Details

Autor(en) / Beteiligte

• Backus, Gregory Alan

Titel

Population Dynamics Models of Invasive Rodent Eradication with Gene Drive Technology

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2017

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• Invasive rodents have caused considerable damage to island ecosystems, contributing to the extinction of several rare endemic species. To protect these unique ecosystems, rodents have been eradicated from hundreds of islands throughout the world. Unfortunately, eradication usually involves the heavy application of chemical toxicants that can harm and kill many non-target species. Genetic engineering could provide an alternative, species-specific eradication technique. One example would involve engineering a house mouse (Mus musculus) to carry a genetic construct that would cause a majority of its offspring to be male, many of which would be sterile. Releasing these genetically engineered mice to interbreed with an invasive population would reduce the number of fertile female mice in that population until no more remain. I build and analyze a series of mathematical models to explore the population dynamics and population genetics of eradicating an invasive island-rodent population using the previously described genetic construct. First, I use a differential equation model that describes the spread of this suppressing gene drive through a density-dependent population. With this model, I highlight conditions under which the gene drive would eradicate the population. Particularly, if mice carrying the gene drive have a substantial survival advantage over their wild-type counterparts, the gene drive could spread through and eradicate a population with a single release. More likely, gene drive mice would have a fitness disadvantage, and eradication would require repeated releases of the gene drive into the population. I also use this model to show that increasing the speed and efficiency of eradication comes at the expense of a more disruptive transient impact on the surrounding ecosystem. Next, I adjust the previous model to allow for the potential of heritable female mate choice. I find that preferential mating in favor of wild-type males could act as a form of gene drive resistance as it becomes more frequent in response to the gene drive. On an island, this resistance could be countered with higher gene drive release rates, which could force the population to extinction before preferential mating has the opportunity to evolve. Alternatively, preferential mating could instead act in favor of gene drive males. Even when gene drive males have a survival cost, strong preferential mating in their favor could allow for the long-term persistence of a gene drive or even result in eradication. Lastly, I construct and analyze a stochastic eradication model where mice are separated into a collection of discrete patches. Within this context, I simulate eradication in a variety of conditions by varying dispersal rates, number of patches, and the topology of patch connections. A balanced repeated release of the gene drive into every patch is most successful, but it would likely be infeasible without full knowledge of the population structure. If gene drives are not able to be released throughout the full spatial extent of the population, eradication is still possible, though less effective. The minimum number of areas necessary to release the gene drive depends on dispersal and patch topology.