Evolution of marine mammals

A study of the genetic similarities between distantly-related marine mammals is presented in an article published online this week in Nature Genetics. The findings increase our understanding of how similar traits evolved in marine mammals.

Marine mammals, such as whales and manatees, from distinct mammalian groups, share traits required for adaptation to a marine environment even though they evolved those traits independently. This phenomenon is known as convergent evolution. To better understand the genetic basis of convergent evolution in marine mammals, Andrew Foote and colleagues sequenced the genomes of the killer whale, walrus and manatee and improved the genome sequence for the bottlenose dolphin.

They identified 191 genes that had been selected for during evolution across all four species. They suggest that these genes are likely to be related to the shift from terrestrial to marine life, with eight of them undergoing identical molecular changes in all four species. A further seven genes had undergone identical changes in all the species studied, but only showed evidence of being involved in adaptation in one or two species. Some of these genes have roles in processes important to marine adaptation, such as bone formation, inner ear formation and regulation of blood coagulation.