Lizards are running on the fast track of evolution

April 22nd, 2008 - 12:34 pm ICT by admin  

National Geographic

Washington, April 22 (ANI): A new research has shown that lizards are literally running on the fast track of evolution, with the prime example being Italian wall lizards introduced to a tiny island off the coast of Croatia, that evolved in 30 years in ways that would normally take millions of years to play out.

According to a report in National Geographic News, in just a few decades, the 5-inch-long (13-centimeter-long) lizards have developed a completely new gut structure, larger heads, and a harder bite.

In 1971, scientists transplanted five adult pairs of the reptiles from their original island home in Pod Kopiste to the tiny neighboring island of Pod Mrcaru, both in the south Adriatic Sea.

Genetic testing on the Pod Mrcaru lizards confirmed that the modern population of more than 5,000 Italian wall lizards are all descendants of the original ten lizards left behind in the 1970s.

According to Duncan Irschick, a study author and biology professor at the University of Massachusetts, Amherst, when the researchers went back to the island, they had no idea if the original introductions were successful.

When they found that the island swarming with lizards, the researchers were taken aback.

The new habitat once had its own healthy population of lizards, which were less aggressive than the new implants, said Irschick. The new species wiped out the indigenous lizard populations, although how it happened is unknown, he added.

According to Irschick, the transplanted lizards adapted to their new environment in ways that expedited their evolution physically.

Pod Mrcaru, for example, had an abundance of plants for the primarily insect-eating lizards to munch on. Physically, however, the lizards were not built to digest a vegetarian diet.

Researchers found that the lizards developed cecal valvesmuscles between the large and small intestinethat slowed down food digestion in fermenting chambers, which allowed their bodies to process the vegetations cellulose into volatile fatty acids.

They evolved an expanded gut to allow them to process these leaves, said Irschick, adding it was something that had not been documented before. This was a brand-new structure, he said.

Along with the ability to digest plants came the ability to bite harder, powered by a head that had grown longer and wider.

The rapid physical evolution also sparked changes in the lizards social and behavioral structure. For one, the plentiful food sources allowed for easier reproduction and a denser population.

The lizard also dropped some of its territorial defenses, the authors concluded.

Such physical transformation in just 30 lizard generations takes evolution to a whole new level, said Irschick. Thats unparalleled. Whats most important is how fast this is, he added. (ANI)

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