Anolis: Should It Stay Or Should It Go?

ResearchBlogging.orgNicholson et al. recently undertook the bold mission of revising the taxonomy of our well-loved lizard genus, Anolis, based on the phylogenetic relationships among its many species. Not surprisingly this has struck a nerve with much of the anole community spawning a range of reactions immediately following its publication, some applauding their efforts but many expressing their concerns about the proposed change. If one of the author’s objectives was the generate discussion on this topic its clear that they have succeeded.

The Nicholson team should first be commended for their efforts to synthesize the historical literature on anole taxonomy, encompassing “387 recognized species and 112 additional nominal subspecies” with some reports dating as far back as the mid-1600s. This survey will likely serve as a benchmark for later systematic evaluations of this genus. However, the implications for their proposed revision extend well beyond the nuances of taxonomic rule or the analytical methods used to build phylogeny*. The issues arising extend into other biological disciplines and potentially undermine the rich intellectual history of anoles.

I, like many others, am a consumer of taxonomy and systematics. These are critical to the comparative analyses I perform and in communicating my findings to others in the anole community, herpetologists more generally, and other biologists more broadly still. Anolis has been a model for comparative biology for decades but is gaining increased attention by genomicists, neuroendocrinologists, and developmental biologists. Just this year, in fact, the anole community developed a system with which to share comparative molecular resources. Deconstructing Anolis into eight distinct genera could drive an intellectual wedge between the previously published literature and future studies, potentially derailing the continuity of information that is critical for academic advancement. This change could lead to unforeseen consequences that damage the broad utility of Anolis among biological disciplines that depend on the stability of anole nomenclature.

Nicholson et al. state, “the role of systematics is to advance our understanding of biological diversity.” While I agree with this statement in principle I feel that it is also important to ask if the benefits of revising this diverse taxon outweigh the risks I outlined above. The glaring disconnect between phylogenetic systematics and Linnean ranks is discussed at great length elsewhere and will be strategically avoided here. It is worth asking, however, whether the addition of new genera (specifically genera, not simply clade names) add anything new to our biological understanding of this group. Ultimately, can we more accurately communicate our findings using the revised nomenclature? While Nicholson et al. use monophyletic clades to distinguish the proposed genera  – a well respected practice – the precise breaks are biologically arbitrary. In my opinion the suggested genera do not offer greater clarity to the natural history of this clade as they do not partition Anolis based on distinct biogeographic groups, groups with distinct ecologies, or groups with distinct, readily recognizable morphological features. In this proposed taxonomic scheme the ecological and morphological convergence of Anolis ecomorphs** that is widely discussed and cited throughout ecological and evolutionary literature becomes a confusing hodgepodge of convergent lineages from different genera. In my opinion it is overwhelmingly clear that the benefits of re-classifying Anolis lizards do not outweigh the ensuing upheaval of our research community.

At face value it appears that the overall motivation for revising Anolis is its diversity, as it is undoubtedly one of the most diverse tetrapod genera. However Anolis pales in comparison to many invertebrate genera. The beetle genus Agrilus (jewel beetles) has an estimated 2886 species! Drosophila – the genus that possesses the genetic and developmental powerhouse D. melanogaster – contains approximately 2000 species***. It is clear that large, active research communities can readily work with diverse genera without problematic communication of their results. The sole argument of diversity is not strong justification for revising Anolis.

Perhaps some day taxonomy will abandon the binomial naming scheme derived from the Linnean classification hierarchy in favor of a more accurate system based solely on phylogenetic systematics. However, for practical purposes, we are simply not there yet. Anolis serves as a great example of where premature taxonomic revision could have far reaching consequences that can send biological research in multiple disciplines into severe turmoil.

Comments and discussion on the ideas I have shared above are welcomed and encouraged!

* This is not the say that critical evaluation of phylogenetic methods are not essential to the evaluation of taxonomic hypotheses. I will save evaluation of the Nicholson et al. analyses to those with greater experience working this these methods and those with an intimate knowledge of the proposed species groups.

** Beyond their proposed taxonomic revision the Nicholson team also reject the Anolis ecomorph concept. This idea will no doubt attract additional attention from the community.  Stay tuned to Anole Annals for more on this issue.

*** A similar discussion to ours recently took place in the Drosophila community and many of these same concerns were expressed. O’Grady and Markow 2009 state that “such radical taxonomic revision is not advisable…as the literature and traditions are
so well established that any such formal reassessment would not be worth the confusion engendered.” After review and comments from the community the ICZN voted that taxonomic revision of Drosophila was “premature” and wisely left this diverse genus intact.
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

About Thomas Sanger

Thom Sanger is an Assistant Professor at Loyola University in Chicago. His lab specializes on understanding the developmental bases of Anolis lizard diversity.

6 thoughts on “Anolis: Should It Stay Or Should It Go?

  1. I think Thom brings up many good points. In addition to the potential confusion that name changes could cause in the literature, there’s also the danger of causing confusion in major databases, which are valuable community resources. For instance, GenBank contains almost 200,000 total Anolis sequence records, and the HerpNet database contains over 160,000 Anolis museum records. Modern databases can usually be updated to accommodate changes, but there’s always the chance that errors will arise and confusion can result during the transitions. Plus, large databases already take a lot of work to maintain and administer and updates take time – time which could be better spent improving features and accessibility.

  2. This is a quick note of clarification on Thom’s footnote related to the ICZN’s ruling on Drosophila and specifically on his remark that “After review and comments from the community the ICZN voted that taxonomic revision of Drosophila was “premature” and wisely left this diverse genus intact.” This remark incorrectly implies that the ICZN has a role in making taxonomic decisions, rather than just nomenclatural decisions. The ICZN has no interest in legislating taxonomy and they did not attempt to do so in the case of Drosophila. The only role the ICZN has is to govern the names that are applied to taxa diagnosed by Drosophila systematists (i.e., nomenclature). The problem faced by the community of people working with Drosophila melanogaster is that Drosophila does not appear to be monophyletic and some members of the Drosophila systematics community have suggested that this problem might be solved by dividing species from Drosophila into a bunch of monophyletic genera. This could lead to a change in the name of Drosophila melanogaster because this species belongs to the subgenus Sophophora and does not appear to be closely relate to the type species of Drosophila. Therefore any formal generic revision would likely involve applying the generic epithet Sophophora to the species that is recognized in tens of thousands of published reports as Drosophila melanogaster. The folks who are interested in such a generic revision sought to avoid the chaos that would result from such a change by petitioning the ICZN to make Drosophila melanogaster the type species for the genus Drosophila. If the ICZN had approved this petition, a generic revision that divided a paraphyletic Drosophila into multiple genera could have been implemented without necessitating a change in the name Drosophila melanogaster. The ICZN rejected this petition. However, this does not mean that the name of Drosophila melanogaster needs to be changed to Sophophora melanogaster. Even if such a name change is formally proposed, the Drosophila melanogaster systematics community will need to evaluate the new taxonomic arrangement and may ultimately arrive at an alternative solution (i.e., applying Drosophila broadly to include those taxa that once rendered this genus paraphyletic [although I don’t know enough about this situation to know if Drosophila would have priority over other generic names]). There is one important point that you should extract from this comment regarding our ongoing discussion of Anolis: the ICZN does not legislate taxonomy and because the continued use of Anolis for all anoles does not violate any of the ICZN’s articles governing nomenclature, the ICZN has no role whatsoever in deciding whether we continue to use Anolis or adopt Nicholson et al.’s proposed generic revision.

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