New Paper Supports Proposal to Split Anoles into Eight Genera

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We had plenty of discussion a couple years back about the proposal to divide Anolis into eight genera. The debate seems to have quieted down without clear resolution. Now, in a new paper on Mesoamerican herp conservation, Johnson and colleagues come out in favor of the Nicholson et al. proposal. I’ll place their commentary below, but I want to address a point they raise at the end of their discussion.

Johnson et al. conclude: “We agree that Nicholson and her coauthors provided a perceptive set of reasons why their classification will be accepted in time, just as with other classifications that sought to make sense of formerly unmanageable genera, such as Eleutherodactylus , which now not only is segmented into a number of genera, but also a number of families.”

This is not the place to discuss or debate these points, which have been thoroughly aired in previous commentary in these pages [e.g., 1,2]. But what about the authors’ suggestion that this new classification will be accepted in time? Is that happening?

It’s hard to assess how the winds of systematic practice blow, but I took a crack using Google Scholar, restricting my search to the years 2014 and 2015. When I queried how many hits there were for “Anolis,” GS returned (searched on August 14, 2015): “about 2600.” For Norops,  “about 110.” Can we conclude that represents a 24-fold preference for the old taxonomy over the new one? Of course not. For one thing, some of those Anolis papers may have been referring to species that would still be Anolis in the new classification, most notably A. carolinensis.

I then tried again, focusing on probably the most studied species that would change its name in the new classification, Anolis (Noropssagrei. In this case, for the same 2014-2015 period,  GS located 16 hits for Norops sagrei vs. 270 for Anolis sagrei. These results would seem to indicate that the new classification system hasn’t penetrated very far into the broader scientific community.

One clear schism in the anole community is between those scientists who work in the West Indies, who overwhelmingly use the name Anolis, versus those in Central and South America, who are more split. So, as a second test, I looked at what I think may be the most frequently referred to mainland anole, A. limifrons. The GS search in this case yielded six hits for N. limifrons and 22 for A. limifrons. Searching on the species chrysolepis gave a comparable result, 29-8 in favor of Anolis (and proving that my guess was wrong about which species is most discussed in the literature). Still a large preference for the established taxonomy, but only a 4:1 ratio compared to sagrei‘s 17:1 ratio.

Of course, there are much more sophisticated ways of addressing their question, but they would take a lot more time. Anyone want to dig further?

 

Here’s what the authors have to say (broken into paragraphs for easier reading):

A sizeable number of herpetologists are interested in anoles and their classification. Over the years, many herpetologists have tried to make sense of a group of lizards that presently contains 395 species (Reptile Database website; accessed 28 February 2015), with more added each year (e.g., see our listing of presently added taxa to the Central American herpetofauna, in which we document the recognition of 15 additional species-level taxa since the publication of Wilson et al., 2010). Gunther Köhler and his colleagues undertook most of this work and with one exception (Dactyloa ginaelisae) described or resurrected the remainder under the genus Anolis. In our present work, we list 95 species of anoles in Central America, and Wilson et al. (2013a) recorded 50 species from Mexico; presently 129 species comprise the anole fauna of Mesoamerica (16 species occupy both regions; www.mesoamericanherpetology.com; accessed 28 February 2015). In Wilson et al. (2013a), we listed all 50 Mexican species under the genus Anolis. We took that position because a controversy was brewing over the classification proposed by Nicholson et al. (2012), especially with the harsh rebuttal of this paper by Poe (2013), and we were uncertain where the controversy would go. Since that time, however, Nicholson et al. (2014) provided a detailed response addressing Poe’s concerns.

Most anyone with an interest in anole systematics knows the backstory, beginning with Guyer and Savage’s (1986) revolutionary cladistic analysis of the anoles. The effect of that study was to segment the huge and unwieldy genus Anolis into a series of eight genera. Subsequently, Williams (1989) authored a scathing critique of the Guyer-Savage approach, asking if the data were available to reclassify the anoles; herpetologists varied in their opinions. During the ensuing years, students of tropical American herpetology basically fell into two camps, those who supported or opposed the Guyer-Savage scheme. In recent years, we sided with the latter camp (Wilson and Johnson 2010; Johnson et al. 2010; Wilson et al. 2013a), but did not undertake an exhaustive study of the matter.

