Yesterday, my eye was caught by a post written by Ed Yong over at Not Exactly Rocket Science about two recent studies showing that the echolocational abilities of bats and whales are both based on the same 14 amino acid changes to a single gene, Prestin. It can be universally acknowledged that morphologically, phenotypically, and geographically, bats and whales are highly dissimilar species. Yet both bats and toothed whales use echolocation for navigation in environments hostile to more traditional photon-based sight. And although the exact mechanisms behind the ability of echolocate are different in bats and whales (as might be expected given the dissimilar physiologies and habitats), the two groups share a strong genetic similarity in Prestin. So strong, in fact, that a phylogeny drawn using the DNA sequences of Prestin places all echolocating mammals as close relatives, excluding established evolutionary relatives such as other bats and whales who do not echolocated.
This case of convergent evolution is made more interesting because of the extreme behavioral differences in the way whales and bats practice echolocation. Bats echolocate through the medium of air, creating their sonar pulses via their voicebox. Whales echolocate through water by passing air through their nasal bones. These mechanistic differences are too great to be encoded by a single similar genes. Indeed, Prestin does not per say confer the ability to generate echolocation signals upon bats and whales. Instead, Prestin confers the ability to detect the rebounding echos, altering outer hair cells to make them more sensitive to the ultrasonic frequencies used in echolocation. With their enhanced ability to detect high frequency sounds, bats and whales evolved distinct physiologies to generate those sounds, as mediated by the demands of their distinct environments.
As Ed Yong points out, the independent replication of such distinctive genetic changes, resulting in the generation of distinct mechanisms to take advantage of the shared ability, is frankly astounding. Yet again, convergent evolution reinforces the duality of beautiful complexity and mysterious simplicity in the natural world.
Echolocation in bats and whales based on same changes to same gene. By Ed Yong at Not Exactly Rocket Science.
The original papers: