New findings by researchers at Flinders University have shown the low genetic diversity in a population of the blue whale is due to past natural events rather than recent whaling, giving new hope to the long-term survival of the world’s largest living animal.
The discovery, led by Biological Sciences researchers Dr Catherine Attard, Associate Professor Luciana Möller and Professor Luciano Beheregaray, was made using DNA from living blue whales (Balaenoptera musculus) to trace the history of changes in the species’ genetic diversity.
Dr Attard said the population of blue whales in Australia had the lowest recorded genetic diversity of blue whales in the world. This population represents one of the subspecies of blue whale, the pygmy blue whale.
“Their low genetic diversity could be caused by the dramatic drop in population size due to whaling, which can lead to inbreeding, inability of individuals to cope with future environmental change and, eventually, extinction of the population. However, a low genetic diversity can also be caused by natural events,” Dr Attard said.
“We used information in the DNA of living blue whales to trace their past. We found that blue whales came to Australia only about 20,000 years ago, which means the population is very young. This accounts for their low genetic diversity as it takes time for a population to build up genetic diversity,” Associate Professor Möller said.
Professor Beheregaray said the genetic analyses also indicated that the population of blue whales in Australia were likely founded from Antarctic blue whales, which are a different subspecies of blue whale.
“A small number of Antarctic blue whales probably ventured to Australia because of natural changes in climate and then they decided to stay. This means that historical climate change has shaped the evolution of blue whales into different subspecies,” he said.
Blue whales are currently endangered because of 20th century whaling and are still at critically low numbers.
Dr Attard said the study revealed that the low genetic diversity of blue whales from Australia was natural and had been a characteristic of these blue whales for thousands of years. This means their recovery is not likely to be inhibited by their low genetic diversity, but may be inhibited by current anthropogenic impacts, such as marine pollution and marine noise.
The findings are published in the latest edition of The Royal Society journal Biology Letters.
The study was a collaborative effort that included researchers from the Centre for Whale Research, the Blue Whale Study and Deakin University in Australia, as well as from the University of Johannesburg in South Africa.
The genetic analyses were funded by the Australian Government and Australian organisations: the Australian Marine Mammal Centre within the Australian Antarctic Division, Flinders University, Macquarie University, and the Royal Zoological Society of New South Wales.