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Common blue-tongued skink (Tiliqua s. Scincoides), basking on open sandy ground. Credit: CC BY-SA 3.0
A team of researchers affiliated with Clark University, the Museum of Natural History, Yale University and the University of Massachusetts Amherst, have developed a theory to explain why skinks living in the Philippines have lost their legs over many years of evolution, and then they regained them many years later. In their article published in Proceedings of the Royal Society B, the group describes their study of the little lizard and what they learned about it.
One of the rules of thumb in evolutionary theory is that when a creature loses a complicated structure (such as its legs) for many years, its descendants are very unlikely to express them later. In this new effort, the researchers found a possible reason for an exception to the rule: Brachymeles lizards, more commonly known as skinks, which lost their legs and then regrown them.
Previous research had suggested that some of the native Philippine skinks had once lost their legs due to evolution and then, for unknown reasons, their legs returned many years later. Other skinks living nearby had also lost their legs but did not grow them. In this new effort, the researchers tried to understand why it happened with one group but not the other.
The work involved inserting captured skink specimens (both those that had re-evolved legs and those that hadn’t) through a variety of physical tasks, such as running a small racecourse. The idea was to find out what types of conditions might be best suited to leg use and which ones might be best suited to snake-like mobility.
The researchers found that legless skinks were better able to move in dry conditions – without legs, they were better at digging, for example. On the other hand, skinks with legs (and feet) were better able to move in wetter conditions. Their legs allowed them to navigate the wet ground. Researchers suggest that the legs in skinks appear during long periods of wet conditions and then disappear during long periods of drought.
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Philip J. Bergmann et al. Locomotion and paleoclimate explain the re-evolution of the quadrupedal body shape in Brachymeles lizards, Proceedings of the Royal Society B: Biological Sciences (2020). DOI: 10.1098 / rspb.2020.1994
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Quote: Why skinks that lost their legs evolved new ones (2020, November 11) recovered on November 11, 2020 from https://phys.org/news/2020-11-skinks-lost-legs-evolved.html
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