Nicholson 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