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Ecology, management and conservation in natural and modified habitats
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RESEARCH ARTICLE
Contents Vol 37(2)

Defining spatial genetic structure and management units for vulnerable koala (Phascolarctos cinereus) populations in the Sydney region, Australia

Tristan Lee A D , Kyall R. Zenger B , Robert L. Close C , Marilyn Jones A and David N. Phalen A
+ Author Affiliations
- Author Affiliations

A Wildlife Health and Conservation Centre, Faculty of Veterinary Science, The University of Sydney, NSW 2570, Australia.

B School of Marine & Tropical Biology, James Cook University, Townsville, Qld 4811, Australia.

C School of Biomedical and Health Sciences, University of Western Sydney, NSW 2560, Australia.

D Corresponding author. Email: t.lee@usyd.edu.au

Wildlife Research 37(2) 156-165 https://doi.org/10.1071/WR09134
Submitted: 1 October 2009  Accepted: 10 February 2010   Published: 16 April 2010

Abstract

Context. Mammal populations around the world are increasingly threatened with population fragmentation because of loss of habitat or barriers to gene flow. The investigation of koala populations in the Sydney region not only provides valuable information about this vulnerable species, but also serves as a model for other species that have suffered major rapid declines in population size, and are now recovering in fragmented habitat. The peri-urban study region allows investigation of the impact of landscape features such as major roads and housing developments on koala gene flow.

Aims. Animals originating from four geographic sampling areas around Sydney, New South Wales, Australia, were examined to determine population structure and gene flow and to identify barriers to gene flow and management units.

Methods. The present study examined 12 microsatellite loci and used Bayesian assignment methods and genic frequency analysis methods to identify demographically separate populations and barriers to gene flow between those populations.

Key results. Three discrete populations were resolved, with all displaying moderate to high levels of genetic differentiation among them (θ = 0.141–0.224). The allelic richness and heterozygosity of the Blue Mountains population (A = 6.46, HO = 0.66) is comparable to the highest diversity found in any koala population previously investigated. However, considerably lower genetic diversity was found in the Campbelltown population (A = 3.17, HO = 0.49), which also displayed evidence of a recent population bottleneck (effective population size estimated at 16–21).

Conclusions. Animals separated by a military reserve were identified as one population, suggesting that the reserve maintains gene flow within this population. By contrast, strong differentiation of two geographically close populations separated by several potential barriers to gene flow suggested these land-use features pose barriers to gene flow.

Implications. Implications of these findings for management of koala populations in the Greater Sydney region are discussed. In particular, the need to carefully consider the future of a military reserve is highlighted, along with possible solutions to allow gene flow across the proposed barrier regions. Because these are demographically separate populations, specific management plans tailored to the needs of each population will need to be formulated.

Additional keywords: gene flow, genetic diversity, koala, microsatellites, population structure.


Acknowledgements

Thanks go to all who assisted in the collection of samples, especially Melissa So, Lynn Bowden, Wendy and Michael Fairs, Steven Ward, Kieran Griffin, Mariette Ennik, Sharon Andronicos, members of the NSW Wildlife Information Rescue and Education Service (WIRES), staff at NSW National Parks and Wildlife Service, the Macarthur Advertiser, NPA Macarthur and the many members of the community who alerted us to koala sightings. We acknowledge funding from the Wildlife Health and Conservation Centre, The University of Sydney and The University of Western Sydney. We also thank the referees for their help in improving the paper.


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