This article comes from The Age, journalist is Bridie Smith, April 19, 2012
How distance made the possums grow fonder
POSSUM Researchers have intervened in an emergency move to deepen the gene pool of one of Australia’s rarest marsupials, the threatened Mountain Pygmy-possum. Studies showed as few as two or three males from the isolated Mt Buller population were successfully mating with females each year, contributing further to genetic depletion of the threatened species. However scientists from the DSE and Melb Uni have combined to ‘genetically rescue’ the Mt Buller population by removing six males from Mt Hotham and introducing them to the females on Mt Buller. They have since tested the results of this intervention – and this year found that half the offspring are hybrids (Dad from Mt Hotham, Mum from Mt Buller). It’s good news, as the hybrids are genetically more robust than pure Mt Buller animals.
THEY used to get along famously. So well that the Mount Buller mountain pygmy-possums and their Mount Hotham peers would regularly traverse the high country in search of a bit of alpine amore.
Then, 10,000 years ago, all that changed, as a warming planet saw their alpine habitat retreat uphill, leaving the Mount Buller possums effectively isolated on their mountain island.
The enforced isolation has been to their detriment, with the population shrinking to just 30 ”genetically impoverished” animals.
In recent years, the situation became so dire that as few as two or three Mount Buller males were successfully mating with females each year.
But intervention by a team of researchers – who are playing cupid and introducing the boys of Mount Hotham to the girls of Mount Buller – may have improved their plight.
Scientists from the Department of Sustainability and Environment and Melbourne University have combined with independent expert Dean Heinze to genetically rescue the Mount Buller population.
Last September they removed six males from Mount Hotham and introduced them to the females at Mount Buller.
The latest results of this intervention show that nine of the 16 juveniles captured in January were hybrid animals.
It is welcome news for the plight of the species that numbers about 1500 in the wild, as the hybrids are genetically more robust than the pure Mount Buller animals.
”They have lasted for over 10,000 years and then, in 1996, bingo, they reached a point of being so inbred that they couldn’t dig themselves out,” said DSE research scientist Ian Mansergh.
”It is why we had to step in. No matter how good the habitat was or how many foxes we killed, the genetics meant it was going to go down to nothing.”
Tests on the hybrid animals born in October last year showed they were four grams heavier than their pure peers. Dr Mansergh said the difference was significant, given the animals only weighed about 25 grams. ”That’s about 15 per cent heavier – and if you’re bigger, you’re stronger,” he said.
Andrew Weeks, from Melbourne University, said two hybrid offspring born in 2010 had also been found, meaning they had survived winter to reach breeding age.
It is the first time scientists have proved it is possible to breed mountain pygmy-possum hybrids in the wild, after Healesville Sanctuary successfully bred hybrids in captivity.
Dr Mansergh said this was an important milestone for the species which could be applied to other threatened and endangered species, including plants. He said it would prove particularly valuable as environmental conditions are altered under climate change.
Mr Heinze said the successful intervention meant it was unlikely more males would need to be introduced to the Mount Buller population in the immediate future. ”If nature takes the course we expect, there will be more hybrid pygmy-possums on Mount Buller in the coming years with a much brighter future,” he said.
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