Nonetheless, after the publication of Poe’s (2013) critique of the Nicholson et al. (2012) paper and the Nicholson et al. (2014) rebuttal, we decided to take a fresh look at this issue. Principally, the controversy that developed over the last two years results from two approaches to the classification of anoles. The Nicholson et al. (2012, 2014) approach was to recognize eight genera of these lizards. Poe’s (2013) tactic was to jettison entirely the Nicholson et al. (2012) approach and to recognize a single genus that contained 391 species, the largest genus of squamates.

Fundamentally, Poe’s criticism of the eight-genus approach was two-fold, i.e., that “some of the proposed genera are not monophyletic” and that Nicholson et al. (2012) did not study enough taxa or enough characters. Nicholson et al. (2014) presented their rebuttal “to explain how Poe erred in characterizing our work, and missed the opportunity to present an alternative comprehensive taxonomy to replace the one against which he argues so strenuously.

In this contribution we explain, and correct, Poe’s errors and misrepresentations, and argue that our taxonomy is likely to be adopted because it (1) eliminates the obvious problem that will arise if the family Dactyloidae contains only a single large genus (i.e., that a single genus obscures the evolution and diversity within the group and misrepresents or cloaks it), (2) it conforms with the long historical trend of dissecting large, cumbersome groups into smaller sub-units, (3) is consistent with all recent phylogenetic studies for anoles in membership within clades we recognize as genera, and (4) aids in associating these lizards with the ancient land masses that shaped their history.”

We consider that Nicholson and her coauthors adequately responded to Poe’s criticisms and we are confident in adopting the portion of their scheme relevant to the situation in Central America, and Mesoamerica as a whole. So, what impact does the Nicholson et al. approach have on the taxonomy of anoles in Mesoamerica? As it turns out, only three of the eight genera Nicholson et al. (2012, 2014) recognized contain Mesoamerican species as follows: Anolis (one species), Dactyloa (10 species), and Norops (118 species)…

 

About Jonathan Losos

Professor and Curator of Herpetology at the Museum of Comparative Zoology at Harvard University. I've spent my entire professional career studying anoles and have discovered that the more I learn about anoles, the more I realize I don't know.

9 thoughts on “New Paper Supports Proposal to Split Anoles into Eight Genera

  1. The following statement indicates a refusal to address the most important part of the Poe (2013) rebuttal:

    “Fundamentally, Poe’s criticism of the eight-genus approach was two-fold, i.e., that “some of the proposed genera are not monophyletic” and that Nicholson et al. (2012) did not study enough taxa or enough characters.”

    In a perfect scenario with complete sampling and a fully-supported phylogeny, the subjective (=non-scientific) nature of the splits is as much a reason to reject the Nicholson (2012) classification as any. See Pauly et. al. (2009), “Taxonomic freedom and the role of official lists of species names” for further discussion of problems that can arise from unnecessary taxonomic changes.

  2. Splitting primarily benefits the pet trade, where nifty new names sell a lot more lizards. Of course publishing ANY peer-reviewed paper benefits the authors if they are in a system where publication leads to rank and pay increases. I totally oppose this splitting. Always have…. Skip

  3. The main question, to me, is: is the split needed? I.e., is there a compelling argument against one big genus Anolis? When the arguments in favor of the split are only that, all else equal, the “new” nomenclatural would be better, I tend to think inertia wins, or should win. All else is not equal. Change in and of itself carries a cost. Particularly when we’re talking about a genus associated with a large body of research, we need to know that the benefits of the change justify the cost. So long as we’re dealing with optional changes in nomenclature, I don’t think that burden is met.

