Dactyloidae are a family of lizards commonly known as anoles (singular anole ) and native to warmer parts of the Americas, ranging from southeastern United States to Paraguay. Instead of treating it as a family, some authorities prefer to treat it as a subfamily, Dactyloinae, of the family Iguanidae. In the past they were included in the family Polychrotidae together with Polychrus (bush anoles), but the latter genus is not closely related to the true anoles.
Anoles are small to fairly large lizards, typically green or brownish, but their color varies depending on species and many can also change it. In most species at least the male has a dewlap, an often brightly colored flap of skin that extends from the throat and is used in displays. but they are only very distantly related, anoles being part of Iguania.
Anoles are active during the day and feed mostly on small animals such as insects, but some will also take fruits, flowers, and nectar. Almost all species are fiercely territorial. After mating, the female lays an egg (occasionally two); in many species she may do so every few days or weeks. The egg is typically placed on the ground, but in some species it is placed at higher levels.
Anoles are widely studied in fields such as ecology, behavior, and evolution, and some species are commonly kept in captivity as pets. Anoles can function as a biological pest control by eating insects that may harm humans or plants, but represent a serious risk to small native animals and ecosystems if introduced to regions outside their home range.
Distribution and habitat
thumb|left|Cuba is home to [[List of amphibians and reptiles of Cuba#Lizards|more than 60 anole species (second only to Colombia), most found nowhere else, like this West Cuban anole]]
thumb|left|Like all Lesser Antillean anoles, [[Leach's anole has a very small range]]
Anoles are a very diverse and plentiful group of lizards. They are native to tropical and subtropical South America, Central America, Mexico, the offshore East Pacific Cocos, Gorgona and Malpelo Islands, the West Indies and southeastern United States. Mexico (more than 50), Central America, Colombia (more than 75), and Ecuador (at least 40). Contiguous United States (1 native species), However, the Lesser Antilles are relatively rich compared to their very small land area and their species are all highly localized endemics, each only found on one or a few diminutive islands.
thumb|left|[[Puerto Rican bush anole, one of sixteen anole species from Puerto Rico and the Virgin Islands]]
The only species native to the contiguous United States is the Carolina (or green) anole, which ranges as far west as central Texas, and north to Oklahoma, Tennessee and Virginia. Its northern limit is likely related to cold winter temperatures. Several anole species have been introduced to the contiguous US, mostly Florida, but also other Gulf Coast states and California. The most prevalent of these introductions is the brown anole. In contrast to the contiguous United States, Puerto Rico and the Virgin Islands are home to 16 native species, all endemic.) to the coast, and rainforest to desert scrub. Some species live close to humans and may use fences or walls of building as perches, even inhabiting gardens or trees along roads in large cities like Miami. They are often, especially in the Caribbean, grouped into six ecomorphs—crown giant, trunk crown, trunk, trunk ground, twig, and grass bush—that inhabit specific niches. Other less widely used groups are ground, ground bush, twig giant, saxicolous, and riparian (alternatively semi-aquatic). However, the species within each ecomorph group are not entirely alike and there are variations in the details of their niches, including both widespread generalists and more restricted specialists. The niche differentiation allows several anoles to inhabit the same locality,
Appearance and behavior
thumb|upright|A male [[Allison's anole (female all green) showing the long tail and climbing ability typical of anoles]]
Anoles vary in size. Males generally reach a larger size than females, but in a few species it is the other way around. and between in total length, including the tail. There are several large species that are more than in snout-to-vent length. Males of the largest, the knight anole, There are both robust and gracile species, and the head shape varies from relatively broad to elongate.
The tail of anoles varies, but mostly it is longer than the snout-to-vent length. Depending on exact species it can range from slightly shorter to about three times the snout-to-vent. The Caribbean twig ecomorph anoles, proboscis anole and "Phenacosaurus" anoles have a prehensile tail. Semi-aquatic anoles tend to have relatively tall, vertically flattened tails that aid in swimming, and their skin has certain microstructures that make it hydrophobic, resulting in a thin film of air on the skin surface when submerged and preventing water from staying on when exiting the water.
