On October 2nd, Oregon State University published an article that showed a severe loss of maternal DNA lineages among blue, fin, and humpback whales over the course of the 20th and 21st century, resulting in the loss of their genetic diversity. What is maternal DNA, you may ask, and how does it relate to their diversity?
According to the study’s lead author, Dr. Angela Sremba, “A maternal lineage is often associated with an animal’s cultural memories such as feeding and breeding locations that are passed from one generation to the next.” If the lineage is lost, then the knowledge or instinct from their mother is also gone.
South Georgia is an island within the South Atlantic Ocean, 800 miles from the Falkland Islands, that was home to many whaling stations in the 20th century. Though it was a feeding station for whales, more than two million whales were killed there by commercial whaling. Therefore, for the past 60 years, sightings of whales in the South Georgia feeding grounds have remained low. The deaths of so many whales caused the end of many lineages, which led to a loss of cultural memory.
In order to analyze how whaling and the loss of maternal DNA (mtDNA) might have affected the diversity, researchers from Oregon State University gathered samples of DNA from today’s whale population and compared them to those from the pre-whaling era. They found that surprisingly, the rates of genetic diversity stayed relatively the same. However, whales can live for more than one hundred years, so most of the whales are likely to be the ones that were born during the pre-whaling era.
This discovery isn't particularly helpful since scientists are still unsure about what will happen when the whales from the past start dying. The next generation of these whales will also continue to have a further loss of maternal DNA, as we cannot depend on the minimal possibility that all of their offspring will be female and have children to pass their maternal DNA to the next generation.