Scientists Map DNA of the Elephant Family

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A team of international scientists involving the University of Adelaide have today published the first map of the elephant family’s genomic history. The research confirms there are three species of modern elephant, rather than just the two commonly known African and Asian elephants.

The University of Adelaide component of the study has also led to a new and novel approach for reconstructing evolutionary relationships between species, which the researchers say is likely to be invaluable in mapping the evolutionary trees of other animals.

Published in the journal Proceedings of the National Academy of Sciences (PNAS), the researchers revealed the complex evolutionary relationships between today’s three remaining living species and ancient extinct relatives, including the mammoths and mastodons.

They showed that far from the earlier, simple two-branched evolutionary family tree model, interbreeding (and therefore gene flow) between species has been common in the past.

“Elephants and their ancient relatives like the woolly mammoths and mastodons have long fascinated people the world over. But until now there has been no comprehensive assessment of their evolutionary relationships,” says Professor David Adelson, Director of the University of Adelaide’s Bioinformatics Hub.

“The most surprising result was the degree of interbreeding between species. We didn’t really expect there would be gene flow between the mammoths and mastodons and the ancestors of modern elephants, but our results showed frequent interbreeding,”he says.

Professor Adelson has been involved in the first genome sequencing of the cow and horse genome in 2009, and now the elephant family genome.

The researchers reported 14 new genomes: two from each of the three living species (African savannah, African forest and Asian elephants) and extinct species: one straight-tusked elephant, four woolly mammoths, one Columbian mammoth and two American mastodons.

The findings confirm that the African savannah and forest elephants are two distinct species –an issue that has been under debatefor some time.

The data revealed nearly complete isolation between the ancestors of African savannah and forest elephants for about 500,000 years, providing compelling evidence for their definition as separate species.

The University of Adelaide devised an independent new method for resolving species differences, using a completely different type of DNA marker than that used elsewhere.

“Our method was essential to independently confirm the accurate evolutionary relationships and the correct reconstruction of the family tree,” says Dr Atma Ivancevic, postdoctoral researcherin the University of Adelaide’s Adelaide Medical School.

“The really exciting thing is that this will be applicable to other species. It’s a very quickway of figuring out whether or not the species
are related.”

The research was led by scientists at the Harvard Medical School and the Broad Institute of MIT and Harvard

Source : The University of Adelaide