Australia's invasive rabbit population probably descends from two dozen wild English rabbits that arrived near Melbourne on Christmas Day 1859. This is now indicated by a genome analysis. According to the study, their pedigree gave the herd an advantage over rabbits that had already arrived on the continent earlier.
Rabbits have now entered most of the Australian continent and have catastrophic effects on the ecosystem there: they threaten around 300 plant and animal species and cause damage of hundreds of million dollars in agriculture every year.
According to historical records, the first wild rabbits (Oryctolagus cuniculus) in Australia probably arrived in Sydney in 1788 with the first settlers. Ships that brought rabbits docked on the coast for decades, but it was not until the second half of the 19th century that the population spread significantly, at a speed of 100 kilometers per year throughout the country.
The records also suggest that the spread of the rabbits is due to the delivery of animals, which was intended for a certain Thomas Austin in Barwon Park, southwest of today's Melbourne. His brother had caught the animals near the family seat in Baltonborough in the southwest of England.
The Australian rabbits come from Baltonsborough
Evolutionary geneticist Joel Alves from the University of Oxford and his colleagues wanted to find out if genetic data confirms the records. To do this, they analyzed the genetic material of 179 wild rabbits caught in Australia, New Zealand, France and the United Kingdom, as well as eight domestic rabbits of different breeds.
They found that most rabbits on the Australian mainland are genetically similar and have a mixed descent of wild and house rabbits. The Australian rabbits also had more rare alleles with rabbits from southwestland together than with those from other parts of the United Kingdom. As a result, they actually actually come from Baltonborough. When looking at the mitochondrial DNA, which is inherited via the maternal line, the researchers came to the conclusion that most Australian mainland rabbits descended from around five females brought in from Europe.
In addition, the genetic diversity of rabbits decreased the further the animals were caught from Barwon Park, and alleles, which are rare or absent in wild rabbits, increased. According to the researchers, these patterns are consistent with the idea that most rabbits in Australia come from Barwon Park. The team reports on its results in "PNAS" on August 22, 2022.
"This is a very exciting work on a very important and well -examined topic," says Martin Nuñez, who is researching ecological invasions at the University of Houston in Texas. Using gene analyzes to understand how unwanted animal invasions begin can help to predict future invasions.
Wild rabbits had an advantage over domestic rabbits
Overall, the team finds that the wild descent of the rabbits was an important factor for them to spread across the entire continent. "Wild rabbits are different," says Alves. For example, they tend to flee from stressful situations and dig caves. According to the evolutionary geneticist, they were probably better able to avoid predators and survive in difficult terrain. Historical records indicate that Austin requested wild rabbits, while the previously imported rabbits were mainly house rabbits.
The fact that grazing land was increasing at this time and predators were increasingly kept at bay may also have favored their spread. "You had the right rabbits in the right place at the right time, with the right changes in the environment," explains Alves.
"The genetic analyzes seem to be very solid," says Australian geneticist Amy Iannella, who also deals with rabbits. In their eyes, the animals also helped to spread the fact that people transported them to other parts of the country, where they could also furnish themselves at home. Rabbits are typical community animals and need a shelter to survive. Young animals rarely moved on than a kilometer. "The idea that the rabbits spread over the whole country so quickly after a single release seems extreme when you consider what we know about their ecology."
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