Abstract:
The threat imposed by invasive species and difficulties associated with control and management places more impetus on trying to prevent their introduction. The identification of introduction pathways is a vital component towards this goal. In this thesis I studied the use of genetic markers to retrospectively investigate the pathway of origin of the invasive Argentine ant (Linepithema humile) and the red imported fire ant (Solenopsis invicta) into New Zealand. I sampled from a mitochondrial gene in both species. No genetic variation was found within the Argentine ant and genetic variation was present in the red imported fire ant. In order to identify their likely introduction pathways, I used two forms of alternative genetic analysis, each of which had particular uses for each species. For Argentine ants the genetic sequence, when compared to a global database, matched that from an Australian population. The red imported fire ant genetic data matched two populations located in Argentina. Both species had an origin in the native range from North-central or North-eastern Argentina. My approach can easily be duplicated for other organisms and the methodology can be more widely applied to help aid further efforts to identify the routes of transmission for other invasive species and allow us to efficiently direct our biosecurity monitoring effort. In addition I investigated the colony structure of both species in New Zealand. Colony structure and behaviour can have important impacts on the dispersal mode as well as success of populations. Behavioral and genetic data were gathered for the Argentine ant, but only genetic data for the red imported fire ant. The Argentine ant was found to be unicolonial throughout New Zealand. From the three incursions observed in New Zealand, the red imported fire ant both polygyne and monogyne nests were present. These findings help determine the proper management strategies that should be implemented to deal with invasive populations present in New Zealand.
