Blog

The truth comes out in the end

By: Dr Mark Eldridge, Category: AMRI, Date: 09 May 2017

Genetic analysis of scats (faecal pellets) from a remnant rock-wallaby colony has revealed an unexpected evolutionary history.

Brush-tailed Rock-wallaby (Petrogale penicillata) scats at Mt Kaputar National Park.

Brush-tailed Rock-wallaby (Petrogale penicillata) scats at Mt Kaputar National Park.
Photographer: Mark Eldridge © Australian Museum

The first genetic analysis of the tiny remnant population of Brush-tailed Rock-wallabies (Petrogale penicillata) from Mt Kaputar has revealed a close relationship to populations from the Warrumbungles and central NSW rather than populations on the adjacent Northern Tablelands. This finding increases the importance of the Mt Kaputar population to the long-term survival of the species.

The Brush-tailed Rock-wallaby (BTRW) is now extinct west of the watershed of the Great Dividing Range, apart from remnant populations in the Warrumbungles and at Mt Kaputar. Previous genetic analysis has identified deep genetic subdivisions within BTRWs, which have been used to guide management. However, the Mt Kaputar population, near Narrabri in northwestern NSW, was not included in these studies, because the single remaining colony is tiny (less than 10 individuals) and inhabits a large complex rock pile where access and trapping is difficult. 

However, with advances in technology DNA sequence data can often be obtained from feacal pellets (scats). In September 2015, with local NPWS staff, we were fortunate to visit the BTRW colony at Mt Kaputar. Although we didn’t see any rock-wallabies we did locate and collect a series of lovely fresh scats.

Back in the lab at the Australian Museum Research Institute, we were able to obtain mitochondrial DNA (mtDNA) sequence data from several scats and so determine the population’s genetic affinities. Our analyses showed the Mt Kaputar BTRWs were most closely related to those from the Warrumbungles (~160 km to the southwest) and other populations south of the Hunter River in central NSW. Surprisingly, the Mt Kaputar population was not closely related to populations on the adjacent Northern Tablelands, despite the Nandewar Range apparently providing habitat connectivity and the historic presence of intervening BTRW populations. The similarity of the Mt Kaputar and Warrumbungles BTRW populations indicates relatively recent historical gene flow between these sites despite the lack of suitable habitat or historic populations between them. Clearly we still have a lot to learn about BTW behaviour and dispersal.

But what we do know is that the genetically similar, remnant Mt Kaputar and Warrumbungles BTRW populations are highly threatened and are the only BTRW still persisting in semi-arid conditions. This makes them of particular value to the long-term survival of the species in the face of anthropogenic climate change and their conservation should be a priority.

Dr Mark Eldridge, Principal Research Scientist, AMRI

This research was generously funded by an Australian Biodiversity Conservation Grant from Mrs Mary Holt and the late Dr John Holt.