Dolphins in the Bay of Bengal at the Forefront of Evolution

Scientists from the American Museum of Natural History have discovered that the Bay of Bengal could drive the evolution of new life forms. In collaboration with the Wildlife Conservation Society and Centre for Ecology, Evolution and Environmental Changes (Universidade de Lisboa), marine scientists have found two dolphin species in Bangladesh waters that are genetically distinct from those in other regions of the Indian and western Pacific Oceans.

The study, which was published in Conservation Genetics, followed the possibility of a new species of "river shark" in the same waters. DNA collected from both Indo-Pacific humpback dolphins (Sousa chinensis) and Indo-Pacific bottlenose dolphins (Tursiops aduncus) was compared, leading to the discovery that both populations of both species are distinctly different from populations in other parts of the Indian Ocean and western Pacific.

"Our findings indicate that there is a connection between the presence of these distinct populations of dolphins and the unique oceanic habitat that is found in the Bay of Bengal," said Dr. Ana R. Amaral from the Centre for Ecology, Evolution and Environmental Changes and the lead author of the study. "The combination of a biologically rich yet isolated seascape could be driving speciation, or the emergence of new species."

The Bay of Bengal is composed of freshwater and organic matter from the Meghna, Brahmaputra, and Ganges Rivers. A submarine canyon called the Swatch-of-No-Ground (SoNG) recycles nutrients through upwelling, resulting in a biologically productive coastal region with a complex interchange of currents that causes species to be separated from other parts of the Indian Ocean.

"The discovery of genetically distinct dolphin populations helps us to expand the body of knowledge of how these dolphin species have changed over time," shared Howard Rosenbaum, the Director of the Wildlife Conservation Society's Ocean Giants Program. "These results have significant implications for identifying unique marine mammal populations, which in turn have important conservation implications for safeguarding the long-term biodiversity in this region."