The Penguin Post has learned that King Penguins on the sub-Antarctic Macquarie Island are showing healthy levels of genetic diversity after coming back from the brink of extinction. This is positive news for the penguins as genetic variability is important for the long-term health and survival of a species because it helps a population to adapt when faced with environmental changes or diseases. King Penguins were decimated by humans during the 1800s, but due to conservation efforts they are now thriving on Macquarie Island, which is located in the Southern Ocean between Australia and Antarctica. “The conservation program has been particularly successful in getting the population back to its natural size and genetic diversity,” said lead author and evolutionary biologist Tim Heupink from Griffith University in Queensland of a study published in Biology Letters today.
Penguins hunted for blubber oil At around 90 cm tall, King Penguins are the second largest penguins in the world (Emperor penguins are the biggest). Thousands lived on Macquarie Island until humans arrived in 1810 and began hunting them for their blubber oil. After years of human exploitation, the penguin population was reduced to a single, very small colony, and several conservation measures were introduced to aid their recovery. Macquarie Island was declared a wildlife sanctuary in 1933 and given World Heritage status in 1997. Fishing was also controlled, and pests, such as cats, were eradicated. This allowed the penguins to flourish once again. Their population increased and they recolonised previous breeding sites, expanding their range over the island.
The bottleneck effect Populations that have been reduced to a very small size can suffer from the ‘bottleneck effect’. This happens when the few surviving individuals represent a small genetic sample of the population, and the variability of the gene pool is reduced and may remain so even when numbers increase again. But genetic analyses in this study found that this has not occurred in the Macquarie Island King Penguins. Heupink’s team extracted DNA from the penguins currently on the island and also from the bones of 1,000-year-old King Penguin fossils. They used sequencing machines to assess the amount of variability within the DNA pieces and then compared the modern and ancient penguin samples.
Bouncing back from the brink The team found that the genetic diversity for the ancient and current populations of King Penguins was approximately the same. This outcome is unique, as similar ancient DNA studies of threatened animals have shown the opposite result, explaining why species often do not recover after a sharp population decline. “The genetic diversity of King Penguins is now the same as it used to be 1,000 years ago. This means that the population is healthy and adaptable to future changes,” said Heupink. Craig Miller, an evolutionary geneticist at the University of Auckland in New Zealand, commented on the findings. “Despite the Macquarie Island populations of King Penguins being driven to the brink of extinction, they have recovered their pre-exploitation levels of genetic variation in a relatively short period. This is likely to be due to that fact that the population, although significantly reduced in size, did not stay in the ‘bottleneck’ for a long period of time,” he said. Once the island became a wildlife sanctuary, the penguin population was able to grow rapidly, which increased the chances of retaining a variety of genetic traits, including the rare ones. Strong population growth also decreased the likelihood of inbreeding. “The study shows that if managed correctly, even populations close to extinction can recover quickly, both in terms of their numbers and levels of genetic variation,” said Miller.