The Genetically Less Diverse Koalas

Photo source: koalas.org

# A species relies on genetic diversity to survive and low diversity usually indicates that there has been inbreeding due to a decrease in population size. By looking at historic mitochondrial DNA from museum samples, new research published in BioMed Central’s open access journal BMC Genetics has found that koalas (Phascolarctos cinereus) have had low genetic diversity for over 120 years.

# Koala populations had been very low due to Aboriginal hunting in the late 18th century and it was believed that the species would soon become extinct.

# But the hunting declined allowing the koala to become a common animal by the mid 1800s. 

# At this point in time koala fur became fashionable and the international fur trade decimated the population once more.

# The koala population was also hit by loss of their habitat to European settlement, and by devastating epidemic diseases such as Chlamydia. 

# Researchers from Germany, Denmark and the USA compared the mitochondrial DNA of modern koalas and 14 museum specimens from across the world. but there seemed to be not much diversity in between them. Each had only one of four different haplotypes(variations in the mtDNA hypervariable region).  

# The event which reduced the genetic diversity of koalas must have happened a long time ago, perhaps                                                               

   during the late Pleistocene  when the larger species of koala, P. stirtoni, became extinct.

What does this mean?

Low genetic diversity may mean that the species is less able to survive changes to its environment such as global warming, or competing for habitat with humans. The low diversity may also be responsible for the widespread inability of the koala to resist diseases such as Chlamydia and the newly discovered koala retrovirus.