If convergence is common in this system, it will advance our knowledge of echolocation, for example by identifying a number of genes probably involved in this system. ![]() To confirm our finding, we want to search for convergent sequences across entire genomes, looking for genes that show convergence between the groups of echolocating bats, between bats that share similar echolocation calls, and also between bats and whales. Methods to detect convergence in DNA or protein sequences are also relatively new. This may be partly because few scientists have been looking for this kind of convergence, and there has been no systematic attempt to investigate how common it might be. Our evidence suggests that molecular convergence may be far more common than currently suspected. The identification of convergent molecular evolution in a number of different genes associated with a particular trait is, to our knowledge, unprecedented. Therefore, such cases are unlikely to arise by chance. Any finding of convergence of this kind is surprising, as the number of possible sequences for any gene is astronomically large. These results raise the intriguing possibility that convergence in anatomical traits might sometimes be underpinned by convergence at the sequence level. Even more surprising, one of these genes leads to a well supported group of these bats with echolocating dolphins. We have studied 'hearing genes' in bats and whales, and found that evolutionary trees based on four of these genes all unite echolocating bats into a single but technically incorrect group. This finding has led to a revision of bat evolutionary relationships so raising the issue that echolocation has either been lost by the fruit bats, or has evolved more than once by convergence. For many years, echolocating bats were separated from fruit bats however, advances in our ability to resolve species' relationships provided irrefutable evidence that some echolocating bats were in fact more related to the fruit bats than they were to each other. ![]() It is seen at its most sophisticated in some lineages of bats and whales. Echolocation involves the production of sonar pulses and processing of the returning echoes for hunting and orientation, and poses particular challenges for high frequency hearing. We have recently identified several examples of apparent convergence in a suite of genes involved in hearing in different groups of echolocating mammal. Yet though examples of convergence are extremely common in the tree of life, we understand very little about the extent to which convergent evolution happens at the genetic level, in sequences of DNA and the proteins that they code for. The fact that similar structures have evolved several times suggests that they evolved to perform similar functions, so convergent evolution is powerful evidence that natural selection has shaped these features - there can be little doubt that bat and bird wings both evolved to allow powered flight, for example. ![]() Classic examples include the vertebrate wing, which has independently evolved a number of times, for example in bats, birds and pterosaurs, and the similar image-forming eyes of vertebrates and some invertebrates such as squid. Convergent evolution is the independent origin of the same feature in different groups of living things.
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