Conservation genetics of Australian quolls

Abstract

As carnivorous marsupials, quolls are keystone species crucial to ecosystem health. Although opportunistic and adaptable, anthropogenic disturbance has led to severe population declines. In response, captive breeding and translocation programs were implemented in an attempt to mitigate extinction risks.

This thesis provides genetic (microsatellite) data to guide management of the four Australian quoll species. Parameters of interest to conservation were examined. Differences between translocated and endemic, island and mainland, and central and peripheral populations were also investigated. In addition, analysis of paternity was performed in a spotted-tailed quoll population.

Despite severe range contraction, western quolls (chuditch) have higher genetic variation than other Australian quoll species. Conversely, genetic variation is lowest in eastern quolls, but also in northern quolls restricted to islands. Evidence of founder effects were detected in translocated island, but not in translocated mainland populations, emphasizing that greater losses in genetic diversity occur on islands compared to mainland populations due to isolation from sources of gene flow.

In accordance with the ‘central-peripheral’ hypothesis, genetic variation is greater in central than in peripheral eastern quoll populations. By contrast, significant differences in diversity were not detected among any of the sampled chuditch populations, which is likely to be a result of the translocations. Similar analyses could not be conducted for northern and spotted-tailed quolls, because the sampled populations were not extensively distributed across these species’ geographical ranges.

Although genetic differentiation is significant among populations within each quoll species, moderate levels of admixture were detected, suggesting that gene flow is playing a role in maintaining connectedness among populations. However, given that eastern quolls are less mobile than other Australian quoll species, they may be more susceptible to anthropogenic disturbance.

Finally, multiple paternity was detected in a spotted-tailed quoll population and appears to be a strategy that has evolved to maintain genetic variation and reduce inbreeding within populations.

These data provide invaluable information to guide and improve the conservation of the four Australian quoll species. Ongoing management of these threatened species, such as population monitoring, supplementations and translocations, will help ensure that quolls remain as keystone species in the Australian environment.