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''Anolis'' is a
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
of
anole Dactyloidae are a family of lizards commonly known as anoles () 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 subfami ...
s (), iguanian lizards in the family
Dactyloidae Dactyloidae are a family of lizards commonly known as anoles () 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 subfam ...
, native to the
Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North America, North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. ...
. With more than 425 species, it represents the world's most species-rich
amniote Amniotes are a clade of tetrapod vertebrates that comprises sauropsids (including all reptiles and birds, and extinct parareptiles and non-avian dinosaurs) and synapsids (including pelycosaurs and therapsids such as mammals). They are dis ...
tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct t ...
genus, although many of these have been proposed to be moved to other genera, in which case only about 45 ''Anolis'' species remain.Abstract
/ref> Previously, it was classified under the family Polychrotidae that contained all the anoles, as well as '' Polychrus'', but recent studies place it in the Dactyloidae.


Taxonomy

This very large
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
displays considerable paraphyly, but phylogenetic analysis suggests a number of subgroups or
clades A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English te ...
. Whether these clades are best recognized as subgenera within ''Anolis'' or separate genera remains a matter of dispute. If the clades are recognized as full genera, about 45 species remain in ''Anolis'', with the remaining moved to ''Audantia'' (9 species), ''Chamaelinorops'' (7 species), ''Ctenonotus'' (more than 40 species), ''Dactyloa'' (''circa'' 95 species), ''Deiroptyx'' (almost 35 species), ''Norops'' (about 190 species), and ''Xiphosurus'' (around 15 species). Some of these can be further subdivided. For example, ''Phenacosaurus'' was often listed as a full genus in the past, but it is a subclade within ''Dactyloa'' (''Dactyloa heteroderma'' species group). Among the subgroups within ''Anolis'' are: * ''
carolinensis The ''Anolis carolinensis'' series is a proposed clade or subgroup of closely related mid-sized trunk crown anoles () within the genus ''Anolis''. It was created by Nicholson ''et al''. in 2012 and defined as containing 13 species, a few example ...
'' species group (13
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...
) * ''isolepis'' species group (three species) In 2011, the green (or Carolina) anole (''Anolis carolinensis'') became the first reptile to have its complete genome published. Closely related, recently diverged anole lizards exhibited more divergence in thermal biology than in morphology. These anole lizards are thought to have the same structural niche and have similarities in their size and shape, but they inhabit different climatic niches with was variability in temperature and openness of the environment. This suggests that thermal physiology is more associated with recently diverged anole lizards.


Ecomorphs

''Anolis'' lizards are some of the best examples of both
adaptive radiation In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic in ...
and
convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
. Populations of lizards on isolated islands diverge to occupy separate
ecological niches In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for ...
, mostly in terms of the location within the vegetation where they forage (such as in the crown of trees vs. the trunk vs. underlying shrubs). These divergences in
habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
are accompanied by morphological changes primarily related to moving on the substrate diameter they most frequently encounter, with twig ecomorphs having short limbs, while trunk ecomorphs have long limbs. In addition, these patterns repeat on numerous islands, with animals in similar habitats converging on similar body forms repeatedly. This demonstrates adaptive radiation can actually be predictable based on habitat encountered, and experimental introductions onto formerly lizard-free islands have proven ''Anolis'' evolution can be predicted. After appearing on each of the four Greater Antillean Islands about 50 million years ago, ''Anolis'' lizards spread on each island to occupy niches in the island's trees. Some living in the tree canopy area, others low on the tree trunk near the ground; others in the mid-trunk area, others on twigs. Each new species developed its own distinct body type, called an ecomorph, adapted to the tree niche where it lived. Together, the different species occupied their various niches in the trees as a "
community A community is a social unit (a group of living things) with commonality such as place, norms, religion, values, customs, or identity. Communities may share a sense of place situated in a given geographical area (e.g. a country, village, t ...
". A study of lizard fossils trapped in amber shows that the lizard communities have existed for about 20 million years or more. Four modern ecomorph body types, trunk-crown, trunk-ground, trunk, and twig, are represented in the amber fossils study. Close comparison of the lizard fossils with their descendants alive today in the Caribbean shows the lizards have changed little in the millions of years.


Behavior

As ectotherms, ''Anolis'' lizards must regulate their body temperature partly through behavioral changes and bask in the sunlight to gain enough heat to become fully active, but lizards cannot behaviorally warm themselves at night when temperatures drop. Because of this, cold tolerance evolves faster than heat tolerance in these lizards. On the island of Hispanola, both high-altitude and low-altitude lizard populations exist, and the thermal conditions at high and low elevations differ significantly. High-altitude lizards have shifted their ecological niche to boulder environments, where warming themselves is easier, and they show changes in the shape of limbs and skull that make them better adapted to these environments.


Species

The ''Anolis'' lizards that are less susceptible to predation are those with a dewlap in which both the scales and the exposed skin areas between them match the usual pale gray or whitish of the rest of the ventral surface.


References


Further reading

*


External links


Anole Annals
a blog written and edited by scientists who study ''Anolis'' lizards
''Anolis''
The Reptile Database
Adapting Anolis
short film on adaptations of Cuba's ''Anolis'' lizards {{Authority control A Lizard genera Taxa named by François Marie Daudin Fauna of the Dominican Republic