Green Anole

Appearance: Anolis carolinensis is a beautiful green lizard, growing to approximately 8 inches in length, including the tail. Males are larger than females and have proportionally larger heads. The dewlap is usually pink (but can also be grayish or greenish), and is much larger in males than in females. Green anoles can undergo dramatic color changes, from bright green to dull olive, brown, and even yellowish. For this reason, many people in Florida call them “chameleons,” although the green anole’s color-changing ability is modest compared to the true chameleons (Chamaeleonidae) of Africa and Madagascar. 

Ecology and Habitat: The green anole’s body shape is that of a trunk-crown ecomorph. But with no other native anoles sharing its range in the southeastern U.S., it historically ranged from the ground to the treetops, making it more of a habitat generalist than Greater Antillean trunk-crown anoles. Today, it shares much of its range with the brown or festive anole (A. sagrei), a Cuban species introduced to Florida around the turn of the 20th century. Many observers believe that the brown anole is driving a decline in green anole populations. This may be true in some places, but another possibility is that green anoles spend more time in the trees where they coexist with brown anoles. In fact, in areas where these two species coexist, the green anole is usually seen on higher perches than the brown anole (which, as a trunk-ground ecomorph, is typically found within a couple of meters of the ground).

Green anoles are active foragers, moving around trees and shrubs in search of prey. They primarily eat insects and spiders, but will also prey on small vertebrates, consume fruit, and even drink nectar from flowers.

Geographic Range and Biogeography: Anolis carolinensis lives throughout the southeastern U.S., from Florida to North Carolina on the Atlantic coast, and west along the Gulf coast through Texas, all the way to the Rio Grande.

Its closest relative is the Cuban trunk-crown species, A. porcatus. Genetic analyses show that the green anole is probably descended from A. porcatus populations from western Cuba, which probably dispersed over water to Florida. The extent of genetic differences between A. porcatus and A. carolinensis suggest that these two species have evolved independently for at least 6 million years, which means that humans played no role in the original colonization of North America by the ancestors of today’s A. carolinensis.

Finally, the green anole itself has become established in many places outside its native range, probably because of its popularity in the pet trade. Today, you can find A. carolinensis in the Pacific (Hawaii, Guam, Palau, and other islands), the Caribbean (Grand Bahama, Anguilla, Grand Cayman), and in southern Japan.

Research Highlights

Anolis carolinensis is a very well-studied species. In a charming 1876 paper titled “The Florida Chameleon,” the Rev. S. Lockwood recounts detailed observations of his pet green anole, a lizard he called “Nolie,” and concludes that the green anole “…is everything that is commendable; clean, inoffensive, pretty, and wonderfully entertaining; provoking harmless mirth, and stirring up in the thinker the profoundest depths of his philosophy.”

Since the late 19th century, biologists have learned a great deal about the green anole, and it has become a model organism for studying many aspects of reptile biology, including the regulation of behavior and reproduction by hormones, social behavior and communication, and the biology of regeneration (because, like most anoles, the green anole can lose and re-grow its tail). In 2011, because of its key role in many subdisciplines of biology, the green anole became the first reptile species to have its entire genome sequenced.

A few recent studies are particularly fascinating. Recall that green anoles coexist with invasive brown anoles (A. sagrei) in parts of their range (see Ecology and Habitat above). In a 2014 study, Yoel Stuart, Todd Campbell, and colleagues studied these two species in Florida by introducing brown anoles to a subset of small, manmade islands that were already inhabited by green anoles. They found that not only did green anoles move to higher perches on the islands they shared with brown anoles, but that over a period of 15 years, the green anoles evolved larger toe pads and more toe pad lamellae (both traits associated with better climbing ability). This may be the best evidence yet that competition between anole species can drive their evolutionary diversification.

Green anoles were in the news again after a 2017 study by Shane Campbell-Staton and colleagues. Studying green anoles in Texas, they measured the lizards’ cold tolerance before and after the winter of 2013-2014, when Texas experienced an abnormally cold “polar vortex” event. Their results show that the extreme cold caused natural selection on the anoles, with southerly populations exhibiting greater cold tolerance after the 2014 polar vortex, on average, than before. Campbell-Staton also used cutting-edge genetic techniques to identify some of the genes that may be involved in cold tolerance.

Species account author: Neil Losin

For more information:
Anolis carolinensis at Animal Diversity Web
Anolis carolinensis at Encyclopedia of Life

Crested Anole

Appearance: The crested anole, Anolis cristatellus, is a medium sized lizard (50-75mm SVL in adult males) with a stocky body and relatively long limbs. It is light brown in color and both males and females have varying patterns of dark brown on their backs including mottled coloration, hourglass patterns, and longitudinal stripes. As the common name implies, many individuals have a large tail crest (different from the nuchal crest that can be erected in many species), although there is substantial regional variation in this trait and many individuals have no tail fan at all. Dewlap color is typically two-toned with a yellow center and a thick orange outer edge, although some populations have a more monotone yellow-orange dewlap. Females are smaller than males (30-45mm SVL adults) and have relatively small dewlaps. Post-anal scales are not easily visible in this species, sometimes making it difficult to distinguish females from juvenile males. 

