Anolis oculatus, the Dominica anole, Dominican anole, eyed anole or zandoli, is a species of anole lizard. It is endemic to the Caribbean island of Dominica, where it is found in most environments. The species is found in a diverse range of color forms, which one herpetologist once classified as four subspecies, which most other scientists did not recognise because the forms gradually inter-grade with one another. Two later researchers have instead promoted the "ecotypes" concept, hypothesizing the color forms are maintained by the ecological conditions of the surrounding environment, despite being genetically indistinguishable. The morphology of some traits is subject to clinal variation, gradually changing from one side of the island to the other, or from sea level to the hilltops. The ground color ranges from pale tan or yellow to deep green or brown. It also has patterned markings that range from light-colored speckling to complex marbled patterns, and some populations also have large black-ringed "eye" spots on their flanks.
The Dominican anole spends much of the time in trees but mainly hunts on the ground. Small insects make up the bulk of its prey, with soft-bodied invertebrates and small vertebrates hunted less frequently. Long-living and late maturing for anoles, the Dominican anole can usually breed from around two to three months of age. Females lay eggs, and breeding can occur at any time of year. Clutches number one or rarely two eggs and are laid under rocks or leaves on the ground. Although presently widespread and common on Dominica, in 2007 some authors opined that it may face competition from A. cristatellus, an anole from Puerto Rico, which was introduced a few years earlier.
History and taxonomy
The Dominican anole is locally known as the zandoli, or tree lizard.; . Also spelled "zanndoli". The indigenous Island Caribs considered its presence in their home to be a sign of "good spirits" according to Honychurch.
According to Malhotra and Thorpe the American paleontologist and herpetologist Edward Drinker Cope gave a cursory description of Anolis alliaceus in 1864, which now seen as a synonym of the species A. marmoratus from another island, on the basis of sixteen specimens at the British Museum that lacked locality data. He later separately described Xiphosurus oculatus in 1879, from thirteen specimens in the U.S. National Museum (now the Smithsonian); the name oculatus (Latin, "eyed") refers to its distinctive lateral spots. The two taxa were synonymised in 1888 by the German-British zoologist Albert Günther.
Because of the variation in colour there was some question as to whether the Dominican anole comprised multiple species or only one.Garth Underwood wrote in 1959, regarding the widely varying specimens he examined, that "[a]fter two visits to the island and examination of more than sixty preserved specimens I remain uncertain about the situation in Dominica... Clearly Dominica will require further careful examination." . The American herpetologist James D. Lazell, Jr. attempted to explain this variation in a 1962 publication. In 1959 he had travelled on foot or on horseback throughout the island, collecting over 500 specimens from thirty localities on Dominica. From this, he concluded that it was a single species, and accounted for its variation by classifying the spectrum of different color forms as four subspecies organised by region: A. o. oculatus, found along the southwestern coastal area, with a holotype from the capital of Roseau (most closely corresponding to the original type described by Cope); A. o. cabritensis, along the northwest coast, with a holotype from the Cabrits peninsula (now Cabrits National Park); A. o. montanus, in central, high elevation rain forest, with a holotype from Fresh Water Lake; and A. o. winstoni, along the northeast coast, with a holotype from the village of Woodford Hill. Detailed descriptions of the coloration and markings of each described subspecies, along with type specimen data, is provided in , with a Table of Diagnostic Characters at p. 475 cataloguing variations in throat fan (dewlap) color, white dorsal spotting, black pigment areas, ground color, venter (belly) color, tail crest, and maximum snout-to-vent length (SVL). The SVL numbers should be considered inaccurate or incomplete, however, as Lazell later noted that he had incorrectly omitted larger specimens. See . These first descriptions applied only to males, however, and omitted certain morphological features such as scale variation. Lazell returned to Dominica in 1966 to collect new specimens, and in 1972 supplemented his original descriptions, including color illustrations of sexual dimorphism among the types..
Lazell noted that the subspecies he described corresponded with the "strikingly different" ecological zones on Dominica, which result from the elevations on the small island interacting with prevailing winds to produce varying rainfall and vegetation.; . Later morphological and molecular studies determined, however, that there was no interruption to gene flow between the different populations, but instead clinal variation where individual lizards differed incrementally from each other to produce very different forms from one end of the island to the other.; ; . Researchers have, therefore, determined that there is no basis for the use of subspecies nomenclature. "Consequently, meaningful definition of boundaries between subspecies is difficult". The former subspecies have been described as "ecotypes" by Malhotra and Thorpe based on their geographic range: the south Caribbean ecotype corresponds to the former A. o. oculatus; north Caribbean ecotype to A. o. cabritensis; montane ecotype to A. o. montanus; and Atlantic ecotype to A. o. winstoni.See for photographic comparisons of these ecotypes for both males and females.
