Analysis unlocks secrets and techniques of rodents’ rat race to new lands — ScienceDaily

New research from the Australian National University (ANU) has mapped the DNA of more than 150 species of native rodents from across Australia, New Guinea and the Melanesian Islands, painting a clearer picture of how they are related to one another and how they will eventually spread across the Pacific.

The lead author Dr. Emily Roycroft said native rodents are a fascinating but often underestimated evolutionary group.

“Australia and New Guinea have over 150 species that are found nowhere else in the world, such as the rakali – or ‘water rat’ – which often swims around Canberra’s lakes,” said Dr. Roycroft.

“So far, we know very little about the evolution and origins of native rodents, particularly those in New Guinea.”

The team used a new approach to extract DNA from museum specimens up to 180 years old, including many extinct and elusive species.

“A specimen of the Guadalcanal rat from the Solomon Islands dates back to the 1880s and the species has not been seen since. It is listed as critically endangered and is very likely already extinct. We were curious to revisit these ancient specimens using modern technology,” said Dr. Roycroft.

Research shows that mountain building in New Guinea five million years ago was the trigger for the spread of native rodents in the region. The expansion of New Guinea opened up new environments for rodents to adapt to, including through improved connectivity with Australia, the Solomon Islands, and the Maluku Islands.

“We have known for some time that Australia’s native rodents originated in Asia and entered our region via the water – possibly a lone pregnant animal floating on a piece of driftwood. Now we have a precise timeline for it and an explanation for why we’re seeing so many species today,” said Dr Roycroft.

“Our study shows that native rodents are excellent at colonizing new areas. When they first arrived in Australia, they adapted to many new environments – including the arid desert.

according to dr Roycroft, additional information on the history of native rodents could prove crucial to the future of these species.

“Native rodents have deep intrinsic value in our ecosystems. They are ecosystem engineers; they aerate the soil by digging and foraging, and they help disperse seeds and fungal spores,” she said.

“They also play a role in food webs as an important source of native predators and in turn feed on plants, fungi and small animals.

“But they also have the highest rate of extinction of any Australian mammal group, due to extreme habitat loss and introduced predators. Losing even one native species can upset the balance in an ecosystem.

“Understanding how our native rodents evolved and adapted will help us conserve the ones we still have.”

The research was supported by Bioplatforms Australia through the Australian Government’s National Collaborative Research Infrastructure Strategy (NCRIS).

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