Within the native range, this species may be confused with Anolis gundlachi and Anolis cooki. Anolis gundlachi can be distinguished from A. cristatellus by the yellow-tipped chin, blue eye, and solid yellow dewlap, but is otherwise similar in size and appearance. Anolis cooki is more difficult to distinguish from A. cristatellus, but the two only co-occur in the dry forests of southern Puerto Rico. In their non-native range in Florida, this species may be confused with Anolis sagrei, which is slightly smaller in size and has a dewlap that is red-orange in the center with a thin band of yellow on the edge. 

Ecology and Habitat: The crested anole is a trunk-ground ecomorph. It typically perches relatively low to the ground (around 2m high or lower) on broad diameter trees. It is often observed in foraging position on tree trunks with head downward as it sits and waits for insect prey to pass by on the ground. It typically eats insects and spiders, but is also known to consume fruits and to prey on small vertebrates, including anoles of their own and other species. This species is rarely seen on the ground except for when moving between perches or catching prey. Like other trunk-ground ecomorphs, A. cristatellus, has relatively long limbs and a stocky build ideal for quickly navigating both arboreal and ground habitat. Anolis cristatellus is commonly found at lower elevations in warm forest habitats and is often restricted to edge or open, disturbed forest habitat at cooler, high elevations. This species is the most common and abundant anole in urban areas in Puerto Rico.  

Geographic Range and Biogeography: Anolis cristatellus is endemic to the Puerto Rican bank (Puerto Rico and the Virgin Islands). Its closest relative is A. desechensis, which is found only on the island of Desecheo off the west coast of Puerto Rico. It is also closely related to A. scriptus (found in the Turks and Caicos), A. cooki (found in dry forests in the southwest of Puerto Rico), and A. monensis (found on the island of Mona off the coast of Puerto Rico). Genetic analyses indicate that the ancestor to A. cristatellus (and 12 other Puerto Rican species, which make up the “cristatellus” group) likely colonized Puerto Rico from Hispaniola at least 40 MYA. More recently, A. cristatellus has established in several places outside of its native range, facilitated largely by sale of tropical plants. In particular, it is established in Miami (Florida), Dominica, Costa Rica, Mexico (Yucatan), Trinidad, Saint Martin, and the Dominican Republic. 

Research Highlights:

 Anolis cristatellus is a great study species for answering so many different questions! As the most wide-ranging Puerto Rican species, it is perfect for comparative studies. Researchers have found no end to the questions they can answer by examining variation within A. cristatellus in different environments and between A. cristatellus and other Puerto Rican species.   

For example, with populations in cold, wet, montane habitats to hot, dry, coastal habitats and everything in between, A. cristatellus is perfect for comparing how populations vary in physiological tolerances. Because of this, A. cristatellus has played a major role in our understanding of thermal preferences and tolerances. This follows largely from Ray Huey, Paul Hertz, and colleagues’ foundational work in the 1970’s-80’s, which compared thermal preferences and tolerances of A. cristatellus and established that A. cristatellus is a thermoconformer in some habitats and a thermoregulator in others. Recent work on thermal tolerance in A. cristatellus has made great strides in our understanding of thermal physiology of anoles. For example, researchers have found that thermal tolerance in A. cristatellus can rapidly shift in new environments. Manuel Leal and Alex Gunderson found that in Miami A. cristatellus tolerate much cooler temperatures than populations in Puerto Rico, and Shane Campbell-Staton and Kristin Winchell found that urban populations in Puerto Rico tolerate much hotter temperatures than nearby forest populations.  

In addition, because they are widespread in disturbed environments in their native and non-native range, they provide a great opportunity to study rapid contemporary adaptation in response to environmental change. For example, Luisa Otero has found that reproductive patterns vary with habitat disturbance over small geographical scales and Joshua Hall found that embryo survival and development is impacted by urban thermal spikes. Urban environments in particular have received substantial attention, with researchers in Miami examining invasion dynamics and artificial night light use, and researchers in Puerto Rico finding shifts in habitat use, morphology, and performance in urban environments.  

