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Unrelated lizards evolved the same skills over millions of years

Unrelated lizards in very different parts of the world have learned the same skills, despite evolving separately for hundreds of millions of years, according to a new study from the University of New South Wales

The experts say their research shows that natural selection directs evolution toward the same common set of adaptive outcomes over and over again.

The study reveals that the Anolis lizards in the Caribbean and the Draco lizards in Southeast Asia communicate in the same way to defend their territories and attract mates. 

Males from both species perform elaborate dances, bobbing their heads with exaggerated movements. They also puff out their brightly colored dewlap, or throat fan, and even do some pushups.

Since the lizards occupy the same types of rainforest and grassland habitats, they also face the same communication challenges. Remarkably, they have evolved the same strategy to cope with the same selection problems, said study lead author Dr. Terry Ord of the UNSW School of Biological, Earth and Environmental Sciences.

“The surprise is that lizards in both groups have evolved remarkably similar displays for communication, but they also tailor the production of those displays according to the prevailing conditions experienced at the time of display,” explained Dr. Ord.

“That is, increasing the speed or the length of time they spend displaying the movements as the viewing conditions deteriorate.”

“Really there should be essentially innumerable ways these lizards could have adapted their displays to remain effective, and there is strong evolutionary predictions that would lead us to expect this as well.”

According to Dr. Ord, the study shows that natural selection is driving similarities between different species. Formally, this is known as convergent evolution – the independent origin of similar adaptations – he explained.

“It seemed that these types of convergent, common adaptations are outcomes that would only really occur among species that are closely-related in some capacity.”

“The reason for this is a bit complicated and it rests on the fact that adaptations build on characteristics that a species already possesses.”

“So, the longer species have evolved independently of each other, the less likely they would evolve the same adaptive solutions if they were exposed to the same change in the environment.”

What this study highlights, said Dr. Ord, is what many evolutionary ecologists have argued – that natural selection is an extremely powerful process that can override the “baggage” of past history to produce the same adaptations.

“So if arm-waving is the most effective solution to some change in the environment, then natural selection would ultimately lead to its evolution rather than a more subtle (less effective) modification to an existing vocal call.”

“Evolutionary biologists are excited about convergent evolution because it gives us multiple examples of the same adaptation evolving time and time again in very different animals.?

“So it tells us what the challenges are faced by these animals and how they have solved it in terms of evolutionary adaptation.”

Dr. Ord said the striking similarities in communication strategies under noisy conditions has evolved not only in lizards, but also among many insects, fish, frogs, birds and mammals.

“For example, increasing the volume of calls when there’s lots of acoustic background noise, or extending the length of those calls or even vibrational signals by spiders and such.”

“The fact that many other groups of animals have also evolved thesesame adaptive strategies is even more extraordinary.”

The study is published in the journal Ecology Letters.

By Chrissy Sexton, Staff Writer

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