Jul 21, 2019 | Updated: 09:46 AM EDT

Sunbathing Lizards in the Caribbean Evolve Slower than Mainland Lizards

Apr 24, 2019 12:12 PM EDT

Male Dominican Anole
(Photo : Postdlf)
Male Dominican Anole extending its throat fan.

The shores of the Caribbean is home to sunbathers of different types and sizes. There are some who frequent the shores for a little splash of water, there also those who are perfectly comfortable on a widespread blanket, some with a drink in hand, and there are those who spend much of the day scurrying in and out of the shade to have their tails and their scales be treated with either a little bit of warm sunshine or a cool shadow. 

Of course, The last part pertains to anoles which are little tree lizards. 

The said trait is called behavioral "thermoregulation" as explained by Martha Muñoz of Virginia Tech and Jhan Salazar of Universidad Icesi in their study. Scientists further explained that this trait does not only affect the lizard's body temperature as previously known but also slows down the evolution of the creatures.

To further understand why slow evolution on the island is treated as a strange phenomenon, the scientists refer to the fact that islands have been recognized as hotspots for rapid evolution. This is because of the ecological opportunity presented by a change in environment. For example, when organisms are washed up on remote islands they are freed from their usual competitors and predators. As a result, the organisms would rapidly diversify. This faster evolution is also known as the "Island effect." 

However, the researchers found that there is much slower evolution on the island than on the mainland for anole lizards. This is because the island lizards move around more and are able to spend much of their day chasing either the sun or the shade, whereas the mainland lizard would spend most of their time just hiding from predators.

This means mainland lizards are able to diversify as they are frequently exposed to their predators which could be treated as "extreme situations." Island lizards on the other hand simply find a shady spot if it gets too hot or to a warm sunny spot if it gets too cold. Their thermoregulating trait buffers themselves from variation in temperatures which effectively shield them from natural selection. This would weaken their physiology and therefore slow down their physiological evolution.

Salazar explains that the results of their study show that faster evolution in islands is not a general rule.

Muñoz ads that organisms can be treated as architects of their own selective environments where evolution and behavior work simultaneously.

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