How do rabbits transition from adorable pets to invasive species? These animals have established populations across the globe, often leading to severe economic and ecological issues. However, the genetic mechanisms behind this phenomenon have remained unclear until now. A team of biologists analyzed the genomes of nearly 300 rabbits from three continents, uncovering the crucial genetic alterations that enable these creatures to excel as colonizers.
How do rabbits make the leap from being cuddly pets to aggressive invaders? They have successfully populated various countries around the globe, frequently resulting in significant economic and environmental repercussions. Until now, the key to this transformation has been a mystery. In a recent study published in the journal Nature Ecology and Evolution, an international group of scientists, led by researchers from BIOPOLIS-CIBIO (Portugal) and Uppsala University (Sweden), sequenced the genomes of nearly 300 rabbits from across three continents to reveal the critical genetic changes that allow these animals to become successful colonizers.
Throughout history, humans have cared for numerous animal species. Whether it’s your adorable kitten, faithful dog, or vibrant goldfish, domestication has led to a diverse array of pet forms. “Certain animals have diverged so dramatically from their wild ancestors that it’s astounding to consider their connection, like chihuahuas descending from wolves,” notes Dr. Pedro Andrade, a researcher at BIOPOLIS-CIBIO and first author of the study. “The changes can be so extraordinary that if you were to release your pet into the wild, it would find surviving very difficult.”
However, some do adapt when faced with the challenge. These are known as feral populations, which are groups of once-domestic animals that have successfully re-acclimated to the wilderness. Rabbits exemplify this process. Due to repeated and independent releases, rabbits have managed to establish populations in various regions worldwide. Yet, despite extensive research, a fundamental question remains: how can an animal domesticated for thousands of years not only survive but flourish after being reintroduced to the wild?
“In a prior study by our team regarding the introduction of rabbits to Australia, we discovered that domestic rabbits were released multiple times over several decades before a single introduction of just 24 rabbits with wild ancestry in 1859 by Thomas Austin spurred an explosive growth in the rabbit population, leading to one of history’s largest ecological disasters,” explains Dr. Joel Alves, a researcher at BIOPOLIS-CIBIO and the University of Oxford.
Could this be the reason behind the frequent establishment of feral rabbit populations? To investigate, the international research team sequenced the genomes of nearly 300 rabbits, which included six feral populations from Europe, South America, and Oceania, along with domestic and wild rabbits from their original habitat in Southwest Europe. With this extensive dataset, the largest genetic repository of rabbits ever compiled, researchers aimed to uncover what sets these invasive rabbits apart.
“Since domestic rabbits are so prevalent, we initially thought that feral populations would consist mainly of domestic rabbits that had readapted to the wild. However, our results suggest a more intricate picture,” said Dr. Miguel Carneiro, a senior author of the study. He added, “Despite analyzing six largely independent colonizations, all of these feral rabbits exhibit a mixed origin from both domestic and wild ancestry.”
The researchers discovered that as rabbits re-adapted to the wild, genetic variations associated with domestication were often lost, as these traits rendered the rabbits more susceptible to predators—a trend that intensified with the extent of changes made during the domestication process. “In these feral populations, it’s uncommon to find an albino or entirely black rabbit, even though such colors are often found in domestic rabbits. However, rabbits may possess a mutation for diluted coat color, a domestic trait that has limited impact on their ability to blend in,” adds Dr. Leif Andersson, a professor at Uppsala University, who also serves as a senior author of the study. He further remarks, “This illustrates natural selection at work.”
This elimination of domestic traits wasn’t limited to appearance. The researchers observed strong natural selection affecting genes related to behavior and neural development. “Tameness is vital for domesticated animals to cohabitate with humans, but it does little to aid a rabbit’s survival in the wild, prompting natural selection to remove the genetic variations associated with tameness,” states Dr. Andrade.
This research has significant implications for our understanding of evolution and will garner attention from policymakers and practitioners in conservation. Feral rabbits can transform into destructive invaders causing hundreds of millions in damages, and other domestic animals that return to the wild, such as feral pigs and cats, create similar challenges. “Preventing the introduction of invasive species is the most effective strategy for mitigating their impacts, and we hope our findings serve as valuable evidence for assessing future invasion risks,” concludes Dr. Carneiro.