Species account author: Kristin Winchell 

For more information:  

Reptile Database: http://reptile-database.reptarium.cz/species?genus=Anolis&species=cristatellus 

Animal Diversity Web: https://animaldiversity.org/accounts/Anolis_cristatellus/ 

Invasive Species Compendium: https://www.cabi.org/isc/datasheet/93810 

Bark Anole

Appearance: Anolis distichus, the bark anole, is a medium sized anole with a body color that varies from gray, to brown, to green – depending on the population. Body coloration is similar in both sexes but females can be distinguished from males by their lack of a dewlap, smaller adult size, and a relatively flatter head than males. Male dewlap color in this species is widely variable with populations ranging from pale white or yellow, to populations with variably sized red or orange spot in the center, to populations with entirely red or orange dewlaps. Bark anoles co-occur with a variety of species, most of which can be easily distinguished as different ecomorphs with larger heads or bodies such as Crown Giant and Trunk Ground anoles, or more slender frames such as of Trunk Crown, Grass Bush and Twig anoles. In Haiti and the Dominican Republic, the range of bark anoles overlaps with those of other closely-related trunk anole species – Anolis brevirostris, Anolis caudalis, Anolis marron, and Anolis websteri. These species all have a black spot on their neck, which is lacking in Anolis distichus.

Ecology and Habitat: Anolis distichus are trunk anoles, an ecomorph with a compact body plan – short snout and tail, with a relatively wide midsection. Trunk anoles like Anolis distichus primarily occupy the vertical surfaces of trees, usually below the canopy. They are found in a wide variety of natural habitats including xeric scrub to mesic humid forests as well as human-created habitats like buildings, parks, fruit tree groves, and residential areas. Unlike other ecomorphs that flee up trees or run to the ground when approached, bark anoles often shimmy to the opposite side of the trunk, a behavior commonly referred to as “squirrelling”. Bark anoles will eat nearly any prey that can fit in their mouth but their primary diet includes small arthropods like crickets, beetles, and even bees! Bark anoles are especially fond of ants.   

Geographic Range and Biogeography: Bark anoles are native to Hispaniola (Haiti and the Dominican Republic) and the central Bahamas. Although they were once considered native to Florida, genetic data suggests these populations are the result of multiple introductions from Hispaniola and the Bahamas some of which occurred at least 50 years ago. They are thought to be introduced to Abaco Island in the northern Bahamas, but fossil evidence of this species on Abaco puts the status of this population into question. Phylogenetic evidence finds that bark anoles arose on the northern paleo-island of Hispaniola, dispersed over-water to colonize the the Bahamas, and spread to areas of to the southern Hispaniolan paleo-island after the two paleo-islands fused to form present day Hispaniola. 

The immense variation in body and dewlap color in bark anoles has led to the description of 18 subspecies of Anolis distichus. Research currently underway seeks to understand if these subspecies are in the process of speciation or have perhaps already achieved species status. 

Research Highlights:  

Bark anoles have long been the intensive research effort with particular interest in using bark anoles to understand 1) the evolution of signals and 2) the process of speciation.  

Most anole species possess and make extensive use of their colorful dewlaps for signaling to each other as well as other species. A series of studies led by Julienne Ng has shown that dewlap color is a heritable genetic trait and is associated with signaling environment that animal occupies. Exciting research, currently underway by Winter Beckles, seeks to understand if bark anole populations shift their dewlap color in response to changes in their light environment caused by hurricanes. 

Julienne Ng has also found that some subspecies with different dewlaps interbreed freely over a wide geographic area. In contrast, other subspecies pairs are confined to a narrow hybrid zone suggesting that, for these subspecies pairs, hybridization may have negative fitness consequences and those populations may be in the process of speciation. Research I performed as part of my dissertation also found that transitions in dewlap color are associated with diversification events suggesting dewlap divergence may play in role in driving or maintaining speciation events.  We also found evidence found that there are more distinct lineages that previously recognized within the Anolis distichus group and one subspecies in particular – Anolis distichus dominicensis is actually three separate lineages. Work I performed with undergraduate researcher (now Yale PhD student) Daniel MacGuigan used multispecies coalescent methods to assess if Anolis distichus represents a single species or multiple species. We found support for at least seven distinct species in the group, but at present we have not updated the taxonomy because the boundaries between these species remain unclear, particularly for the separate lineages of A. distichus dominicensis.  

Species account author: Anthony J. Geneva 

For more information:  

Encyclopedia of Life 

Reptile Database 

Brown Anole

Appearance: Anolis sagrei may not be the most colorful or strikingly patterned anole, but owing to its widespread distribution and high abundance it may the anole most familiar to you. Adults commonly grow to 7-8 inches from head to tail with females being a few inches smaller than males. Their body color ranges from light tan to gray to dark brown, almost black. Unlike green anoles that can turn brown, these guys are never green! Males have red-orange dewlaps, sometimes with a yellow border or blotches. Females often have a pattern with diamonds, bars, or a stripe running down their back. When in south Florida don’t confuse brown anoles with crested anoles (Anolis cristatellus). Crested anole females only have a cream-colored stripe on their backs, and brown anoles do not have a light ring around the eye or a light stripe above their front limb. Brown anoles often have two dark bars above their eyes.

