Port Stephens koalas face limited gene flow leaving population vulnerable to disease, climate change: research

STUDY: An inquiry into a small sample of DNA from Port Stephens koalas suggests that isolated populations in the area are experiencing limited gene flow leaving them vulnerable to disease and climate change. Picture: Marina Neil

STUDY: An inquiry into a small sample of DNA from Port Stephens koalas suggests that isolated populations in the area are experiencing limited gene flow leaving them vulnerable to disease and climate change. Picture: Marina Neil

A small koala DNA study conducted at Port Stephens appears to suggest that koala populations in the area are experiencing increasingly limited gene flow between isolated clusters.

Conservationist groups who ordered and participate in the study fear that the loss of genetic diversity in the animals could mean future generations are unable to fight off new disease, or to adapt to climate change.

The small-sample research was commissioned by the World Wide Fund for Nature as part of its 'Koala Forever' plan to double the eastern Australian population by 2050, and conducted by researchers from Federation University in Sydney who analysed scat samples from 39 koalas in the Port Stephens area belonging to two main population clusters there.

Researchers indicated that further studies of larger sample sizes would be needed to shore up results, but initial findings suggested that gene flow was most limited in a peninsula population of Koalas near Tomaree and Tilligerry, and that limitations were beginning to appear in an inland population at Ferodale and Balickera on the Pacific Highway.

ISOLATED: Researchers identified two isolated koala clusters, which genetic analysis indicated were once connected.

ISOLATED: Researchers identified two isolated koala clusters, which genetic analysis indicated were once connected.

As the koala's natural habitat has receded, and become fragmented by suburban development, road building, and industry expansion, koalas have found it increasingly difficult to migrate and diversified breeding has become limited, ecologist attached to the study have said.

"Now koalas are confined to smaller patches of forest surrounded by inhospitable habitat such as houses, buildings, roads and farmland, it's difficult for koalas to disperse and migrate, as they are programmed to do, and often proves fatal," koala conservation ecologist Olivia Woosnam, who co-authored the study report, said.

CANINE COOPERATION: Researchers used specialist detection dogs to collect faeces samples from 39 individual koalas in the Port Stephens area for the study.

CANINE COOPERATION: Researchers used specialist detection dogs to collect faeces samples from 39 individual koalas in the Port Stephens area for the study.

The WWF and OWAD Environment - a koala ecology group which used specialist detection dogs to collect faeces samples for the study - have used the results to call for habitat preservation at Port Stephens, and for well-designed infrastructure to allow koalas to cross the Pacific Highway and promote gene flow, particularly between the Ferodale and Balickera populations, which they say would benefit populations on both sides of the road.

"Habitat fragmentation, which impedes gene flow, is a major problem for koalas and other species. That's why a major focus of Koalas Forever is to protect existing habitat, regenerate cleared forests, and to plant tree corridors to reconnect isolated populations," Darren Grover, of WWF-Australia, said.

Genetic data analysed as part of the inquiry showed the peninsula and inland clusters were once connected. However, the report noted that peninsula koalas "are now significantly different from those sampled further inland suggesting that gene flow between peninsula and inland koalas has been restricted over recent generations".

STUDY: An inquiry into a small sample of DNA from Port Stephens koalas suggests that isolated populations in the area are experiencing limited gene flow leaving them vulnerable to disease and climate change. Picture: Marina Neil

STUDY: An inquiry into a small sample of DNA from Port Stephens koalas suggests that isolated populations in the area are experiencing limited gene flow leaving them vulnerable to disease and climate change. Picture: Marina Neil

In October last year, Federal Environment Minister Sussan Ley approved the controversial extension of the Brandy Hill quarry, despite strong opposition from residents who feared the project would clear up to 52 hectares of koala habitat.

Ms Ley said strict new conditions had been attached to the project, including the establishment of a 74-hectare koala habitat corridor to support the local populations.

Members of the Save Port Stephens Koalas campaign, which attracted celebrity endorsements to opposing the quarry expansion, feared that after losing a quarter of the local koala population to devastating the summer bushfires of 2019, the surviving natural habitat would be crucial to the future of the survival of the local population.

Dive deeper: Port Stephens koalas and the Brandy Hill Quarry expansion:

This story Port Stephens koalas threatened by limited gene flow: DNA study first appeared on Newcastle Herald.