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(c) Quintin Lau
My Phd focussed on the study of immunology and immunogenetics of Koalas.
My supervisor was Associate Professor Damien Higgins who also leads the Koala Health Hub
(c) Jorge Cham
Written by Quintin Lau and David Phalen, Koala Health Hub, The Faculty of Veterinary Science, The University of Sydney
What is genetic diversity?
Genes are the building blocks of all living organisms, and is the basic unit for heredity. Genes are made up of DNA, which has instructions for making proteins. Genetic diversity is the total genetic makeup of a species, and is the most fundamental of the three levels of biodiversity (genetic, species, ecosystem).
Source: igbiologyy.blogspot.com
Why is genetic diversity important?
Genetic diversity is important for a species or population to survive and adapt; especially to changing habitat or new diseases. If genetic diversity is low in a population, individuals become genetically similar and this increases inbreeding. There are 2 types of genetic diversity that scientists study: (1) neutral genes, which are more informative about population history, and (2) adaptive genes, which are related to the fitness of a species/individual and how they are affected by natural selection.
Koala brief history and current genetic diversity.
Koala populations were quite widespread before European settlement, but crashed in the late 19th century as a result of many human factors (hunting, habitat loss) and disease. Shortly after, translocation programs were established; mainly in offshore islands in Victoria, where a small number of koalas were the founding population in each island (this founding of a population with only a few animals is called a genetic bottleneck because it restricts the diversity of genes that that make it through to the new population). Many koalas from island populations were later returned back to the mainland Victoria and most of these populations have recovered even to the point of over-abundance in some areas (Martin and Handasyde 1999). As a consequence, the genetic diversity of koalas from Central to Western Victoria and South Australia is low (both neutral and adaptive genes). Koala populations in Victoria from South Gippsland east have a much greater genetic diversity, making them an important focus for conservation efforts and management (Lee et al 2011; Lau et al 2014).
Koalas were hunted extensively following European settlement.
A truck piled with koala skins during hunting period, Queensland, 1927 (John Oxley Library, State Library of Queensland)
In northern New South Wales and Queensland (‘north’), many koala populations are currently declining and are fragmented due to land development (development of roads and residential areas result in koala habitats being cleared and separated from each other). Overall, these koala populations have higher genetic diversity (both neutral and adaptive genes) than populations from Victoria, as they did not experience severe bottlenecks in the past (e.g. translocations on islands) and many populations in the north are genetically distinct from each other (the genes in one population are quite different to genes in a different population) (Houlden et al 1996; Lau et al 2014). Due to a decline in koala numbers in the north, populations in NSW and Queensland were listed as ‘vulnerable’ in early 2012 under the Australian federal Environment Protection and Biodiversity Conservation (EPBC) Act 1999.
What can we learn for the future?
Koala populations in southern Australia are considered to be thriving, but have a low genetic diversity. This means that these populations are potentially at greater risk to changes to the environment or new diseases (they cannot adapt as well due to their genetic makeup). It is important to continue monitoring and protecting these koalas. The history of the koala’s translocation programs show that current and future conservation programs of koalas and any other species must consider maintaining high genetic diversity for continual survival of the species.
Source: Lisa Green
Koala populations in the ‘north’ seem to be genetically diverse, although these populations are declining. Each small fragmented population that is lost is a potential loss of diversity forever, so it is important to continue to protect the koalas and their habitat to avoid loss of genetic diversity and maintain healthy, resilient koala populations.
Houlden BA, England PR, Taylor AC, Greville WD, Sherwin WB (1996) Low genetic variability of the koala Phascolarctos cinereus in south-eastern Australia following a severe population bottleneck. Mol Ecol 5:269-81
Lau Q, Jaratlerdsiri W, Griffith JE, Gongora J, Higgins DP (2014) MHC class II diversity of koala (Phascolarctos cinereus) populations across their range. Heredity
Lee T, Zenger KR, Close RL, Phalen DN (2011) Genetic analysis reveals a distinct and highly diverse koala (Phascolarctos cinereus) population in South Gippsland, Victoria, Australia. Aust Mammal 34:68-74
Martin R, Handasyde KA (1999) The Koala: Natural history, conservation and management. University of New South Wales Press Ltd, Sydney
(c) Quintin Lau
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