    That said, nomenclatural change is a very slow process. In the botanical world, one of the genera I’ve worked on was proposed as a new genus back in 1976. At the time, evidence that the split was necessary (not optional, but necessary) was suggestive, but not conclusive. By 2003, the evidence was clear-cut and most of the needed nomenclatural changes were published as a result. By 2015, we still have to talk about it as a “new” genus and explain that these taxa species used to be included in the “old” genus but that numerous phylogenetic studies have shown this is not workable. The “new” genus is in very few of the floras used by field botanists and hasn’t remotely percolated into the world of ecology. By 2025, I assume (or hope) this change will be broadly accepted and part of the traditional nomenclature. But we still have nomenclatural changes that were well-supported in the 1980s that haven’t been accepted by ecologists, so who knows! So, supposing the split of Anolis is accepted in the long-term, expect it to dominate in the non-taxonomist literature by something like 2035 or 2040. Of course, various political factors can speed up the process considerably, if an influential group of scientists advocates for the adoption of a particular nomenclatural arrangement. Yes, I’m thinking of the SSAR list. Even so, as an example, academic article references from 2014 to present to Elaphe obsoleta outnumber those for Pantherophis obsoletus, Elaphe alleghaniensis, Pantherophis alleghaniensis, Elaphe spiloides, and Pantherophis spiloides combined–by something like 3 to 1. And that’s fifteen years after a split that had THE academic society for these critters backing it. The gist is, if you want to know if a nomenclatural change will stick, don’t look at the literature now. Look at the literature 20 years from now.

    1. If any nomenclatural change is going to be accepted, it’s going to happen v e r y s l o w l y.

      We might not even live to see it happen. Your children might still be learning about is as “the new name”…

  4. Anolis is a valid name for a monophyletic group on the Tree of Life. It is “special” as a genus only in that the genus name is used as part of a binomial for particular species. It doesn’t make sense to change the scope and application of generic names unless the names are actually misleading about phylogeny (e.g., if Anolis were polyphyletic, then that problem should be fixed). But splitting a valid, monophyletic genus into a bunch of smaller genera, and thereby needlessly changing the names of many species, without fixing any phylogenetic problems with the existing taxon names, is not science. It is just playing around with names. If someone wants to name the groups within genera, then do so…but there is no reason to change the meaning of a existing name (or the names of the all the affected species) in doing so. That is the kind of silliness that gives taxonomists such a deservedly bad reputation among biologists.

  5. This seems more like a sociological matter.

    During the ‘taxonomic revolution’ of the amphibians, about 10 years ago, the (perhaps?) most influential (or faster?) group was the splitter one, and their taxonomic scheme prevailed. Currently, nobody is upset about which species were once named as Bufo, Hyla or Rana. A few do care about Dendrobates – like Anolis, a sexy group with a body of dedicated investigators.

    It seems that a single genus makes sense for the community that investigates dactyloid lizards more closely. On the other hand, those who deal with overwhelming levels of herpetological diversity in the tropics (waaaay beyond lizards) see benefit in more partitioned schemes, which correlate more closely to morphology and geography.

    So, when we discuss names, it may be healthy not to forget about our diversity as investigators as well. About science, splitting Anolis is not science, but well, not splitting Anolis isn’t science either.

    1. That remark that “nobody is upset about which species were once named as Bufo, Hyla or Rana” is funny! In fact, about 93% of the scientific papers on Rana pipiens since the proposed name change to Lithobates have continued to use the name Rana pipiens, and similar ratios apply to the other affected species. The vast majority of people have NOT recognized the proposed change to Lithobates, as they shouldn’t. The proposed change made no sense…the genus Rana (in the sense that includes Lithobates) is monophyletic in ALL analyses, whereas splitting it into Rana and Lithobates creates new problems where none existed. In addition, it needlessly changes numerous well-used species names, including those of several model organisms. The proposal would also change the meaning of both Rana and Lithobates. The overwhelming majority of people who work on the systematics and biology of Rana (including me) continue to use Rana as the correct genus for all the New World species. Hyla was a different matter…some species, such as “Hyla crucifer”, made Hyla polyphyletic. Removal of those species was the easiest way to fix a phylogenetic problem. Bufo continues to be the most controversial, with people arguing both sides. There are indeed monophyly issues, and so the question is how to best fix these in the least disruptive way. It isn’t clear yet how this will fall out.

    2. Unfortunately, the genus category (and above) seem to be more arbitrary than the species. Attempts to use a time-based criterion failed (in mammals apparently no so much).
      The comment that splitting Anolis reflects better morphology and geography is also arbitrary, because we end up with the question “how much different do they need to be?” or “how much difference is enough?”, also this precludes highly autapomorphic taxa inside a clade.
      Also, why categories nested inside genera are not used? maybe that is because of tradition and “sociology”. But subgenera or species group, because they are subcategories within genera, reflect the actual phylogeny much better than full genera.

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