Description
The Dominican anole is medium-sized for anoles, with a maximum snout-vent-length (SVL) in males of depending on the population (with larger sizes correlating with higher altitudes), and tails of at least equal length; females are smaller in all populations.Descriptions are given in ; ; ; ; and . See also photographs in , and color plates in , illustrating the subspecies as he defined them. See , discussing the relationship of male body size to altitude, and noting that size at lower altitudes may be constrained by the higher occurrence of predation in lower coastal areas and by the available food supply. Adult males have a tail crest and a prominent, extensible throat fan that is often a bright yellow or orange. The throat fan is only rudimentary in females, and less brightly colored. Some may have bright blue eyes.. Dominican anoles are capable of slight color change, but not as much as some other anoles..
Their ground color varies from pale tan or ash gray to deep brown or green. Markings also vary significantly. Adult males in all populations have some combination of white or light-colored spotting distributed over most of their bodies. This manifests in different populations as small, evenly distributed spots; scattered groups of white scales; or streaks that run together in a marbled appearance. Males in some populations additionally have larger lateral spots ringed by irregularly shaped black splotches. Markings on females and juveniles are significantly lighter or less distinct, and black spots are extremely uncommon. Females and juveniles may additionally have lateral streaks or mid-dorsal stripes.
The cause of the variability of the anole has been the subject of much study.. Its morphological traits vary independently from each other, such that the presence of one trait does not predict the presence of another. Some traits vary altitudinally and others longitudinally, or may correlate with ecological factors such as rainfall and vegetation type.; . Populations in drier habitats tend to be paler in color with marbled or blotched markings, while those in wetter habitats are deeper green, hence the usage of the term "ecotype" by Malhotra et al.. The same patterns are also seen in the highly variable A. marmoratus on Guadeloupe, a neighboring island group that has a range of habitats comparable to Dominica..
Ecotype descriptions
The north Caribbean ecotype (of which extremely divergent individuals were formerly classified as A. o. cabritensis) is found in the most arid part of Dominica, in low, scrub-like woodland on the northwest, Caribbean coast. It can have the most complex markings of any population, with bold, light-colored spots that run together to form irregular stripes or marbling. Males commonly have a series of prominent, lateral black splotches. Its ground color is predominantly gray or pale yellow brown, sometimes with a darker, occasionally reddish head region.
The south Caribbean ecotype (A. o. oculatus) is found on the south and southwest coast, which does not differ significantly from the north. It is the smallest in size and the palest in color and markings. It has a light tan to yellow ground color, with varying white spots that are typically indistinct. Lateral dark splotches are inconspicuous or absent. This ecotype is threatened by an invasive species (see Conservation).
The montane ecotype (A. o. montanus) is found in high elevation rain forest located in central Dominica. It has a deep green ground color, which matches the moss-covered tree trunks on which they are mostly found.. They have small, bluish-white secondary spots, and occasional lateral, black-ringed splotches on males like those found in the north Caribbean ecotype. The largest sizes are attained among this population.
The Atlantic ecotype (A. o. winstoni) is found along most of the Atlantic (east) coast of Dominica, which is wetter than the west coast. It is intermediate in size, and has a typically orange to chocolate brown ground color, with small, scattered white spots, like the montane type.
Distribution and habitat The Dominican anole is restricted to the island of Dominica, one of the few islands in the Lesser Antilles to have retained its original reptile and amphibian fauna over the last 200 years.. It is one of two lizard species endemic to Dominica, the other being the Dominican ground lizard.; ; . It is the only native anole species on Dominica.. It is present in all habitats and areas of the island up to around 900 m elevation and is generally abundant, though it is tending towards extirpation from the southwestern coastal region due to an invasive anole species (see Conservation).. The coastal woodlands of Dominica have been particularly noted as unusually favorable for reptiles, with a biomass among the highest recorded for terrestrial reptile populations; Dominican anoles have been estimated to occur in that environment at a mean density of 2148 per hectare..
Ecology
Dominican anoles are semi-arboreal, and mainly forage on the ground for food.; ; . Its diet mainly consists of insects, but varies by habitat and season based on the available food, and with the size of the individual.; It may also eat fruit and even small vertebrates.. In xeric woodland habitats on Dominica's Caribbean coast, it mainly feeds on tiny ants, termites, springtails and barklice.. Montane populations, which reach larger sizes, rely more on larger prey such as Oligochaeta (earthworms) and Orthoptera (crickets and grasshoppers), although smaller adults and juveniles in rainforest environments will also mainly feed on ants.;
The main predators of Dominican anoles are Alsophis antillensis, a species of "racer" snake, and birds including the mangrove cuckoo, thrashers, and kingbirds, all of which are mainly found in coastal regions.; .
Behavior