The green anole or Carolina anole (Anolis carolinensis) is common in pet stores where it is sometimes identified as the American chameleon because of its ability to change color from green to brown. It is important to note, though, that these lizards are not actually a type of chameleon. Green anoles are the only anole lizard native to North America, and are found primarily in the southeastern United States, with recent introductions to Hawaii, Guam, and elsewhere. They are very common throughout their distribution, typically found on the sides of buildings, on shrubs or vines, and high in trees. They periodically are also found on the ground. As their name suggests, these lizards are emerald green in color, but can change to brown. Both males and females have a pink throat fan (a.k.a. dewlap), which is used as a means for inter- and intraspecific communication. Their toes are expanded at the tips to accommodate adhesive toe pads, which aid them in climbing smooth surfaces where claws cannot be used. The reproductive season takes place during the months of April through July, when the typically territorial males become even more intensely territorial, attempting to secure exclusive access to groups of females. Female anole lizards can lay one egg each week throughout the four-month breeding cycle. The green anole has been a particularly important organism for study in the scientific community, and has been successfully used as a model system for studying neurological disorders and for studying drug delivery systems and biochemical pathways relevant to human illnesses. They have also been essential for scientific progress in understanding other aspects of physiology and behavior in animals. The Genus Anolis, which includes over 350 recognized species, also serves as a group of major interest for exploring the evolutionary diversification; of particular interest is the repeated convergent pattern of adaptive radiation on islands of the Greater Antilles, producing on each island essentially the same set of habitat specialists adapted to use different parts of the environment. As a result, in 2005, the scientific community overwhelmingly chose the green anole lizard as its first target species for reptilian genome sequencing. In recent years, populations of A. carolinensis have apparently become less common, although no data are available. This decline is correlated with massive habitat alteration and the introduction of the brown anole (Anolis sagrei) from Cuba. Anolis carolinensis is derived from A. porcatus on Cuba, which coexists with A. sagrei. One possibility is that the presence of A. sagrei in Florida has caused A. carolinensis to return to the more arboreal ecological niche occupied by A. porcatus.