Researchers say genetic markers show important differences for conservation goals
By Summit Voice
SUMMIT COUNTY — Marine biologists have long thought the world’s killer whale populations might be made up of more than one species, but they haven’t been able to do enough genetic mapping to be sure — until now.
In a report published last week in Genome Research, scientists with the Southwest Fisheries Science Center of the National Oceanic and Atmospheric Administration reported finding strong evidence of multiple species. The researchers say their conclusions are important because it will help resource managers establish conservation priorities and to better understand the ecological role of one of the oceans’ top predators.
As a result of the study, two types of killer whales in the Antarctic that eat fish and seals, respectively, are suggested as separate species, along with mammal-eating “transient” killer whales in the North Pacific. Several other types of killer whales may also be separate species or subspecies, but additional analysis is required.
“The genetic makeup of mitochondria in killer whales, like other cetaceans, changes very little over time, which makes it difficult to detect any differentiation in recently evolved species without looking at the entire genome,” said Phillip Morin, lead author of the NOAA study. “But by using a relatively new method called, ‘highly parallel sequencing’ to map the entire genome of the cell’s mitochondria from a worldwide sample of killer whales, we were able to see clear differences among the species.”
In all, tissue samples from 139 killer whales were analyzed. Samples came from killer whales found in the North Pacific, the North Atlantic and oceans surrounding Antarctica.
The new genetic sequencing is far faster and less costly than historical methods of analysis. For instance, the examination of mitochondrial DNA genome in one sample could have taken as long as several months. But with the use of high throughput sequencing, researchers can complete the same analysis for 50 or more samples in just a few weeks, and technology to sequence larger parts of the genome and more individuals continues to improve rapidly.