The study, published in Ecological Applications , was carried out by Professor Carolyn Hogg and Dr Elspeth McLennan from the Australasian Wildlife Genomics Group in the School of Environmental and Life Sciences .
The extensive map was created using data from the Koala Genome Survey , a joint initiative of the Australian and NSW governments to collect robust data about the genetic diversity of koalas across Australia and to inform conservation management.
In recent decades, koalas have come under increased pressure from threats such as disease, habitat destruction and catastrophic bushfires, which have reduced the animal to isolated patches of its former range. In 2022, the combined koala populations in New South Wales, Queensland and the Australian Capital Territory were listed as 'endangered' under the Environment Protection and Biodiversity Conservation Act 1999 .
The data shows that koalas in Queensland are the most genetically diverse at an individual level and koalas in New South Wales harbour the greatest number of genetic variants, making these populations critical for the long-term survival of the species. Koalas in Victoria, and in coastal areas of New South Wales and Queensland, have the least genetic variation.
Professor Carolyn Hogg
The report's senior author, Professor Hogg, said: "The loss of genetic diversity is a worrying trend that is being exacerbated by urban development, habitat destruction and climate change. Isolated populations are at higher risk of inbreeding, making them more susceptible to disease and vulnerable to future threats.
"If we want to see koalas in generations to come, we need to act now."
Genetic diversity of koalas across eastern Australia. Supplied: Dr Elspeth McLennan, University of Sydney.
The report outlines the measures that could be taken to increase genetic diversity in koala populations. Steps include creating wildlife corridors that allow them to move more freely and safely between areas and translocations (moving koalas from one area to another) to breed new genes into a population.
It is not only a decline in the overall genetic diversity of koala populations that is of concern to conservation scientists.
In research carried out by Professor Hogg and PhD candidate Luke Silver, recently published in Immunogenetics , the team observed that the diversity of immune genes in the koala population is also decreasing. With koalas affected by serious diseases such as chlamydia, the decline in the marsupial's immune genes is a worrying trend that could leave it more vulnerable to diseases in the future.
The authors also call for an end to state-based requirements in New South Wales and Queensland which stipulate koalas entering veterinary care must be returned to the place they are found. Often, koalas are brought into care after being hit by a car or attacked by a dog while moving to a new location. Providing koalas with safe corridors to move through are important in maintaining gene flow across the species' range.
Dr Elspeth McLennan
The study's lead author, Dr Elspeth McLennan, said: "Returning a recovered koala to a similar region, rather than the exact location, could not only have a significant impact on the likelihood of the koala being injured again, but would also promote genetic diversity by allowing the rescued animals to mix with other koala populations."
The research team at the Australasian Wildlife Genomics Group at the University of Sydney, working with scientists at the Australian Museum, were the first to fully map the genome of the koala in 2018.
Research and Declaration
Hogg, Carolyn, McLennan, Elspeth, et al. 'Genomics identifies koala populations at risk across eastern Australia' (Ecological Applications) DOI:10.1002/eap.3062
Silver, Luke, Hogg, Carolyn, et al. 'Using bioinformatics to investigate functional diversity: a case study of MHC diversity in koalas' (Immunogenetics) DOI: 10.1007/s00251-024-01356-6
Professor Hogg is a member of the NSW Expert Panel for koalas, an advisory panel to the NSW Government. Dr McLennan is a member of the National Koala Recovery Team Community Advisory Committee, an advisory committee to the Federal government.
