Anole Classics: Albert Schwartz (1974) on Geographic Variation in Anolis ricordii

Six years after publishing his impressive monograph on geographic variation in Anolis distichus, Schwartz published a similarly impressive monograph on geographic variation in Hispaniolan crown-giant anoles (Schwartz 1974). At the time this monograph was written, most authorities recognized a single polymorphic species of Hispaniola crown-giant anole with three subspecies: A. r. ricordii, A. r. baleatus, A. r. leberi, and A. r. barahonae (see my previous post on the spelling of ricordii if you’ve seen this name spelled with a single final “i” previously). However, as was the case with distichus, controversy was brewing before Schwartz’s monograph about whether these forms were best recognized at the specific or subspecific level and whether additional distinct forms had yet to be recognized within existing taxa.

Schwartz reviewed the taxonomic history of the Hispaniola giants in the introduction to his monograph. From a relatively small sample of 17 specimens from European collections, Mertens (1939) recognized two “readily distinguishable” populations as subspecies of A. ricordii (A. r. ricordii in Haiti and A. r. baleatus in the Dominincan Republic). Examination of larger series by Williams in the 1960s led to the recognition of two additional subspecies: A. r. barahonae and A. r. leberi. Even with the nearly 200 individuals considered by Williams, however, many geographic gaps remained unsampled and questions remained about about overlap of distinct forms, intergradation and hybridization, and specific versus subspecific status of all four named taxa.

In their 1969 summary of geographic variation of Hispaniola anoles, Williams and Rand suggested that several subspecies of A. ricordii might deserve full species status, most notably A. r. ricordii, A. r. barahonae, and A. r. baleatus. Each of these three could be readily distinguished morphologically by traits like the height of dorsal crest scales, number of scales between the eyes, and body coloration. Moreover, these three taxa appeared to have entirely non-overlapping ranges that were often separated by 100+ km; A. r. ricordii and A. r. leberi, meanwhile, are the only pair of subspecies that appeared to show evidence of intergradation prior to Schwartz’s work. Schwartz’s monograph addressed many lingering taxonomic issues while also describing additional subspecies within some widespread forms by examining 403 preserved specimens, many of which were the result of his own collecting efforts.

Schwartz recorded data on 20 phenotypic traits from all 403 specimens, including body size, numerous scale counts, and several aspects of coloration. Schwartz elevated the three phenotypically distinct and seemingly geographically isolated subspecies (ricordii, barahonae, and baleatus) to full species status, resulting in a ricordii species group including three species. Anolis ricordii and A. baleatus have broad distributions on Haiti and the Dominican Republic, respectively. Anolis barahonae is restricted to upland habitat on the Barahona Peninsula. Schwartz’s decision to elevate these taxa was inspired in part by the fact that he had previously teamed with Garrido to divide the Cuban trunk-crown anoles related to A. equestris into a number of disinct species. Although there were no instances of sympatry between the Hispaniolan forms (as was occassionally the case on Cuba), the Hispaniola species exhibited striking phenotypic differentiation that rivaled that of their Cuban counterparts. Schwartz viewed the differences between A. ricordii and A. baleatus as unequivocal and fairly obvious, but found it somewhat more difficult to distinguish A. baleatus from A. barahonae. He likely would have considered them conspecific were it not for the facts that (1) these taxa appear to be entirely allopatric and (2) A. barahonae is geographically closer to populations of A. ricordii than it is to any populations of A. baleatus.

Within the largely Haitian range of A. ricordii, Schwartz would recognize four subspecies: A. r. ricordii, A. r. leberi, A. r. viculus (subsp. nov.), and A. r. subsolanus (subsp. nov.). In most cases, these subspecies were geographically isolated based on the sampling available to Schwartz at the time. Indeed, Schwartz notes that he “would be very tempted to consider” leberi, viculus, and subsolanus distinct species were it not for the presence of putative intergrades between ricordii and viculus in the Miragoane-Paillant-Fond des Negres region.

Within the Dominican Republic’s most widespread species, Schwartz recognized eight allopatrically or parapatrically distributed subspecies: A. b. baleatus, A. b. multistruppus (subsp. nov.), A. b. sublimis (subsp. nov.), A. b. caeruleolatus (subsp. nov.), A. b. samanae (subsp. nov.), A. b. litorisilva (subsp. nov.), A. b. scelestus (subsp. nov.), and A. b. fraudator (subsp. nov.). All of these subspecies were diagnosed based on differences in both scalation and color. Although the scope of Schwartz’s sampling was impressive, considerable sampling gaps existed between most of Schwartz’s subspecies and some where known definitely from only one or two localities. Partly due to these gaps in his sampling, Schwartz often inferred, but rarely observed, intergration.

In the Barahona Peninsula dwelling A. barahonae, Schwartz reluctantly recognized two subspecies: A. b. barahonae and A. b. albocellatus. Although Schwartz seemed confident that these taxa were distinct based on both phenotypic and habitat data, his description of A. b. albocellatus was based on only a single specimen from a single locality.

As he had done with distichus, Schwartz also commented extensively on the biogeographic history of the ricordii species group. Schwartz hypothesized a north paleo-island origin for the Hispaniolan giants, followed by two separate invasions of the the south paleo-island (by A. ricordii and A. barahonae).

Not much work has been conducted on the ricordii species group since the publication fo Schwartz’s monograph. This is likely due largely to the fact that giant anoles are harder to observe and sample than are other types of anoles. Nearly all of the specimens examined by Schwartz were obtained at night, when sleeping animals can be obtained relatively easily in the right type of habitat. The group is clearly ripe for further study, and application of molecular genetic data to Schwartz’s hypothesized taxa in particular.