For playing a leading role in ground breaking threatened species recovery work cesar Director, Dr Andrew Weeks, is part of a group of scientists that have been nominated for the prestigious Eureka prize in 2018.
The mountain pygmy possum in dire straits
Just imagine you are one of the few surviving members of your community.
There are less than 20 of your kind living in a small area together, unable to leave due to lack of shelter and the risk of predation. You stay put and your population continues to dwindle.
The mountain pygmy possum (Burramys parvus), which is one of Australia’s most endangered marsupials, is restricted in range to the alpine regions of south eastern Australia. The situation described above was the reality for one population of the mountain pygmy possum only 13 years ago at the popular tourist destination of Mt Buller Alpine Resort.
This southern population was only discovered in 1996 and is genetically isolated from all other populations found in the central and northern alpine areas of Victoria and New South Wales. Within 10 years of discovery, the Mt Buller population went through a dramatic demographic and genetic collapse. By 2005 there were less than 20 individuals known to be present in the population. Genetic variation had reduced by over 70%.
Habitat destruction and fragmentation, due to resort developments, as well as predation by feral invasive predators were key drivers of the population collapse. By 2005, models had predicted that the Mt Buller mountain pygmy possum would be extinct within 10 years.
Feral predator control programs and efforts to restore habitat and reconnect the Mt Buller population with other mountain pygmy possums, led by Mt Buller Mt Stirling Resort Management, had resulted in limited success. These activities addressed the environmental issues, but these possums remained in a genetic slump due to severe inbreeding – the population had remained completely isolated for over 20,000 years.
Animal populations typically contain a lot of genetic variation, which is essential if populations are to continually adapt and evolve in response to disease and other environmental threats, while also avoiding the negative consequences of inbreeding. To increase health and fertility this population would need an injection of new (and different) DNA.
Bringing the mountain pygmy possum back from the brink
The challenge to solve this problem was taken up by cesar researchers, Dr Andrew Weeks and Anthony van Rooyen, and collaborators from the University of Melbourne, La Trobe University, The University of NSW and Mt Buller Mt Stirling Resort Management (Dean Heinze, Louise Perrin, Dr Jakub Stoklosa, Prof Ary A. Hoffmann, Ian Mansergh, and Tom Kelly). The answer that the team came up with was genetic translocation – the mixing of genetically distinct populations of the same species.
It was an ambitious plan that involved translocating six males from a genetically healthy population at Mt Higginbotham in the central region to the Mt Buller population during the peak breeding period in spring of 2011. Another group of males from a population at Timms Spur in the central highlands was also translocated to Mt Buller in 2014.
Outbreeding depression was a real risk from using such an approach, and a major reason why genetic rescue of Australian threatened species had not been used previously. Outbreeding depression can occur when two genetically distinct individuals of the same species produce offspring that are less adapted to the environment (less fit) than their parents. Potential outbreeding depression would need to be closely monitored throughout the rescue program.
The results that these researchers had hoped to achieve could soon be seen in the capture-recapture data over the following seasons. The fitness advantage was large, with offspring estimated to be at least twice as fit as their Mt Buller counterparts, and this advantage persisted through to the next generation. More specifically, offspring from Mt Higginbotham males and Mt Buller females were bigger, more fertile, and the females had longer lifespans than offspring of Mt Buller males and females. Outbreeding depression was not evident – this possum population had regained genetic diversity, and ultimately had gained more tools in its genetic tool kit to combat environmental and biological threats.
Prior to this success with the Mt Buller mountain pygmy possum, genetic rescue had never been applied in Australia to a threatened species. However, threatened populations of many other animals are in a similar situation as the Mt Buller population of the mountain pygmy possum. This work has provided a template for other rescue efforts dealing with a genetic bottleneck, and since the success of this program, cesar has begun applying its learnings in genetic rescue to other threatened marsupial populations, such as eastern barred bandicoots and brush-tailed rock-wallabies, as well as threatened fish species including the dwarf galaxias and Yarra pygmy perch.
The success of this initiative, and the diligent and excellent work by all involved has now been recognised by the Australian Museum Eureka prize panel, which is presented annually and rewards excellence in the fields of research and innovation, leadership, science engagement, and school science. Dr Andrew Weeks and collaborators are finalists for the prize, with the winner to be announced in late August at a gala award dinner at the Sydney Town Hall.