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Kangaroo Island’s koalas have long been seen as a symbol of resilience, but new research from Flinders University suggests their survival story comes with a genetic catch.
Scientists have found that the island’s population, while abundant and largely disease-free, carries significantly reduced genetic diversity compared to mainland koalas. This is because today’s thousands of koalas descend from fewer than two dozen animals relocated from Victoria in the 1920s, when the species was under threat from hunting and habitat loss.
Lead researcher Dr Katie Gates said that although the population had flourished in numbers, the koalas’ genetic makeup showed worrying signs of inbreeding. “Kangaroo Island koalas are a successful conservation story in terms of population size. But their genetic health tells a different story. Their limited diversity and high inbreeding means they might struggle to adapt to future threats like disease or climate change,” she said.
By sequencing whole genomes, the team found that Kangaroo Island koalas had many more “runs of homozygosity”—long stretches of identical DNA inherited from both parents. This pattern increases the likelihood of harmful variants being expressed, raising the risk of fertility issues and developmental abnormalities.
While the population has so far resisted diseases such as chlamydia and koala retrovirus, its reduced genetic resilience could leave it exposed if outbreaks occur. The findings highlight the importance of “genetic rescue” through the introduction of new individuals from diverse mainland populations.
Senior author Professor Luciano Beheregaray said Kangaroo Island could still play a crucial role in koala conservation, but only if proactive management is introduced. “Kangaroo Island has the potential to remain an important conservation refuge for koalas. But without genetic management, this ‘ark’ could become a trap. Our work highlights the importance of ongoing genomic monitoring for species managed in isolation,” he said.
The research also carries broader lessons for conservation efforts worldwide: while islands and fenced reserves can provide immediate protection for threatened wildlife, long-term success depends on maintaining genetic diversity.
