Turtles probably aren’t really closer to birds than to lizards and snakes, like RNA studies reported.
From Nature:
Tiny molecules that seemed to provide a powerful way to construct the tree of life may not have such a strong capability after all. A team of scientists has exposed1 flaws in a previously celebrated method that uses molecules called microRNAs to deduce evolutionary relationships between animals.
As well as casting doubt over some specific results published in the past few years — for example, that turtles are more closely related to lizards than to birds and alligators2 — the latest findings pour cold water on what seemed like a hot approach to solving some big mysteries in evolutionary biology.
…
The suggestion surprised researchers, including Bob Thomson, a young evolutionary biologist at the University of Hawaii at Manoa who was also analysing turtle evolution. His own evolutionary trees, built by comparing genetic sequences, offered a different outcome. “At the time, I had the impression that microRNAs were these silver bullets to solve sexy problems, so my thought was that something was wrong with my data,” he recalls.
Thomson and his colleagues re-ran the same analysis that Peterson’s team had used. This produced the same evolutionary tree — but Thomson’s team noticed something strange. The relationships among the animals suggested that a relatively large number of microRNAs had been lost over time. To Thomson, this result seemed to violate one of the main justifications for using microRNAs to build evolutionary trees in the first place: that it is almost always conserved across generations.
In short, we still don’t know.
See also: Turtles closer to BIRDS and crocodilians than to lizards and snakes?
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