A new study mapped the DNA of more than 150 native rodents from Australia, New Guinea and the melanesian islands. It paints a clearer picture of their relationship and how they eventually spread across the Pacific. Lead author Dr Emily Roycroft of the Australian National University said native rodents are a fascinating, but often underappreciated, evolutionary group.
Dr Roycroft said: "There are over 150 species in Australia and New Guinea that are not found anywhere else in the world, such as Rakali – or 'water rat' that is often seen around the lakes of Canberra. ”
"Until now, we know very little about the evolution and origin of native rodents, especially species in New Guinea."
The team used a new method to obtain DNA from museum specimens up to 180 years old, including many extinct and elusive species.
"A Guadalcanal mouse from the Solomon Islands could have dated back to the 1880s, after which the species has never been seen again. It is listed as critically endangered and is likely to be extinct. Dr Roycroft said: "We are curious to revisit these old specimens using modern technology. ”
The study shows that the formation of mountains in New Guinea 5 million years ago was the trigger for the spread of native rodents in the region. The expansion of New Guinea opened up new adaptations for rodents, including by increasing connections to Australia, the Solomon Islands and the Maluku Islands.
"We know that native rodents in Australia originated in Asia and reached our region by water – probably a pregnant animal floating over a piece of driftwood. Now we have an accurate timeline and explain why we see so many species today," said Dr. Roycroft.
"Our study shows that native rodents are outstanding in the colonization of new areas. When they first arrived in Australia, they adapted to many new environments – including arid deserts. ”
Dr Roycroft said having additional information about the history of native rodents could prove critical to the future of these species. "Native rodents have a deep intrinsic value in our ecosystem. They are the engineers of the ecosystem; They ventilate the soil by burrowing and foraging, and they help disperse seeds and fungal spores," she said.
"They also play a role in the food web and are a great source of native predators, which in turn feed on plants, fungi and small animals themselves."
"But they also have the highest rate of extinction of any mammal population in Australia due to extreme habitat loss and introduced predators." If we lose even one native species, it upsets the balance of the ecosystem. ”
"Understanding how our native rodents evolved and adapted will help us protect those species we have left."
The study has been published in the journal Contemporary Biology.