UNSW Canberra

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  • (2021) Mijangos Araujo, Luis
    Genetic differentiation is a vital aspect of population genetics and is a direct consequence of evolutionary forces acting on genetic diversity. By interpreting patterns of genetic differentiation, we can detect, infer and estimate the extent to which natural selection, genetic drift and gene flow affect genetic diversity. In this thesis, estimation of genetic differentiation is used as a tool to answer the following questions, three mainly theoretical, and the other an applied study on platypus conservation. 1. Can a form of linked selection termed associative overdominance (AOD) explain lower levels of genetic differentiation between populations (FST), and higher heterozygosity, than expected under neutrality in experimental populations (Drosophila melanogaster) and in a feral population (Bos taurus)? 2. Under which circumstances does AOD affect FST and heterozygosity? 3. Can AOD be detected in natural populations? 4. Do dams restrict gene flow among platypus groups? AOD is triggered by the occurrence of recessive deleterious mutations that are physically linked and form haplotypes when recombination events are scarce, as in small populations. When haplotypes within an individual contain recessive deleterious mutations at different positions, a heterozygote for two different haplotypes is fitter than either one of the homozygotes. As a result, heterozygosity is higher, and FST lower than expected under neutrality. Here, using feral, experimental and computer- simulated populations, it is demonstrated how AOD might be prevalent in small populations, and a framework for predicting and detecting AOD is provided. The extent to which dams disrupt gene flow among platypus populations is investigated by using four rivers regulated by dams and three unregulated rivers. It was found that: genetic differentiation is significantly correlated with the number of generations since the dams were built; populations and individuals separated by dams are genetically more different than otherwise; and areas of high genetic differentiation coincide with the location of dams. It is suggested that dams jeopardise the long-term viability of platypus populations.