Underneath an anole's toes are pads that have several to a dozen flaps of skin (adhesive lamellae) going horizontally and covered in microscopic hairlike protrusions (setae) that allow them to cling to many different surfaces, similar to but not quite as efficient as a gecko. The extent of these structures and clinging ability varies, being more developed in anole species that live high in the tree canopy than ones living at lower levels. In one extreme are anoles that easily can run up windows. In the opposite end of the spectrum is the bulky anole of arid coastal Venezuela and adjacent Colombia, which is the only species completely lacking the specialized toe pad structures. The relative length of the limbs vary, mainly between different species, but to some extent also between different populations of a single species. This depends on things like the preferred perch size and whether there are ground-living predators in a habitat.
Despite having relatively small eyes, their primary sense is sight, which is excellent and in color. Their pupils are round or nearly round. The Guantanamo anole and Cuban cave anole have a transparent "window" in their lower eyelid, allowing them to see even with closed eyes, but why they have this adaption is unclear. Anoles have a good directional hearing, which is able to detect frequencies between 1000 and 7000 Hz and relatively low intensity sounds like the click of a camera.
Anoles are diurnal—active during the daytime—but can also be active during bright moonlit nights and may forage near artificial lights. Many species frequently bask in the sun to increase their temperature, but others are shade-living and do not. The majority can change their color depending on things like emotions (for example, aggression or stress), activity level, levels of light and as a social signal (for example, displaying dominance), but evidence showing that they do it in response to the color of the background (camouflage) is lacking. Whether they do it in response to temperature (thermoregulation) is less clear, with studies supporting it and contradicting it. The extent and variations of this color changing ability differ widely throughout the individual species. For example, the Carolina (or green) anole can change its color from a bright, leafy green to a dull brown color, while the brown anole can only change its shade, ranging from pale gray-brown to very dark brown. The colors are the result of their skin pigment cells, the chromatophores, of which they have three main types, but the change occurs only in the melanophores. When triggered by melanophore-stimulating hormone and other hormones, the melanosomes of the melanophores partially cover the other skin pigment cells, giving the anole a darker or browner color. and certain anoles that generally are green during the day changing to brown when sleeping at night.
Disregarding color change, minor individual variations in the basic color and pattern, mostly related to sex or age, are common. In some anole species this variation is more pronounced and not only related to sex and age. An example of this is the basic color of the Cayman blue-throated anole, which varies geographically, roughly matching the main habitat at a location. In others it occurs at the same location. This includes the extensive individual variations in the Guadeloupean anole, which however also shows some geographic variations, but possibly not consistent enough (due in part to clines) to make the typically recognized subspecies valid. In the Puerto Rican giant anole, a species only able to perform minor color changes (essentially lightness/darkness), juveniles are gray-brown and adults typically green, but an uncommon morph maintains a gray-brown color into adulthood.
Dewlap
Most—but not all—anole species have dewlaps, made of erectile cartilage (modified from the hyoid) and covered in skin, that extend from their throat areas. When not in use and closed it lies inconspicuously along the throat and chest. The size, shape, color and pattern of the dewlap vary extensively depending on species, and often it differs between the sexes, being smaller (in some absent) or less colorful in females. In a few species, including the Carolina, bark, Cochran's gianthead and slender anoles, it varies geographically in color depending on subspecies or morph. Very locally, distinct morphs of a single species that differ in dewlap colors (not just differences between sexes) may occur together. In some species even juveniles have a dewlap. The West Cuban and Cuban stream anoles are the only where both sexes lack a dewlap, but it is reduced and diminutive in about a dozen other species.
