Ancient DNA and King Penguin Populations
Macquarie Island is an isolated island of the South Pacific, located roughly half-way between Australia and New Zealand and quite far to the south of both. The island is home to King Penguins, and recently a team of biologists published a study of ancient and modern penguin DNA from bones collected on the island, some of them up to 8,000 years old, to reconstruct patterns in genetic diversity in the early and modern history of this island.
These samples reveal patterns in genetic diversity of King Penguins over a period of great stress. Two King Penguin colonies were originally present on Macquarie Island. Sadly, human settlers wiped out all of the penguins in the colony at the Isthmus (the northmost part of the island) by 1894 and reduced the population at Lusitania Bay to about 3400 birds – a tiny fraction of the original population.
Sounds like the final days before a tragic loss of the entire islands penguin fauna. However, just in time, Macquarie Island was made a wildlife refuge in 1930. Over the next 80 years the penguins rebounded and some birds from the Lusitania Bay colony moved north along the coast and re-started the Isthmus colony. One of the interesting things that the DNA study revealed is that the penguin have reached levels of genetic diversity close to those that existed before human arrival. Genetic diversity is important. A plunge in the number of genotypes can leave populations vulnerable to genetic disorders carried on recessive genes. Higher genetic diversity also provides resilience to changing environments. While many ancient DNA studies have revealed that population crashes can result in genetic bottlenecks, the Macquarie Island penguins seem to have rebounded – possibly through fortuitous survival of genetically diverse individuals and perhaps also through arrival of a few King Penguins from other areas of the southern oceans.
Thanks to protections put in place, there are almost half a million King Penguins living on Macquarie Island today. A hopeful conclusion of this study is that even after being severely pressured, penguins can rebound if we just allow them the chance
Heupink, T.H., J. van den Hoff, and D.M. Lambert. In press. King penguin population on Macquarie Island recovers ancient DNA diversity after heavy exploitation in historic times. Biology Letters.