<p>Biological invasions are one of the major causes of biodiversity decline on the planet. The key driver of the global movement of invasive species is international trade. As a response to trade driven invasive species risk, international and domestic regulations have been promulgated with the goal of managing the spread and impact of non-native species. My aims in this thesis were twofold. First, my goal was to review a subset of international and domestic regulations with a view to commenting on their fitness for purpose and suggesting potential improvements. Second, I used the example of non-native and invasive Hymenoptera, as well as their pathogens, to illustrate the risks posed by invasive species and gaps in their management. In order to assess international and domestic regulations, I reviewed the World Trade Organization’s (WTO) Agreement on Sanitary and Phytosanitary Measures, as well as associated disputes. I argue that the WTO’s regulatory system does, for the most part, allow domestic regulators to manage invasive species risk as they see fit. Subsequently, the focus of the thesis narrows to investigate New Zealand’s pre- and post-border regime managing invasive species. I argue that New Zealand’s pre-border approach represents international best practice, but the post-border management of species is fragmented. The power to manage invasive species has been delegated to sub-national and regional bodies, which typically approach invasive species management in different ways. This variation has led to regulatory inconsistencies in pests managed and funding allocated. There appears to be a substantial lack of planning in some spaces, such as the risk of aquatic invasions. I make recommendations to ameliorate these inconsistencies. My second aim involved the study of non-native and invasive Hymenoptera in New Zealand, as well as the pathogens they carry, in order to illustrate the risks posed by invasive species and gaps in their management. I show that the globally widespread invasive Argentine ant (Linepithema humile) may play a role in the pathogen dynamics and mortality of honey bee hives where the species occur sympatrically. Hives in the presence of Argentine ants suffered significantly higher mortality rates relative to hives without ants and always had higher levels of a honey bee pathogen Deformed wing virus. I demonstrate that honey bee pathogens are found in a range of invasive Hymenoptera in New Zealand. I amplify entire genomes of the honey bee virus Kashmir bee virus (KBV) from three species of non-native or invasive Hymenoptera (Argentine ants, common wasps and honey bees). I show that there is KBV strain variability within and between regions, but more between regions. Further, I demonstrate the result that as sampled KBV sequence length increases, so too does sampled diversity. These results highlight how ‘an’ invasive species is typically not alone: they carry a range of diseases that are almost always not considered in international and regional management plans. Patterns of non-native Hymenoptera carrying honey bee diseases were not restricted to New Zealand. I used mitochondrial DNA to find the likely origin of invasive populations of the globally distributed invasive German wasp. I demonstrate that German wasps show reduced genetic diversity in the invaded range compared to the native range. Populations in the introduced range are likely to have arrived from different source populations. In some regions there were likely multiple introductions. Other regions are genetically homogenous and represent potential areas for use of gene drive technologies. All four different honey bee pathogens assayed for were found in German wasp populations worldwide. These results highlight how the introduction of one exotic species likely brings a range of pathogens. This example of pathogens in Hymenoptera is likely to be true for nearly all non-native introductions. Many of the impacts of biological invasions, such as predation and competition, are relatively obvious and are frequently studied. However some, such as the impact of pathogens, are unseen and poorly understood. Legal regulation is often a post-hoc response implemented once a problem has already arisen. At a global level regulatory regimes operate relatively effectively. As the focus becomes more granular, such as the case of pathogens of Hymenoptera, fewer controls exists. This thesis helps to reduce uncertainty in this area as well as makes recommendations as to how these risks may be managed.</p>
Expanding the Propagule Pressure Concept to Understand the Impact of Biological Invasions
