For most of its existence, European rabbits were confined to the Iberian Peninsula and southern France.The Romans dispersed the species, and this spread accelerated during the Middle Ages.

Rabbits were first introduced to mainland Australia in 1788 when the 1st Fleet brought five livestock to Sydney. At least 90 were subsequently imported by 1859, but none of these populations became invasive.

Within 50 years, however, rabbits have spread across the continent at a rate of 100 km per year, the fastest colonization rate of any introduced mammal ever recorded.

So what changed after 1859 and how did the invasions begin?

Historians and Australians have long believed that the country’s “rabbit plague” began at Barwon Park. thomas Austinnear Geelong in Victoria.

In a study published in PNASan international team led by the University of Cambridge and the CIBIO Institute in Portugal has finally provided genetic evidence for this version of the event and settled the debate as to whether the invasion occurred from a single or multiple independent introductions. was attached.

On October 6, 1859, Austin’s brother, William, shipped off wild rabbits captured on his family’s land at Bartonsborough, Somerset, along with domestic rabbits. Thunder.

On Christmas Day, 24 rabbits arrived in Melbourne and were dispatched to Barwon Park. According to reports in local newspapers and Austin himself, within three years the number of “Austin rabbits” had grown into the thousands.

Researchers study the historical record with new genetic data collected from 187 “European rabbits” wild-caught in Australia, Tasmania, New Zealand, the United Kingdom and France between 1865 and 2018. Did.

• Where did the Australian invasive rabbit come from?
• Whether the aggression resulted from a single or multiple introductions.
• how they spread across the country.
• Whether there was a genetic explanation for their success compared to other imported rabbit populations.

Recent research has challenged the single-origin hypothesis, arguing instead that invasive rabbits arose from several independent introductions. Significant, ancestral European and domestic populations were not sampled.

“We have been able to trace the ancestry of Australia’s invasive populations to the southwest of England, where the Austin family collected rabbits in 1859,” says lead author, now at the University of Oxford and the CIBIO Institute. explains Dr. Joel Alves, a researcher at .

“Our findings suggest that, despite numerous introductions across Australia, it was a single batch of British rabbits that caused this devastating biological invasion, and the impact is still felt today. It shows that you are feeling it.

The researchers found that as rabbits moved further away from Barwon Park, genetic diversity declined and rare genetic variations occurring in rapidly growing populations became more frequent.

Despite the construction of rabbit fences, the deliberate introduction of the myxoma virus, and other measures, rabbits remain one of Australia’s major invasive species, threatening native flora and fauna, and reducing agriculture. It costs the sector an estimated $200 million annually.

Previous studies have suggested that several factors contribute to biological invasion, including population size, number of introductions, and environmental changes.

New findings suggest that the genetic make-up of these animals may have an impact.

The researchers note that if the trigger for the invasion was environmental change, such as extensive pasture development by human settlers, it was likely that multiple local rabbit populations expanded. increase. The genetic findings of this study and the failure of rabbits to become invasive prior to 1859 undermined this possibility.

Instead, the team investigated the possibility that the arrival of specific genetic traits acted as triggers for invasion. This helps explain the overwhelming genetic evidence for a single introduction.

A newcomer with a genetic advantage

Rabbits introduced to Australia before 1859 were often described as exhibiting domesticated, showy coat colors, drooping ears, and traits associated with domestic breeds but not normally found in wild animals. The Austin rabbits were described at the time as being wild-caught, but the genetic findings of a new study prove that at least some of these animals were in fact wild.

Professor Francis Giggins of Cambridge University’s Department of Genetics says there are a number of traits that make wild domestic rabbits unsuitable for survival in the wild. “However, it may have lacked the necessary genetic mutations to adapt to Australia’s arid and semi-arid climates.

“To combat this, Australian rabbits have evolved body shape changes to control their body temperature. , may have been genetically advantageous.”

In the 20th century, Joan Palmer recalled that her grandfather, William Austen, found it difficult to procure animals for Thomas:

Because wild rabbits were never common around Bartonsborough. It was with great difficulty that he managed to score six. These were half-grown specimens that had been removed from the nest and domesticated. To supplement that number, he purchased seven gray rabbits that the villagers kept in huts as pets or to eat.

Alves and Jiggins found that invasive rabbits, descended from Austin imports, contained considerable elements of domestic ancestry, and that shipped wild and domestic rabbits were more likely than 80 It supports Joan Palmer’s claim that they bred before or during the day’s journey, and why more rabbits arrived than were sent.

“Changes in the environment may have made Australia vulnerable to invasion. But what sparked one of the most iconic biological invasions of all time was the genes of small herds of wild rabbits. It was a composition.”

“This is a reminder that the actions of just one or a few people can have a devastating impact on the environment.”

reference: Alves JM, Carneiro M, Day JP, et al. It was a single introduction of wild rabbits that triggered the biological invasion of Australia. Proceedings National Academy.science2022;119(35):e2122734119. Doi: 10.1073/pnas.2122734119

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