Deﬁning spatial genetic structure and management units for vulnerable koala (Phascolarctos cinereus) populations in the Sydney region, Australia
Tristan LeeA,D, Kyall R. ZengerB, Robert L. CloseC, Marilyn JonesA and David N. PhalenA
AWildlife Health and Conservation Centre, Faculty of Veterinary Science, The University of Sydney, NSW 2570, Australia.
BSchool of Marine & Tropical Biology, James Cook University, Townsville, Qld 4811, Australia.
CSchool of Biomedical and Health Sciences, University of Western Sydney, NSW 2560, Australia.
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 infragmented habitat. The peri-urban study regional lows 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.Thepresentstudyexamined12microsatellitelociandusedBayesianassignmentmethodsandgenicfrequency 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 (q=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.