202 — Convergent sequence evolution between echolocating bats and dolphins

Echolocation requires a specialized auditory system that is very highly sensitive to high-frequency signals. It has been concluded for some time that the Prestin motor protein is responsible for the outer hair cell (OHC) high frequency sensitivity in humans and other mammals, and recent research demonstrated that Prestin was responsible for enabling high-frequency echolocation capabilities in bats. Certain nucleotide mutations in the gene that codes for Prestin altered the molecule in such a way that it heightened the discriminability and detectability of such high-frequency signals.

This research reports that the mechanism for echolocation in dolphins actually arose by very similar path: Similar amino acids are changed in the bat Prestin and dolphin Prestin genes. We know that these echolocative capabilities arose separately in dolphins and bats (this is obvious just by looking at the mammalian family tree), and the production component of echolocation — the audio synthesis — varies dramatically between the species. (Bats produce chirps in a manner very different to how dolphins produce their clicks.)

That means that this phenotypic consistency at the molecular level is a perfect example of convergent evolution: The two animals had very similar needs, and almost perfectly matched each other when evolving their solutions to this problem.

One fascinating (and coincidental) surprise is that this research on convergence was reported by two labs almost simultaneously.