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Thursday, 16 December 2021

Study reveals Mountain Pygmy-possum maintaining genetic diversity

A genomic study of Mountain Pygmy-possum populations in Victoria has shed new light on supporting their conservation and management. 

The study, commissioned by the North East Catchment Management Authority, and prepared by CESAR Australia, has used a next generation approach to analyse genetic samples collected from 13 Mountain Pygmy-possum populations in Victoria.  

The samples were collected during monitoring surveys between summer 2017-18 and autumn 2021 by Dean Heinze, a leading Mountain Pygmy-possum expert who’s been studying the species for more than two decades.

The new method determines spatial population structure and provides insights into the genetic health of populations, such as gene flow and inbreeding levels. 

The analyses indicate that although possum populations are highly fragmented, their genetic diversity is still moderate.

Fragmentation – when the small becomes smaller 

According to the results, populations fall into four main genetic groups or clusters:

  1. Mt Buller,
  2. across Mt Bogong/Timms Spur,
  3. Bogong High Plains, and
  4. across Mt Loch/Mt Higginbotham/Mt Little Higginbotham. 

While the fragmented groups are consistent with previous studies, this approach was able to take the analysis to a finer scale. The study has revealed further information on the level of connectivity within populations, providing increased resolution of the differences within each cluster. 

The results detected genetic differentiation between the Mt Loch East and Mt Loch North sites and the Mt Higginbotham East and Mt Higginbotham West sites. While Mt Higginbotham sites are partly separated by resort infrastructure, the habitat is relatively contiguous across Mt Loch.

The study findings suggest the current habitat has been ineffective at connecting these patches or that other barriers to movement may be at play, such as the presence of predators.  

The study highlights the fragmentation of Mountain Pygmy-possum populations at small spatial scales, which may pose an ongoing threat. It also highlights the importance to monitor these populations to inform timely management for species recovery. 

Success stories told by the genes  

Genetic rescue 

The study found the Mt Buller cluster to have the highest genetic diversity across all populations, but this finding is no coincidence. Before 2011, this was the most inbred Mountain Pygmy-possum population across the species’ entire range, which prompted agencies to act.

A genetic rescue took place by introducing males from other populations in 2010 and 2014, along with habitat and predator control programs, resulting in a turning point for the Mt Buller population from the lowest to the highest diversity across Victoria. 

Tunnels of love 

Another piece of good news revealed by the genetic analysis was the positive outcomes from more recent interventions, with the construction of the “tunnels of love”, completed in 2018.  

The possum tunnel was constructed to reconnect the Mt Little Higginbotham population, which had become separated by the Great Alpine Road. The study shows no significant genetic differentiation between the samples from either side of the road, indicating the tunnel successfully restored the gene flow between the two areas. 

The study was supported by the Australian Government’s Bushfire Recovery for Wildlife and their Habitat program. 

 

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