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Whale of a Family Tree

Baleen whales have a complicated family tree, the New York Times reports. It adds that researchers have long wondered which species of baleen whale arose first, but that the morphological and molecular data is contradictory.

Researchers from Germany and Sweden have sequenced the blue whale Balaenoptera musculus and five other baleen whales to tease out their relationships to one another. As they report in Science Advances this week, the researchers constructed phylogenetic trees to find that rorquals, the largest group of baleen whales, radiated quickly about 10.5 million to 7.5 million years ago, a time that coincided with shifts in ocean circulation. They also report that rorquals don't have lineages that branch orderly in two like most mammals, but instead have phylogenetic networks. For instance, the three lineages of blue and sei whales; gray whales; and fin and humpback whales all arose at the same time.

Additionally, the researchers say their findings imply that rorqual speciation took place with concomitant gene flow.

"Whales can tell us new stories of how species can evolve into different forms," senior author Axel Janke from the Senckenberg Biodiversity and Climate Research Center and Goethe University Frankfurt tells the Times