Evolutionary Taxonomy Meets Phylogenetic Systematics: Maybe 8 Genera Isn’t Enough for Anoles

There’s an old saying, “life imitates art.”

The last few days have seen renewed discussion of the proposal to split Anolis into multiple genera. In their most recent paper, Nicholson et al. (2014) explain why they want to split up Anolis: “Starting with Savage (1973), we have made clear our conclusion that the beta section of Williams (1976) deserves generic status (Norops).” The reason, as they explain in the preceding paragraph: “Anyone who has caused a squamate’s tail to separate from its body, and has read Etheridge’s paper, understands immediately why we conclude that the beta condition within anoles is as important to understanding the diversity of that group as the toe lamellae of anoles is to understanding the evolution of Dactyloidae.” In other words, the caudal vertebral structure of Norops, “a derived condition of the caudal vertebrae unique among squamates,” is so notable and distinctive that Norops needs to be recognized as a genus to call attention to and emphasize this evolutionary transition.

This approach follows the rationale of Ernst Mayr’s Evolutionary Systematics Classification system, whose goal was to highlight major evolutionary transitions. This approach has generally fallen out of favor, however, because it often led to the recognition of paraphyletic groups, such as “reptiles,” when birds are elevated due to their evolutionary significance.

Nicholson et al. (2014) solve this problem, however, by recognizing the clade they consider important, Norops, but then recognizing as many other clades as necessary to render all clades monophyletic: “Therefore, the seven additional genera that we propose as replacements for the alpha section represent the minimum number of genera needed to eliminate the problem of the previous taxonomy” once Norops is elevated to generic status. Evolutionary classification meets phylogenetic systematics!

Surely if one clade of anoles is going to be recognized at the generic level because it has a funky tail, then Chamaeleolis deserves to be a genus as well.

Nicholson et al., however, are not the first to take this approach in revising anole classification. Just last year, another paper considering anole classification came to exactly the same conclusion. Dimedawter et al. (2013), writing in Nature Herpetology, propose: “This approach is implemented readily enough and entails nothing more than identifying evolutionarily important clades, recognizing them at the appropriate taxonomic level, and then revising the remaining taxonomy to ensure that all taxa are monophyletic.” Taking the approach to its logical extreme, they then illustrate it using Anolis. However, rather than Norops, Dimedawter et al. start with Chamaeleolis and Chamaelinorops, two clades so distinctive that the authors contend they should be recognized at the generic level, as they once were.

No toepads? That’s got to be its own genus.

But what constitutes evolutionary significance is in the eye of the beholder. Dimedawter et al. survey anoles and note a number of other clades that seem distinctive enough to warrant generic recognition. Among these are the padless anole of Venezuela (Tropidactylus); twig giants and dwarves of South America (Phenacosaurus); the aquatic anole of Hispaniola (A. eugenegrahami); Xiphocercus, the medium twig anole of Jamaica; Deiroptyx as originally constituted (vermiculatus and bartschi); among others. All of these anoles are cool and distinctive in their own way, and so it seems reasonable to recognize them as distinct genera. In sum, they identify 11 clades worthy of generic level designation. To maintain monophyly of all anole clades, that requires recognizing 34 more clades, for a total of 45 anole genera.

Dimedawter et al. then go one step further. Agreeing with Nicholson et al. (2012), they argue that phylogenies should be informative of phylogenetic relationships. However, they fault Nicholson et al. for not going far enough—after all, their proposal does not provide insight on the relationships among the 150 Norops, or even among the six Chamaeleolis in their own system. So, they propose a new approach, Maximally Informative Phylogenetic Clustering (MIPC), which allows one to always know the sister taxon of a species from the classification. Applying this approach to anoles, they propose the recognition of 133 anole genera.

Exciting times for anole classification!

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.

4 thoughts on “Evolutionary Taxonomy Meets Phylogenetic Systematics: Maybe 8 Genera Isn’t Enough for Anoles

  1. The pet trade will be best served when every species is in its own monotypic genus, and academic tenure and pay depend greatly on peer-reviewed publications. It’s all done for the money. Skip

  2. I’m a little concerned that ridiculing any attempts to change taxonomy in anoles might polarize views to an extent that a well-reasoned compromise is not possible.
    As Rich Glor recently posted in his response, the use of sub-genera would help anyone using them to have both the benefits outlined by Nicholson et al. without disrupting the taxonomy. (See David Wake’s original 2012 post making the suggestion).
    I would really like people to embrace this suggestion. The problem is getting researchers to use sub-genera. Anolis series are still in usage in the literature, in spite of the fact that many of them are demonstrably non-monophyletic (or in many cases, monophyletic if you swap species x for species y as they were originally defined).
    I think 8 subgenera is a good place to start, and a formal redefinition of Anolis series would be a good follow-up. Subgenera also act as a compromise between those wanting to abandon Linnean taxonomy.
    Another point, I’m pretty sure that many readers of Anole annals are unaware of the extent of this joke.
    That Nature Herpetology does not exist, that all of the names and the Universities mentioned are based on the actual authors, etc. (e.g. Kirsten E. Nicholson = Katherine E. Dimedawter — Nickel Son = Dime Daughter, get it?).

  3. I can’t believe how childish this is, and that the hosts of Anole Annals would support this hoax posting. Wow.

    1. I honestly don’t understand the incredulity. Multiple arguments have been put forth against the Nicholson et al. (2012) treatment and most seem to acknowledge the work was severely flawed on multiple levels. Those arguments have not been suitably answered by the Nicholson et al, who seem to brush aside the philosophical aspects of the discussion entirely. The Dimedawter et al. paper (while a joke) makes light of the proposed changes and demonstrates the absurdity of subjective taxonomic treatments such as that suggested by Nicholson et al. In my opinion, it demonstrates that absurdity in a very effective way, potentially to those out there that would not otherwise easily grasp the reasoning.

      Say there were no problems with the monophyly of clades, the synapomorphies, etc. Using the same reasoning expressed in Nicholson et al., systematists will continually split each of those 8 clades into more genera. Yes, even (especially) Norops would fall victim to this, as expressed by Poe in his response. But what does the scientific community actually gain from this approach, and when does it stop?

      While it may be upsetting to the original authors of Nicholson et al, the Dimedawter paper serves a real purpose. Furthermore, this is a blog. It shouldn’t be surprising that a paper as roundly criticized as Nicholson et al. would get a variety of responses, and incorporating humor is to be expected.

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