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have been introduced, over-browsing by the localised expansion of populations is a significant management issue (Melzer et al. 2000; Phillips 1990).

22. Genetic structure and diversity
In all species there is a strong interplay between a species' genetic diversity and their behaviour, ecology, reproductive biology, and other life history characteristics. Our knowledge of Koala genetics has increased in the past five years with the development of new genomic technologies. These genetic investigations are important for decision making in Koala management, such as translocations and disease management.
Genetic diversity is important for a species to maintain its adaptive potential, that is, the more diversity a species has at functionally important genes the better. The Koala genome is slightly larger than the human genome (3.5Gb v 3.2Gb) and contains approximately 20,000 genes (Johnson et al. 2018). Genes are located across the genome, and the areas between the genes are often called neutral regions. Neutral regions mutate faster than functional gene regions, and so conservation geneticists typically measure differences in these neutral regions to determine how different populations are to each other. Conserved functional genes tend to mutate at a slower rate, so the genetic differences within these conserved genes tends to be less than what we see in neutral regions. If functional genes are under selective pressure (due to some external factor) there can be differences within these genes, meaning different populations can have different diversity within these genes. Immune genes are an example of the types of genes that can have different diversity depending on the population they come from.
Measuring genetic diversity and understanding diversity within genes is a rapidly evolving field. A range of different genetic methods have been used over the past 20 years to describe genetic diversity in Koalas with benefits and limitations to the different methods (Table 5). Understanding the benefits and limitations of particular methods, allows us to better understand the current genetic status of Koala populations.
Table 5. Methods used to describe genetic diversity in the Koala, their benefits and limitations
Genetic marker type                                                                                                                              Benefits                                                                                                                    Limitations
Microsatellite markers – 6 consistent markers (Houlden et al. 1996); other markers developed but not consistent across studies                   Cheap and reproducible                                                                                                      Only represent small portions of the genome
                                                                                                                                                 6 markers developed by Houlden et al. 1996 have been used by 14 of the 22 genetic studies published between 1996 and 2019   Tend to only represent neutral regions
                                                                                                                                                                                                                                                                             Markers need to be consistent across studies to be comparable
Reduced representation sequencing – 2 methods ddRAD (3,060 SNPs in Koalas; Kjeldsen et al. 2016) or DARTseq (4,606 SNPs; Kjeldsen et al. 2019)*  Produces thousands of single-nucleotide polymorphisms (SNPs) representing genome-wide diversity                             ddRAD and DARTseq methods are not comparable; method needs