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Subject: search.filters.subject.410202 Biosecurity science and invasive species ecology

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    Translating biosecurity world-making : thinking with Mycoplasma bovis in Aotearoa : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Resource and Environmental Planning at Massey University, Manawatū, Aotearoa
    (Massey University, 2023-12-12) McDonald, Deidre Ann
    Aotearoa has one of the strictest biosecurity networks in the world and, at the same time, enacts one of the world’s most export-driven agricultural economies. It was into these dual assemblages that Mycoplasma bovis (M. bovis) first emerged, in July 2017, causing the (then) Biosecurity Minister to declare that M. bovis was Aotearoa’s ‘single biggest biosecurity event’. Consistent with this problematisation, and in a world-first manoeuvre, the government and farming industry bodies decided to try to eradicate the bacteria. This thesis tells the story of that eradication attempt and of M. bovis’ own attempt to fight back. This more-than-human research follows the network translation attempts of five key actors involved with M. bovis’ world-making. These are the eradicators themselves, the scientists enrolled in the programme, the farmers who were impacted by M. bovis (and by the eradicators), the cows who hosted the bacteria and M. bovis, the smallest living organism known to self-replicate. Together these network actors have enacted realities that are significant for the future of farming and biosecurity in Aotearoa. At the time of writing, the eradicators have almost succeeded in protecting and stabilising farming by Othering M. bovis from the network. In doing so, however, the eradicators have reterritorialised a pasture-based farming assemblage that is inherently fragile. Farming’s continual need for complex biological mobilities itself creates the need for ongoing biosecurity practices. Yet, as this thesis will show, these on-farm biosecurity practices are fundamentally incompatible with farming ontologies. There is a precarious misalignment between these two assemblages, each of which are vital for Aotearoa’s economic security. As to M. bovis’ bacterial world-making, this seems to be irrelevant to the human actors, despite their collective interest in non-human health. As a spokesperson for this M. bovis assemblage, I have tried to expose a series of ontological worlds. In doing so, my aim is to create a conceptual space for reimagining farming and biosecurity in Aotearoa.
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    Plant invasion down under : exploring the below-ground impact of invasive plant species and their biological control on soil properties and invertebrate communities in the Central Plateau of New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Ecology, Massey University, Palmerston North, New Zealand
    (Massey University, 2023) Pearson, Benjamin Michael
    With the increase in global trade and environmental disturbances, plant invasion continues to be one of the greatest threats to native ecosystems. The Central Plateau of New Zealand is of particular interest as it is home to several invasive plant species and biological control agents of these plants. Previous research has focused on the plant community responses of above-ground arthropods to plant invasions, but to my knowledge, no research has investigated soil properties and soil fauna communities at an individual plant level and compared these beneath native and invasive plants. Globally, information on post-release impacts of biological control agents on the below-ground communities and ecological processes is lacking, although we know that organisms such as foliar herbivores can impact the soil ecosystem indirectly, with consequences for control and subsequent recovery. This research aims to fill in this gap by investigating: 1) the soil properties and soil fauna communities associated with two native plant species (Leptospermum scoparium – mānuka, and Chionochloa rubra – red tussock) and two invasive species (Calluna vulgaris – heather and Cytisus scoparius – broom), and 2) how soil properties and soil fauna communities change under heather (C. vulgaris) plants at three stages of biocontrol agent (heather beetle) attack (prior, during and following the attack). In chapter 2, I sampled the soil physicochemical properties and macrofauna communities of two native and two invasive plant species. Rather than finding a difference between native and invasive plants as expected, I found a high degree of similarity between manuka and broom, and between red tussock and heather. This result highlighted the need to understand both the invasive and displaced vegetation when identifying impacts of invasion. In chapter 3, I sampled the soil ecosystem under heather plants before, during, and after feeding by the heather beetle. As expected, I found that the soil properties under heather differed before and during heather beetle attack. Unexpectedly, I found no difference in soil properties under heather before and after control by heather beetle. I also found that Collembola (springtails) and Oligochaeta (earthworms) were more abundant after heather beetle attack. Interestingly, Thysanoptera (thrips) abundances were highest prior to heather beetle attack, which could potentially have important consequences for biocontrol efficacy. These results provide some novel insights into the soil ecosystem responses to plant invasion, and the potential soil impacts post-biocontrol release, while highlighting the need for future research into a variety of plant species and control agents.
