New York (AFP) – With fewer predators in their habitat, some male chameleons appear to be developing an even more impressive game of color. This is what the researchers write in the journal Science Advances.
They observed the three-horned chameleon (Trioceros jacksonii) on the island of Oahu in Hawaii. It was introduced into the pet trade from Kenya in 1972 and then spread into the wild without being particularly threatened by predators.
Scientists from Sydney, Canberra and Melbourne, Australia, and from the now Hawaiian island of Honolulu have compared chameleons from Oahu to species from Kenya. To do this, they encounter males with other males, as predators such as birds and snakes, and observe them during courtship. Oahu chameleons showed more vivid colors when courting and competing with other males, and were less camouflaged in the presence of predators.
Rapid evolutionary progress?
Study conclusion: “The color display of a male chameleon had higher illumination contrast with the local background than that of a Kenyan chameleon.” One effect: more interest from potential sexual partners.
Because Oahu is poor in natural predators, three-horned chameleons are “less camouflaged than Kenyan chameleons when threatened by both predatory birds and snakes,” the study said. According to the researchers, these changes within only 50 years of their introduction could indicate rapid evolutionary progress and rapid adaptation.
However, the authors also emphasize that the differences could also theoretically be due to the so-called founder effect. This would be the case if the animals imported into Hawaii were already genetically different from the indigenous people in Kenya, for example because special animals were selected for trade. However, this seems unlikely to researchers because the differences between the Hawaiian and Kenyan chameleons indicate an actual adaptation to the new environment.
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