According to European scientists reporting in the journal Nature, bottlenose dolphins and bats have a genetic resemblance due to their echolocation capability.
A depiction of the ultrasound signals emitted by a bat, and the echo from a nearby object. Image credit: Petteri Aimonen.
Echolocation is a complex physical trait that involves the production, reception and auditory processing of ultrasonic pulses for detecting unseen obstacles or tracking down prey, and has evolved separately in different groups of bats and cetaceans including dolphins.
The scientists carried out one of the largest genome-wide surveys of its type to discover the extent to which convergent evolution of a physical feature involves the same genes.
They compared genomic sequences of 22 mammals, including the genomes of bats and dolphins, which independently evolved echolocation, and found genetic signatures consistent with convergence in nearly 200 different genomic regions concentrated in several ‘hearing genes’.
To perform the analysis, the team had to sift through millions of letters of genetic code using a computer program developed to calculate the probability of convergent changes occurring by chance, so they could reliably identify ‘odd-man-out’ genes. They used a supercomputer called the GridPP High Throughput Cluster at Queen Mary’s School of Physics and Astronomy, UK, to carry out the survey.
Consistent with an involvement in echolocation, signs of convergence among bats and the bottlenose dolphin were seen in many genes previously implicated in hearing or deafness.
“We had expected to find identical changes in maybe a dozen or so genes but to see nearly 200 is incredible,” said study lead author Dr Joe Parker of Queen Mary’s School of Biological and Chemical Sciences.
“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.”
“We found that molecular signals of convergence were widespread, and were seen in many genes across the genome. It greatly adds to our understanding of genome evolution,” added co-author Dr Georgia Tsagkogeorga, also from Queen Mary’s School of Biological and Chemical Sciences.
“These results could be the tip of the iceberg. As the genomes of more species are sequenced and studied, we may well see other striking cases of convergent adaptations being driven by identical genetic changes,” said senior author Dr Stephen Rossiter of Queen Mary’s School of Biological and Chemical Sciences.
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Bibliographic information: Joe Parker et al. Genome-wide signatures of convergent evolution in echolocating mammals. Nature, published online September 04, 2013; doi: 10.1038/nature12511