The dewlap serves as a signal for attracting partners, territoriality, deterring predators and communicating condition. When several anoles live together the species almost always differ in their dewlap, indicating that it plays a role in species recognition. Another example is the red-fanned stout and large-headed anoles, which are sister species that overlap in range and are very similar except for their dewlap color. They are highly aggressive to individuals of their own species, but not the other. When one species has its dewlap color modified to resemble the other, only a relatively minor or no increase in aggression occurs, indicating that they still can separate each other.
Several other Iguania genera, Draco, Otocryptis, Polychrus, Sarada and Sitana, have evolved relatively large, movable dewlaps independently of the anoles.
Sexual dimorphism
thumb|left|The nose differs between the sexes in the unusual [[proboscis anole (male with proboscis)]]
In some anoles the sexes are very similar and difficult to separate under normal viewing conditions, but most species exhibit clear sexual dimorphism, which allows one to fairly easily discern between adult males and females. In a few species the female is slightly larger than the male, but in others the sexes are about the same size. However, in most the males are larger, in some more than three times the mass of females. Males of some species have proportionally far longer heads than females, but in others it is nearly alike. The crest along the nape, back and/or tail is larger in the males. In species with tall crests this difference can be obvious, but in small-crested species it is often inconspicuous and easily overlooked, especially when not raised. The dewlap is often larger in males; in some species only the male has a dewlap. A less obvious difference between anole sexes is the enlarged post-cloacal scales in males.
Territoriality and breeding
thumb|400px|[[Puerto Rican crested anole exhibiting push-up behavior]]
thumb|Two male [[Carolina anoles fighting over territory at the top of a fence post]]
Almost all anole species are highly territorial, at least the males, but a few exceptions do exist, including the rock-living Agassiz's and Taylor's anoles where males do not defend a territory, and the grass anole where dominant males accept subordinant non-territorial males within their territory. Territorial anoles will fan their dewlap, bob their head, perform "push-ups", raise their crest and do a wide range of other behaviors to scare away potential competitors. If this does not scare off the intruder, a fight proceeds in which the two anoles attempt to bite each other. During fights some species of anoles are known to vocalize. In addition to the behaviors indicating dominance, anoles may move their head up and down in a head-nod display (not to be confused with the head-bob display where entire frontal part of body is moved through "push-ups"), which is a submissive sign. Females maintain a feeding territory. Males maintain a larger breeding territory, which overlaps with the feeding territory of one or several females. Generally being highly solitary animals, anoles will only infrequently congregate, but in colder regions individuals may rest adjacent to each other in groups during the winter.
In addition to differences in the appearance of the dewlap, the frequency of the dewlap opening/closing and the frequency and amplitude of the head bobbing differ between species, allowing them to separate each other. Territoriality is typically aimed at other individuals of the same species, but in a few cases it is also directed towards other anoles, as can be seen between the crested and Cook's anoles. Unlike most anoles with widely overlapping ranges, these two inhabit very similar niches and directly compete for resources.
thumb|left|Mating [[knight anoles. The male has turned dark from the normal green color. The whitish-gray patches are old skin that is in the process of being shed]]
The breeding period varies. In species or populations living in highly seasonal regions it is generally relatively short, typically during the wet season. It is prolonged, often even year-round, in species or populations living in regions with less distinct seasons. In some species where it is year-round the egg production is however higher during the rainy season than the dry season, Males attract and court females by performing a range of behaviors, often mirroring those used to scare away competitors, including extending their dewlap and bobbing their heads. fertilizing the egg inside the oviduct. The female may mate with multiple males, but is also able to store sperm inside her body for fertilization of eggs several months after mating. A female anole produces an egg in each ovary, meaning that when one is maturing in one of her follicles the yolk of another is forming in the other. Among these is the unusual Cuban cave anole where as many as 25 eggs may be glued together in a small cavity on the side of a cave wall. Although typically only laying a single egg per time (clutch), females of many anole species can lay an egg every five days to four weeks. Several species will also eat small vertebrates such as mice, small birds (including nestlings), lizards (including other anole species and Cannibalism of their own) and frogs. The slow-moving Cuban false chameleon anoles ("Chamaeleolis") are specialized snail-eaters, and a few semi-aquatic species like the Cuban stream anole may catch prey in water such as shrimp and small fish. Many will chase down or sneak up to a potential prey item, while others are sit-and-wait predators that pounce on prey when it gets close to the anole. Unusually, the Cuban false chameleon anoles have enlarged and blunt, molar-like teeth in the rear part of their jaw, allowing them to crush the shells of their snail prey. and overall they are best described as omnivorous. Some fruit-eating species, like the knight anole, may function as seed dispersers. although some species are less susceptible to water loss than others and are able to live in relatively arid places.
