Koalas are a type of marsupial endemic to Australia. They live on a specialised diet of eucalyptus leaves and are renowned for sleeping most of the day! Despite their status as an iconic Australian animal, koalas are classified as Vulnerable by the IUCN Red List, indicating that they face a risk of extinction in the wild.
During the 19th and 20th centuries, koalas were hunted for their fur. An estimated 8 million koalas were killed between 1888 and 1927. Their fur was sold across the world, including auction houses in London, where it would then go on to be made into coats and hats. These killings resulted in the koalas being deemed functionally extinct (where a population is too small to sustain itself) in South Australia in 1912. In present day, it is estimated that there are less than 90,000 koalas in the wild.
This population crash resulted in a population bottleneck, an event which reduces genetic diversity and increases inbreeding. Given time, the remaining population can suffer genetic damage, such as reduced fertility and lower survival rates. It may even trigger an “extinction vortex” – defined by scientists as a self-reinforcing process in which a small population declines towards extinction.
The study indicated that recombination may have played a big role in the koalas’ recovery.
When a species is considered to have low genetic diversity, many conservationists believe it is unlikely to recover. The koalas, however, exceeded expectations. Researchers analysed 418 koalas from 27 populations across the country, and whilst they still had relatively low genetic diversity, the marsupials were showing signs of genetic recovery! The study indicated that recombination may have played a big role in the koalas’ recovery. Recombination is when DNA is shuffled into new combinations during meiosis – a process by which gametes (eggs and sperm) are produced. Rapid population expansion led to an increase in recombination, which lead to offspring with different combinations of genes from their parents. Overall, helping functional diversity be restored as the population grows.
Many species in the world suffer from low genetic diversity: cheetahs, sea otters, Tasmanian devils. Thanks to the koalas, these newly found insights could be valuable for conservation strategies focused on the long-term survival of threatened wildlife populations.