A koala’s sleepy demeanour hides a resilient genome. Despite being hunted to near extinction across Australia 200 years ago – thanks to the international fur trade – my colleagues and I have found that the koala genome remains remarkably diverse.
In a nation known for its extreme weather and environments, a species’ ability to adapt is crucial. Species that retain a high level of genetic variability can often better withstand environmental changes and emerging threats from disease.
Koalas became a protected species and their numbers have mostly bounced back. And you can see they’re physically different at the extremes of their range, from the larger, darker koalas of the south, to the smaller, lighter animals in the north.
But despite these differences it had long been assumed that, having being hunted to a few individuals, there would be low genetic diversity in koala populations across the country today.
We set out to see if this assumption was correct.
We genetically analysed 171 koalas from across Australia and compared their genomes. Amazingly, we not only found that koalas are genetically very diverse, but that their high diversity is comparable to other healthy wild species that weren’t hunted to near-extinction, such as the wild pig in Europe.
This data can be used for population management. In some regions koala numbers are booming, while in others they are dwindling to the point of local extinction. To manage a species effectively, we need to know how diverse these populations are, and more importantly, how different they are from one another.
Supplementing koala populations from other regions is illegal in much of Australia, but in areas of low diversity we should at least consider it – as long as the genetics and environments of the donor and receiving populations are thoroughly assessed.
It’s possible that in the past koalas were more genetically diverse, but without enough ancient samples, it’s hard to know. It is also possible that some pockets of high diversity escaped the worst of the hunting. Our next study, a broader genetic survey, should enable us to answer why the koala genome is so diverse. It will also gather the information we need to make sure their genetic diversity stays high.
Shannon Kjeldsen is an evolutionary biologist at James Cook University, Townsville.
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