Koala genome reveals its secret

It has long been thought that low levels of koala genetic diversity is a reason for their declining populations and local extinctions, but James Cook University and University of Sydney researchers have found this is not the case.

James Cook University
Koalas still maintain higher levels of genetic diversity than originally thought
For the first time, the genome of the koala (Phascolarctos cinereus) has been studied across the species range. Previous research has shown that many marsupials have low genetic diversity—often a sign of inbreeding and mating with kin, which is not unusual in animals with declining populations.

A new study by researchers at JCU and the University of Sydney, in partnership with the NGO Science for Wildlife organisation and San Diego Zoo, has used cutting-edge genetic technology to answer critical questions about koala conservation.

In the ground-breaking study, the group has applied whole-genome DNA sequencing to show that koalas still maintain higher levels of genetic diversity than originally thought.

JCU’s Associate Professor Kyall Zenger said the finding was very exciting, given that koala numbers have been declining to the point where they have been listed as being at risk of becoming endangered.

“To effectively manage koalas across Australia and in captivity we must understand how genetically diverse these populations are—how ‘fit’ they are,” he said.

Shannon Kjeldsen, a PhD student working on the project at James Cook University, said her research also showed that there is very little evidence for the three currently recognised subspecies of koalas.
“It’s widely thought that there are three distinct subspecies of koala inhabiting Southern and Northern Australia, respectively,” she said.

Northern koalas have been known to be smaller and lighter in colour than their southern counterparts, which are larger, darker and have thicker fur.

“We know that it would be unwise to move koalas between these regions, because they live in different climates and have adapted to different environments, but we do not know where the management boundaries lie,” Ms Kjeldsen said.

The duo is working alongside Professor Herman Raadsma from Sydney University, Dr Kellie Leigh from Science for Wildlife, and Ms Jennifer Tobey from the San Diego Institute for Conservation Research.

Associate Professor Zenger said management and implementation of a national koala conservation program was vitally important to protect this charismatic species.

“Until now there has been a lack of species-wide information to help coordinate conservation efforts,” he said.

“These results have shown the genetic diversity of the koalas sampled from all key locations on the east coast of Australia is far from being inbred, and actually is as diverse as many other wild species.”

Science for Wildlife Inc Director, Dr Kellie Leigh said: “This development is extremely exciting, in that it offers a tool to understand how all koala populations are genetically linked.”

The tool also offers exciting possibilities to better manage captive breeding populations.

Ms Tobey said, “The Australian research gives for the first time a clear view on how captive populations can be mapped to the national koala population, and to manage breeding to maximise genetic diversity.”

This project is funded and supported by an Australian Research Council (ARC) Linkage Project grant, with industry funding and in-kind support from partners San Diego Zoo Koala Education & Conservation Program and James Cook University, Sydney University, and Science for Wildlife.

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