Predator avoidance and deterrence
thumb|left|The [[Anolis heterodermus|flat Andes anole avoids detection by moving slowly and it will often coordinate its movements with the wind]]
A wide range of animals will eat anoles, such as large spiders, centipedes, predatory katydids, snakes, large frogs, lizards, birds, monkeys, bats and carnivoran mammals. At least in part of their range, snakes may be the most significant predator of anoles. Some reptile-eating snakes have a specialized venom that has little effect on humans, but it rapidly kills an anole. On some Caribbean Islands anoles make up as much as 40–75% of the diet of American kestrels.
Anoles mainly detect potential enemies by sight, but their hearing range also closely matches the typical vocal range of birds. If hearing a predatory bird, like a kestrel or hawk, they increase their vigilance. When hearing a non-predatory bird little or no change happens. Some anole species will show their fitness by displaying their dewlap when encountering a predator; the greater the endurance of the anole, the greater the display. Conversely, when suddenly forced to share their habitat with an efficient anole predator like the northern curly-tailed lizard (for example, if it is introduced to a place where formerly not present), the anoles may decrease the amplitude of their head bobbing, making them less conspicuous, and may become slower to emerge from hiding (less willing to take a risk) after having been scared by a predator. Slow-moving anoles, like the twig ecomorphs of the Caribbean and many Dactyloa species of mainland Central and South America, are generally cryptically colored and often coordinate their movements with the wind, resembling the surrounding vegetation. However, the anoles lack the specialized toe fringes that helps basilisks when doing this. About two dozen anoles, including almost all members of the latifrons species group, all in the chamaeleonidae species group and the La Palma anole, do not have the ability to autotomize the tail.
If caught or cornered, anoles will bite in self-defense. This can be relatively effective against some predators. When fighting back and biting, sometimes for as much as 20 minutes, Puerto Rican crested anoles escape from more than of all attacks by Puerto Rican racer snakes. Some species of anoles will vocalize (typically growls, chirps or squeals) when caught. Especially the widespread convergent evolution seen in anoles living in the Greater Antilles has attracted the attention of scientists, and resulted in comparisons with the Darwin's finches of the Galápagos Islands, lemurs of Madagascar and cichlid fish in the African Great Lakes.
Ecomorphs and origin
On each major Greater Antillean Island (Cuba, Hispaniola, Puerto Rico and Jamaica), there are anole species that have adapted to specific niches and are referred to as ecomorphs: crown giant, trunk crown, trunk, trunk ground, twig and grass bush (a few additional, less widely used ecomorphs also exist). However, even within the Greater Antilles there are differences depending on island size and the amount of available habitats. The largest, Cuba and Hispaniola, have all six primary ecomorphs, while the smaller Puerto Rico and Jamaica have five and four respectively. Otherwise there are few known fossils, but early phylogenetic and immunological studies indicate that anoles originated 40–66 million years ago, first inhabitant Central or South America, and then came to the Caribbean (initially likely Cuba or Hispaniola). A more recent phylogenetic study, published in 2012, indicated that anoles originated in South America and diverged from other reptiles far earlier, about 95 million years ago.