Just like animals on remote islands, whale lice species would evolve independently on whales that are geographically isolated, the researchers say.
The right whale was once a single species, but changes in land formations and ocean currents over millions of years eventually isolated groups of the whale species in three distinct regions: the North Atlantic, North Pacific, and southern oceans.
Right whales have been hunted extensively for the past 1,000 years. The name was coined by whalers, who considered the species the "right" whale to hunt because its blubber makes dead whales float, aiding recovery of the carcass.
About 300 right whales live in the northwestern Atlantic Ocean. But the population is not particularly robust, and the animal is considered endangered.
A small population of a different species of right whale lives in the northern Pacific, but this group has been poorly studied, and exact numbers are unknown.
Southern ocean right whales are doing better: More than 8,000 exist, and their numbers are increasing at about 7 percent a year, according to the International Whaling Commission.
Studying the whales' genetic history could help conservationists better understand how to protect the animal from further population decline. But whale evolution is a difficult path to trace.
Stephen R. Palumbi, a professor of biological sciences at Stanford University in California, said whale DNA is "ticking at a slow rate, and this obscures information about population size changes over time."
In other words, genetic changes in the whale lice happen faster and are therefore easier to trace than those in whales.
This, Palumbi said, "may be a way to infer past whale population changes."
Saving Right Whales
The University of Utah researchers found that the three whale lice species living on right whales in each region were different genetically from their counterparts.
The scientists also found high genetic variation between the parasites. Determining the rate of genetic change allowed the scientists to determine how long ago the right whale split into three species.
In addition, Jon Seger, a co-author of the study and professor of biology at the University of Utah, says high genetic variation is good news for whale conservation. It may mean that northern right whales fairly recently had populations just as large as their southern counterparts.
"The finding suggests that the northern right whales are suffering only from recent population reduction, not from a long history of small population size and reduced genetic variation," Seger said.
If the whale population had been small and struggling for a long period of time, genetic variationboth for the whales and their parasiteswould start to disappear. In this case, inbreeding would lead to genetic diseases that would make it difficult for the whale population to bounce back.
But Palumbi, the Stanford biologist, says that the findings may not mean much for the future of whale conservation.
"The right whales are in desperate trouble, and the lice neither tell us that more strongly than we knew before, nor tell us new things to do about it."
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