School of BioSciences - Theses
Permanent URI for this collection
Search Results
1 - 1 of 1
-
ItemTargeted gene flow for conservation: northern quolls and the invasive cane toad( 2018)Global biodiversity is declining at an unprecedented rate. Within declining populations, however, there are some individuals who are able to survive the threat. Unfortunately in many cases these adaptive traits are not common enough to prevent extinction, particularly when threats are rapid and severe. But by understanding how species respond to certain threats conservationists may be able to boost adaptive potential in threatened populations. Targeted gene flow is a novel conservation tool that involves moving individuals with relevant traits to areas where they could be beneficial for conservation. Although the implications are wide reaching, this idea is yet to be attempted on a wild population. In this thesis, I set out to test the feasibility of targeted gene flow as a conservation tool, using the endangered northern quoll (Dasyurus hallucatus) as a model species. Northern quolls have experienced dramatic declines since the introduction of the invasive cane toad (Rhinella marina) because the quolls unsuspectingly attack the toxic toads. There are, however, a small number of remnant quoll populations that have survived the toad invasion, seemingly because they do not attack toads. It is this potential “toad-smart” behaviour I hoped to harness using targeted gene flow. If it was possible to breed toad-smarts into still threatened areas of the northern quoll’s range, managers could boost adaptive potential and population survival. The first step was to understand how some individuals could survive alongside toads. In the preliminary chapters of this thesis, I examine toad-exposed northern quolls to see how they react to cane toads. I found that quolls from areas invaded by cane toads were indeed toad-smart – they didn’t attack toads. Using a common garden experiment, I then demonstrated this toad-smart behaviour had a heritable basis, meaning I could potentially breed the trait into threatened populations. The next step was to explore how best to implement targeted gene flow for quolls, including investigating any potential negative impacts. I used population modelling to explore the optimal timing and number of individuals introduced to maximise population survival whilst maintaining species-level genetic diversity. I then set up an experimental field trail, releasing both toad-smart and toad-naïve northern quolls onto a toad-infested island. Despite unforeseen circumstances that resulted in a dramatic reduction in population size, I was able to demonstrate no negative implications of targeted gene flow from the first stage of the experiment. This thesis shares the process of exploring a new conservation strategy, from initial conception to field trials. I provide evidence that targeted gene flow could reverse declines of threatened northern quoll populations – demonstrating a genetic basis for toad-smart behaviour, showing little evidence of outbreeding depression, and presenting the ideal management approach for implementing the tool in threatened populations. The resulting strategy is not limited to northern quolls, but instead has widespread applications for other threatened populations. Even the most endangered populations often have some individuals who are resistant to a threat. If conservations can understand and harness these adaptive traits, targeted gene flow could prove an invaluable tool for conserving threatened species.