5 days ago
Outback discovery prompts theory of new sub-species: 'We know they exist'
Researchers have discovered an isolated group of possums living in Western Australia are part of a locally extinct population that once roamed the Red Centre. Separated from other possums, the group found around the Pilbara and the Midwest have become smaller overall, grown larger ears, developed a thinner tail, and become less furry to cope with the heat.
Lead researcher and Edith Cowan University PhD candidate, Shelby Middleton, theorised they could one day evolve into their own sub-species because they are now isolated. 'They are showing differences in the way they look, and will not be mixing with other populations because they don't have any gene flow anymore,' she told Yahoo News Australia.
Although these possums appear visually different, the population is actually the same subspecies that lives on the east coast and South Australia. This means its ancestors once had a range that extended over 3,000km across the continent to Melbourne and Sydney.
Sadly, the population has become isolated because the introduction of cats and foxes by European settlers killed them off in central Australia. It's hard to imagine how different Australia looked 250 years ago, when the centre would have been teeming with life. Another small marsupial, the greater bilby, once covered 80 per cent of the continent, but it is now threatened with extinction.
Previously, it had been thought that the population of brushtails in the Pilbara and Midwest was the same subspecies as those in Perth and the southwest. But they had simply evolved to appear visually similar because they lived in a similar environment.
But after Middleton and her team partnered with the Western Australian Museum and Department of Biodiversity, they linked its genetic material to the east coast subspecies. This was done using preserved museum specimens and roadkill collected by locals in the regions being studied.
Prior to the research, there was only one other subspecies known to exist in Western Australia, the smaller northern brushtail, which is found in the Kimberley.
Trichosurus vulpecula arnhemensis exists in the Kimberley and the Top End.
Trichosurus vulpecula hypoleucus exists in southwest WA, Barrow Island, and Broome.
Trichosurus vulpecula vulpecula exists in Pilbara, Midwest, the east coast and South Australia,
While populations of brushtails in the east remain stable, some in the west are gradually declining.
The Pilbara is continuing to develop industrially, with the federal government approving a new fertiliser plant for the region last year, and an extension of Woodside's North-West Shelf fossil fuel extraction program last week.
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Traditionally, new projects have had to evaluate their impact on threatened species, but not those believed to be abundant. They are also probably overlooked at sites when construction is being undertaken.
'We need to increase awareness so mining companies take more notice of brushtail possums when they do see them,' Middleton said.
'We've got a lot to learn about this population in the Pilbara and Midwest because it's been previously overlooked. We don't completely know their range. We know they exist in some small populations, but outside of towns we don't know where they are.'
The research is published in the Zoological Journal of the Linnean Society.
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