September 5, 2013
Genetic Similarities In Echolocation Discovered In Bats And Dolphins
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redOrbit Staff & Wire Reports - Your Universe Online
Convergent evolution – the evolution of similar traits in drastically different types of creatures – is widespread not just at the physical level but also at the genetic level, according to new research published in this week’s edition of the journal Nature.
As part of their study, scientists from Queen Mary University of London analyzed the genomic basis for echolocation, a complex physical trait that involves the creation, reception and auditory processing of ultrasonic pulses for tracking down prey or detecting unseen obstacles. Echolocation, which is one of the most well-known examples of convergent evolution, developed separately in different groups of bats and cetaceans such as dolphins.
In order to discover the extent to which convergent evolution of a physical feature involves the same genes, the researchers set out to conduct one of the largest genome-wide surveys of its type.
They compared the genomic sequences of 22 mammals (including the genomes of bats and dolphins) each of which independently evolved echolocation. In order to perform the analysis, they reviewed millions of letters of genetic code using a computer program developed to calculate the probability of convergent changes happening by chance.
Using a supercomputer at Queen Mary’s School of Physics and Astronomy, the study authors found genetic signatures consistent with convergence in nearly 200 different genomic regions concentrated in several “hearing genes.” They also uncovered signs of convergence among bats and bottlenose dolphins, consistent with involvement in echolocation, in multiple genes that had been previously linked to hearing or deafness.
“We had expected to find identical changes in maybe a dozen or so genes but to see nearly 200 is incredible,” first author Dr. Joe Parker of Queen Mary's School of Biological and Chemical Sciences explained in a statement. “We know natural selection is a potent driver of gene sequence evolution, but identifying so many examples where it produces nearly identical results in the genetic sequences of totally unrelated animals is astonishing.”
Dr. Georgia Tsagkogeorga, who assembled the new genome data for the study, added that they found “widespread” molecular signs of convergence in multiple genes across the genome. She said that the discovery “greatly adds to our understanding of genome evolution.”
Likewise, her colleague Dr. Stephen Rossiter, who served as the group leader of the project, said that the results could be just “the tip of the iceberg,” as future genomic research might reveal “other striking cases of convergent adaptations being driven by identical genetic changes.”