formerly known as etheridgei gets to resume its old name of darlingtoni. Thus, not only we will have two anoles with the last name darlingtoni—Chamaelinorops darlingtoni and Deiroptyx darlingtoni—but keeping track of which one the old name etheridgei applied to will no doubt be confusing. Admittedly, there hasn’t been a tremendous amount of research on these two species, but there has been a little.
5. Finally, on a more colloquial level, members of the genus Anolis are commonly called “anoles,” and sometimes “anole” or “anoline” is used as an adjective. Of course, the rules of nomenclature do not regulate common usage, but with only one genus of eight bearing the name “Anolis,” will the word “anole” also change meaning? And, if so, will this lead to even more confusion? Of course, we can still retain the name “anole” for lizards in the eight genera, but it’s notable that Nicholson et al. frequently refer to all anoles using the term “dactyloid”—in other words, what used to be called “anoles.” The authors at time also use “anole” and I could not discern any rationale for why “dactyloid” was used in some places and “anole” in others (both were used as nouns and adjectives). The confusion has already begun!
In summary, in ways small and large, splitting Anolis into eight genera will be disruptive, impeding public understanding and scientific research. Given that the system is working—indeed, thriving—now, changing all these names will correct a problem that doesn’t exist, at large cost.
KIRSTEN E. NICHOLSON, BRIAN I. CROTHER, CRAIG GUYER & JAY M. SAVAGE (2012). It is time for a new classification of anoles (Squamata: Dactyloidae) Zootaxa, 3477, 1-108
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Skip Lazell
Bravo Jonathan: Right on! Delighted to welcome all you younger folks to The Gorman Club. Anolis sensu lato is in the Iguanidae….
Stuart Nielsen
Well stated, Jonathan! This seems like a perfect job for the Phylocode.
Blair Hedges
Just a quick weigh-in here. As a graduate student, I erected a subgeneric classification for the enormous frog genus Eleutherodactylus sensu lato, and justified that decision based on things discussed in other commentaries here, such as taxonomic stability. In the years since then, I’ve become less enamored with subgenera, and this general approach, for several reasons. First, subgenera are awkward to use, because you must place them in parentheses, and if you want to mention a subgenus in text by itself, you almost always have to preface it with “the Subgenus …” which again makes it awkward to use. And the whole point of a classification, to facilitate communication among scientists about biodiversity, is largely lost because many non-systematists will be unaware of taxa, such as subgenera, that are buried in the literature and not visible as binomials. I also think that large genera can have a somewhat inhibitory effect for future research, taxonomic and otherwise, because they require more time to gain background and expertise on the species. (some of the reasons that I recently jumped on the other side of the fence and broke up the skink genus Mabuya into multiple genera, and proposed a new classification for the goliath family Scincidae sensu lato with its ~1500 sp). As with any classification, it is always up to the community as to whether it is accepted (as was pointed out correctly in these commentaries).
Concerning the recent proposal to break up Anolis into multiple genera, I sense a great resistance now within the anole community. If the users of the classification don’t want it, and don’t need it, then they don’t have to use it. In fact they don’t even have to use the new classification at the subgeneric level–they can simply use the earlier informal nomenclature. I predict that there will be a time in the future when the anole community will feel more comfortable about splitting up the genus Anolis, whether it follows the proposed classification or some other classification. I predict that because I know that the genus will definitely get larger and more difficult to manage than it is already.