The Theory of Island Biogeography on the Hawaiki Archipelago

This thesis addresses MacArthur and Wilson‟s Theory of Island Biogeography (1967) on a set of islands around the north-east coast of the North Island of New Zealand. The flora species lists from these islands were obtained from both published and unpublished island surveys whilst Geographical Information Systems (GIS) techniques were utilised in order to calculate the physical geography of islands. These islands were an ideal study site for such research because they display natural gradients in both physical geography as well as native and exotic species richness. The literature on the Theory of Island Biogeography has yet to comprehensively understand the differences between the patterns of exotic richness and native richness. Furthermore, the importance of studies on exotics species is increasingly relevant given the negative effect they have had on native communities worldwide. The results of my research illustrated that there were similar species-area and species-isolation relationships between exotic and native species. These two relationships were also consistent with what is expected under classical island biogeography principles. Interestingly however, I found that distance from the mainland had a stronger negative effect on exotics species. There were a significantly lower proportion of exotics with increasing isolation. This result has applicable outcomes for conservation management on the Hawaiki archipelago. I suggested that weeding effort focus on larger islands and in particular the islands closer to the mainland. Globally, the biogeographical patterns of exotic species are still poorly examined. With insights from this study and other similar research the Theory of Island Biogeography may be an informative approach to dealing with the ominous threat of exotic species.