Ecology and Habitat: The brown anole is a trunk-ground habitat specialist or ecomorph. They are often found on the ground or perching low on tree trunks (up to 1.5 m high). Brown anoles have relatively long limbs for their body size, which allows them to run fast on the ground and tree trunks that they typically occupy. Brown anoles are usually sit-and-wait foragers, keying in on the movement of prey to jump from their perch and attack. Their diet consists of a wide variety of arthropods including most any spiders and insects they can fit in mouths. They will occasionally eat other invertebrates and small vertebrates including their own hatchlings. Brown anoles primarily occupy disturbed and edge habitats in both natural and human-modified landscapes. Their abundances suggest they are just as at home in the city as in natural areas. Like tourists at the beach, these guys love the sun – they are often active during the hottest parts of the day. All anole species display, but brown anoles are the champions – they are often seen fanning their brightly colored dewlaps, and doing head-bobs and push-ups with the intensity and stamina of an Olympic athlete. 

Geographic Range and Biogeography: The native range of the brown anole includes the Bahamas, Belize, Cuba, Cayman Brac, Little Cayman, Swan Island and the Gulf of Mexico/Caribbean coast of Mexico. Its evolutionary origin as part of the 15-species sagrei group is Cuba with multiple colonization events to Caribbean islands east and west of Cuba to round out its native range. One of the best natural colonizers of all anoles, brown anoles are also the undisputed champion of recent human-mediated introductions. Non-native populations are well established around the world including the southeastern United States (e.g. Alabama, Florida, Georgia, Texas), Atlantic islands (e.g. Ascension, Bermuda), Caribbean islands (e.g. Grand Cayman, Grenada, Jamaica, St. Vincent), and Pacific islands (e.g. Hawaii, Taiwan), among other locations with reports of new introductions every year. Genetic analyses reveal multiple origins of these introduced populations from numerous localities in Cuba as well as the Bahamas and Belize. A key discovery about these introductions is that genetic variation from these multiple native-range sources mixes within non-native populations, resulting in increased genetic variation compared to native-range populations.  

Research Highlights: 

If Anolis carolinensis (green anole) is the “lab rat” of the reptile world, then Anolis sagrei is undoubtedly the “field rat.” This species has been studied extensively in the field from populations on small islands in the Bahamas to the heart of the city in Miami. A well-studied natural history, high local abundance, and the ability to tag individuals for unique identification make this species ideal for field studies of natural selection. We have learned that natural selection acts on morphological, physiological and behavioral traits of brown anoles. For example, natural selection favors longer hindlimbs in the presence of terrestrial predators (curly-tailed lizards, Leiocephalus carinatus) and higher optimal performance temperatures in warmer habitats. Other studies show adaptive responses of limbs to local vegetation after being introduced to new islands. A recent study by Oriol Lapiedra and colleagues evaluated whether natural selection acts on variation in risk-taking behavior of brown anoles when they occupy small islands with and without the ground predator Leiocephalus carinatus. Brown anoles that avoided the ground in lab trials were favored in the presence of the predator, whereas more exploratory brown anoles survived better in the absence of the predator. Moreover, selection on behavior and morphology acted independently. This experiment is among the best studies yet showing that natural selection acts on behavior.  

AA post:  https://www.anoleannals.org/2017/06/27/evolution-2017-it-doesnt-pay-to-be-risky-when-predators-are-about/ 

Brown anoles are also a key species in studies of the consequences of global environmental change, including biological invasions, climate change, and urbanization. Recent studies of non-native brown anoles in Miami by Jason Kolbe and his lab discovered that brown anoles living in the city have consistently different personalities compared to their forest counterparts – city lizards are more tolerant of humans, less aggressive, more exploratory in new environments, and bolder after simulated predator attacks. Cities also dramatically alter the ecological niche space occupied by brown anoles. Urban heat islands produce warmer microclimates that allow brown anoles to more often attain their preferred body temperatures during the summer in Miami, likely increasing their ability to persist in some areas. Brown anoles prefer to perch on broad substrates like tree trunks, and urbanization typically results in the removal of smaller trees and the addition of broad diameter artificial structures, such as light posts and utility poles. This leads brown anoles to use broader perches in urban areas despite the fact these artificial substrates are often quite smooth and lizards slip and fall when using them.  

Video:  https://www.anoleannals.org/2016/09/08/lizards-running-and-slipping-in-ultra-slo-mo/ 

For more information:  

Animal Diversity Web: https://animaldiversity.org/accounts/Norops_sagrei/ 

SREL: https://srelherp.uga.edu/lizards/anosag.htm 

The Reptile Database: http://reptile-database.reptarium.cz/species?genus=Anolis&species=sagrei