Introduced in the late 19th century to establish a fur trade, possums went on to become serious pests, damaging many forest ecosystems and killing native birds and some insects.
Introduced in the late 19th century to establish a fur trade, possums went on to become serious pests, damaging many forest ecosystems and killing native birds and some insects.
Kiwi scientists have reconstructed the entire genetic jigsaw of the brushtail possum, in a breakthrough that could help control the pesky marsupial here and conserve it across the Tasman.
The just-published results of their five-year-long study reveal a trove of new insights into the species, such as where and when their genes are expressed - and surprising details about their population diversity, reproduction and origins.
The study’s lead author, Associate Professor Tim Hore of Otago University’s Department of Anatomy, described possums as “a fascinating animal that is loved in one country and a cause of concern in another”.
“They are hunted in Aotearoa New Zealand for their fur and controlled for conservation, but treasured and protected in Australia,” he said.
“Having their full genetic code is important for both countries, as efforts to manage their respective populations are being held back by the lack of this knowledge.”
Introduced in the late 19th century to establish a fur trade, possums went on to become serious pests, damaging many forest ecosystems and killing native birds and some insects.
As carriers of bovine tuberculosis, they also threaten biosecurity and trade.
One of three key species of the Predator Free 2050 mission’s hit list, possums now cost an estimated $150 million each year for the Government to control.
In contrast, they remain a cultural and ecological treasure in their native range, where southern Aboriginal tribes use their skins for cloaks, depicting images and stories on them throughout their lives.
“In New Zealand, where the possum is a harmful introduced species, we can use the information to help guide control and eradication strategies, by tracking and monitoring target populations on the basis of their genes,” Hore said.
“But in the same way, our work will also be useful for its conservation in Australia, where it is a valued native species.”
A potential novel way to improve possum population management has also been revealed by DNA sequencing, based on chemical communication genes the researchers have discovered.
“Possums are nocturnal, so non-visual means of communication are really important,” Hore said.
“We uncovered possum genes responsible for carrying scent in urine, and found that although they are silenced in newborns, they are switched on in adults, particularly males.
“Molecules produced from these genes could be used to lure possums towards a trap or keep them away from pest-free areas.”
Otago University geneticist Associate Professor Tim Hore.
Professor Dan Tompkins, science director at the study’s co-funder Predator Free 2050 Limited, was excited about the results due to the research and development pathways they opened up.
“Through the Predator Free 2050 mission, we are driving to eradicate possums – along with rats and stoats – from the whole of Aotearoa to protect native biodiversity, and we are always on the lookout for more targeted, efficient and humane ways of getting the job done,” he said.
“Deciphering their genetic code provides us with an invaluable new knowledge base that underpins and enables exploration of a range of better approaches to do just that, from possum-species toxins to fertility control, and the exciting new ideas leveraging scent communication proposed here.”
Researchers also uncovered new details regarding the establishment of possums in New Zealand from Australian populations.
Study co-first author Dr Donna Bond, also of Otago’s Department of Anatomy, said possums from the study were collected from Otago Peninsula and other sites near Dunedin, but were genetic hybrids tracing back to discrete populations in Tasmania and the Australian mainland.
“Although the possums introduced in the 19th century were low in numbers, perhaps a few hundred, because they are mixed up from at least four different Australian populations, the New Zealand animals we tested had more genetic diversity than those from Australia.”
Hore said the study, published in the major scientific journal Nature Communications, marked the first time the species had ever been genomically sequenced.
Compared with the human genome, containing 23 pairs of chromosomes and more than 63,000 genes, the possum’s genome was slightly larger, Hore said.
“In some ways, genome sequences are becoming quite routine now – although this one proved quite special because of how well the genome was assembled,” Hore said.
“Now that we’ve got the possum’s genetic code, in the long-term, there’s always the possibility of doing things to alter their genes to control their fertility.”
While some scientists and conservation advocates have said New Zealand’s bold 2050 bid could be impossible without game-changing genetic solutions.
Hore himself has been exploring a new method that involves targeting and transplanting immature sex cells of possum pouch young, rather than embryonic cells, before they develop into eggs or sperm.
But there was no indication that genetic tools – which were far from developed and haven’t found wide support from either the public or governments to date - would be unleashed against our pests any time soon.
Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.
