An unplanned genetic experiment
In the 1930s, koalas (Phascolarctos cinereus) were introduced to Magnetic Island as a safeguard against perceived threats on the Australian mainland. This action, intended for conservation, initiated an unplanned, long-term experiment in population genetics. With no natural predators on the island, the koala population expanded. Genetic studies of island populations like this one show the consequences of habitat fragmentation for the species. Today, the island has Northern Australia's largest wild koala population, with a 2012 study estimating around 825 individuals in the national park.
The isolation of the Magnetic Island koalas has led to genetic divergence from their mainland ancestors. This, known as the founder effect, occurs when a new population is established by a small number of individuals, whose gene pool may differ by chance from the source population. Over generations, this genetic drift can lead to a population with distinct characteristics. The koalas have adapted specifically to the island's environment and its particular varieties of eucalyptus, further distinguishing them from mainland populations.