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Genetic diversity and gene flow among southeastern Queensland koalas (Phascolarctos cinereus)

Fowler, EV, Houlden, BA, Hoeben, P & Timms, P 2000, Molecular Ecology, vol. 9, pp. 155-164.

The extraction of DNA among southeastern Queensland koalas showed significant genetic diversity between most populations indicating that these populations are most likely structured along matrilines, in which individuals are considered to belong to the same descent group as their mother. 

  Data for this study were collected from ten study sites located within a 100km radius of Brisbane and at least 20km apart from one another. Due to low numbers of koalas at most sites, only five locations were suitable for analyses at which ten or more individuals were present. To test for unique mitochondrial DNA (mtDNA) haplotypes, blood samples from a total of 106 koalas across these sites were collected. A total genomic DNA extraction method was then carried out and mtDNA sequences amplified using polymerase chain reaction (PCR). The analysis of within-species genetic variation was conducted using heteroduplex analysis (HDA) combined with temperature gradient gel electrophoresis (TGGE). The results revealed eight distinct mtDNA control-region haplotypes with varying degrees of genetic inter-relatedness, which may suggest historical population bottlenecks or undocumented translocation of koalas between populations. Within distinct koala populations, haplotypes ranged from one to five with a diversity of 0.379  0.016 and nucleotide diversity of 0.22  0.001%. This nucleotide diversity averaged at 0.09  0.001% between populations ranging from 0.00 to 0.14%. The study also detected the maternal inheritance of mtDNA which, combined with the significant genetic heterogeneity revealed, suggests that the koala populations studied are structured along matrilines in which females do not disperse from natal sites to the same extent as male koalas.

  This study successfully quantified the genetic diversity and gene flow within and between select populations of koalas in southeastern Queensland. The genetic diversity and limited haplotypes in the Gold Coast may suggest a historical bottleneck population possibly due to environmental events, while divergent haplotypes around Moreton Bay may indicate the translocation of some koalas. To elaborate on these results, more data is needed about a wider range and number of koala populations to reveal a clear phylogeographical pattern among these haplotypes.

  The findings of this study contribute to our understanding of how historical events have contributed to the genetic diversity of southeastern Queensland koala populations. Further studies like this one will expand the present findings and contribute to conservation management strategies that can maintain or enhance genetic diversity in wild populations.

 

Summarised by Robyn Boldy

 

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