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Koala genome reveals its secrets

20 November 2015

A groundbreaking study of the koala genome has revealed koalas are genetically diverse, indicating declining populations are the result of human-related activity rather than mating with kin. The work across a number of organisations also questioned the current recognition of the existence of three sub-species in southern and northern Australia, finding there was little evidence that there were different species.

These results show the genetic diversity of the koalas on the east coast of Australia is far from being inbred.
Professor Herman Raadsma

Southern koala image sourced from James Cook University. Northern koalas have thinner fur and are smaller and lighter in colour than their southern counterparts.

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

For the first time the genome of the koala (Phascolarctos cinereus) has been studied across the species range, revealing that koalas have good levels of genetic diversity.

Previous research has shown many marsupials have low genetic diversity, which is often a sign of inbreeding and mating with kin and is not unusual in animals with declining populations.

This new study, conducted in partnership with San Diego Zoo and the non-government organisation, Science for Wildlife, used cutting-edge genetic technology to answer critical questions about koala conservation.

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

The findings were published recently in the journal Conservation Genetics.

Professor Herman Raadsma from the University of Sydney’s Faculty of Veterinary Science said contrary to popular opinion, the research showed koalas were as diverse as many other wild species.

“These results show the genetic diversity of the koalas sampled from all key locations on the east coast of Australia is far from being inbred,” Professor Raadsma said.

James Cook University’s Associate Professor Kyall Zenger said the finding was exciting, given that koala numbers had been declining to the point where they were listed 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,” Associate Professor Zenger said.

Shannon Kjeldsen, a PhD student working on the project at James Cook University, said her research also showed that although koalas varied greatly in appearance in southern and northern Australia, there was very little evidence that there were different species – bringing into question the current recognition of the existence of three distinct sub-species.

“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.

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,” Associate Professor Zenger said.

The universities are working with Dr Kellie Leigh from Science for Wildlife and Jennifer Tobey from the San Diego Institute for Conservation Research.

Science for Wildlife director Dr Leigh said the development was extremely exciting. “It offers a tool to understand how all koala populations are genetically linked,” Dr Leigh said. The tool should also enable better management of 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.”

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