Time to revise right whales' family tree?

Genetic analysis of nearly 400 right whales from around the world indicates there may be a new, third branch on this mammal's family tree.

Scientists had agreed on two species of right whale: the northern and the southern. The endangered northern species has Atlantic and Pacific populations.

A new statistical analysis of DNA from almost all known right whale communities indicates the two northern populations may constitute distinct species. Even more surprising, the researchers say, the North Pacific animals bear a closer genetic resemblance to southern right whales than to their North Atlantic counterparts. These findings, which could add urgency to right whale conservation, appear in the November MOLECULAR ECOLOGY.

A team of researchers from around the world extracted DNA from tissue samples of 385 right whales representing nearly all the animals' far-flung dwelling-places. For the most elusive groups, scientists took DNA from preserved specimens dating as far back as 1850.

The researchers examined DNA from the animals' mitochondria, the power generators in cells. Mitochondrial-DNA sequences are useful in taxonomy because they change more rapidly than DNA in the nucleus does.

By comparing the same segments of DNA from every whale they studied, scientists found 10 positions that identify the North Atlantic, North Pacific, or southern right whale. Seven of these 10 positions consistently distinguished one northern population from the other

"This supports a distinct genetic lineage for North Pacific right whales," says the paper's lead author, Howard C. Rosenbaum of the American Museum of Natural History in New York City.

Critics say that the DNA differences don't necessarily signify separate species.

Classifying the North Pacific and North Atlantic populations as separate species--instantly reducing their respective population counts--could boost efforts to save them, scientists say. The North Atlantic right whales are projected to become extinct in about 200 years if they continue to die out at the current rate.

Some scientists committed to whale conservation say more data are needed to determine whether the North Pacific right whale is a separate species. "The amount of genetic difference seen ... in this study is at the same level as what's seen within other recognized species such as the humpback whale," says Per J. Palsboll, a molecular ecologist specializing in whales at the University of Wales in Bangor, United Kingdom.

"One needs longer DNA sequences, including protein-coding regions, from each geographic area for comparison," adds evolutionary geneticist Ulfur Arnason of Lund University in Sweden.