Few anole species have been responsible for as much taxonomic confusion as the widespread Amazonian species Anolis chrysolepis. It wasn’t even until 2008 that taxonomists decided once and for all that this species should be called A. chrysolepis (Duméril & Bibron 1837), rather than A. nitens (Wagler 1830) (Mayer 2008 successfully petitioned for recognition of A. chrysolepis on the grounds that Wagler’s Draconura nitens was a nomen dubium due to the absence of a holotype and an exceptionally vague 4-line description and locality [“America”]).
Largely because of its broad range and remarkable geographic variation in size, shape, and coloration, Anolis chrysolepis has attracted the attention of herpetologists for generations. It even became a flashpoint for debate about the role of Pleistocene refugia in tropical diversification when Vanzolini and Williams (1970) suggested that the group’s geographic diversity could be explained by this phenomenon. Although a previous molecular phylogenetic analysis (with very limited sampling) rejected Pleistocene diversification by implicating considerably more ancient processes, this study only strengthened the view that populations of A. chrysolepis that have long been recognized as subspecies might warrant elevation to full species status. Now, D’Angiolella et al. (2011 [PDF]) have given A. chrysolepis a long-deserved comprehensive genetic and morphological treatment, and conclude that the each of the five currently recognized subspecies should be elevated to full species status.
D’Angiolella et al.’s (2011) study is among the finest work on intraspecific variation in any anole species, and involved examination of hundreds of individuals from across the range of A. chrysolepis. Their molecular phylogenetic dataset includes new sequence data from the mitochondrial genome for 39 individuals from 34 localities (to go along with 14 samples from the previous study). Even more impressively, D’Angiolella et al. (2011) obtained morphological and morphometric data from over 400 museum specimens.
Their molecular and morphological results identify six species as members of the A. chrysolepis species group, including five species previously regarded as subspecies of A. chrysolepis (A. basiliensis, A. chrysolepis, A. planiceps, A. sypheus, and A. tandai) and one additional species (A. bombiceps). Their molecular phylogenetic analyses also suggest that a seventh species – A. meridionalis – likely also belongs to the A. chrysolepis group, but the status of this species remains in question because phylogenetic support for its nestedness in the A. chrysolepis group is weak.
Molecular phylogenetic analyses further suggest the existence of two well-supported clades within the A. chrysolepis group, one with two species (A. chrysolepis and A. c. tandai) and another with three species (A. c. basiliensis, A. c. planiceps, A. c. sypheus, and A. bombiceps). All of the species in these clades are deeply genetically divergence (>10% uncorrected sequence divergence, corresponding with millions of years of evolutionary separation). All of these species can also distinguished by morphological and meristic data, although D’Angiolella et al. (2011) did not use phylogenetic methods to infer species level-relationships on the basis of morphological variation.
Many studies that propose elevation of subspecies do so without providing new descriptions of the taxa in question, presumably because one can always refer to the original subspecies descriptions. D’Angiolella et al. (2011), however, go the extra mile by providing abbreviated descriptions of each species in the A. chrysolepis group, as well as a key to distinguishing among them. In their descriptions, they include notes on coloration of the body and dewlap in life an preservative. The one thing missing from each individual species accounts is some information on ecology and natural history. I also would have liked to seen publication of georeferenced locality information (the localities in the paper are descriptive and lack precise coordinates), but this is another relatively minor shortcomings. Hopefully forthcoming studies will begin to fill in some of the blanks.
A thorough taxonomic treatment of A. chrysolepis is long over-due, but I’m happy to report that D’Angiolella’s (2011) report was worth the wait.