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    Aspects of the biology and control of old man's beard (Clematis vitalba) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2023) Jarvis-Lowry, Brenda
    Old man’s beard (Clematis vitalba) is an increasingly problematic liana in New Zealand, but the factors that contribute to its invasiveness are not fully understood. The work in this thesis investigated elements of old man’s beard seed biology and ecology, seedling establishment, and vegetative reproduction that were unclear or unknown. The findings point to a reproductive diversification strategy that contributes to old man’s beard’s success as an invasive plant, due in part to dual dispersal mechanisms (by wind and water), dual seed banks (aerial and soil), dual seed dormancies (physiological and morphological), and dual reproductive modes (seeds and vegetative spread). Summary of findings regarding the biology • The aerial seed bank is transient: half of all achenes tagged and monitored were dispersed via anemochory during complete dormancy in autumn, and all but 5% of the remainder were gone by early spring. • The likelihood of secondary water dispersal is high, as seeds tolerated up to 6 weeks of immersion, germinated readily in water, and produced seedlings that remained robust, if removed from water within the 6-week period. • Pre-chilling was found to be unnecessary for germination, even for seeds that had not undergone a full winter of after-ripening: although it increased the speed at which seeds incubated at constant temperatures germinated, it did not promote total germination as successfully as a fluctuating temperature regime without pre-chilling. • Seeds collected off the vine and tested for germination over a 2-year period were fully physiologically dormant until completely senesced. Thereafter, dormancy declined during winter, and seeds were largely non-dormant by early spring. However, morphological dormancy did not change until seeds were exposed for several days to suitable germination conditions. Fewer than 72% of seeds were ultimately viable. • The soil seed bank was confirmed to be relatively small but persists at least for two years. Seeds in the soil experience the same cyclic physiological dormancy changes as those in the aerial seed bank, though can also enter a secondary dormancy when appropriate germination conditions are not met. • Seedlings were not able to survive competition exerted by established perennial grass cover unless the cover was very sparse. However, seedlings that survived began producing multiple, elongating stems within six months of emergence. • Vegetative growth produces an extensive network of creeping stems on the ground. Also, two-node woody stem fragments from both creeping and climbing stems are capable of rooting and growing vigorously as individual, clonal plants. Current management of old man’s beard infestations necessarily involves chemical control. The efficacy of two types of herbicide control was also assessed. As a precision technique for climbing vines that avoids non-target damage, the basal bark method with triclopyr in oil provides highly effective chemical control of individual stems, with >95% mortality. The cut stem method, using a 45% glyphosate gel formulation was less effective (55% mortality). For creeping stems, triclopyr alone and a triclopyr/picloram/aminopyralid mixture were effective herbicide sprays that preserved grass cover. Favouring a dense grass cover can help suppress subsequent establishment of old man’s beard by seed. Management should also consider that waterways are potential conduits of propagule spread, and that mechanical fragmentation of stems serves to produce more individuals, due to regeneration.
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    The flax weevils of Mana Island : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Ecology at Massey University, Manawatu, New Zealand
    (Massey University, 2022) Brockelsby, William David
    In 2004 and 2006 flightless endemic flax weevils (Anagotus fairburni) were deliberately translocated to Mana Island, New Zealand, as part of the island’s restoration plan. The flax weevil population grew exponentially and by 2018 the weevils were dispersing and had destroyed large areas of their host plant, flax (Phormium spp.), on which threatened bird and lizard species on Mana Island rely for both habitat and food. Little is documented about flax weevil ecology, so it wasn’t immediately obvious why the flax weevil population was growing beyond the ability of the flax to sustain them. Investigations by Colin Miskelly into possible natural enemies of the flax weevil led to the discovery of a strain of the entomopathogenic fungi Beauveria pseudobassiana, naturally occurring on the island that was highly virulent to flax weevil larvae. This native pathogen was prevalent at the flax weevil release site, but uncommon further down the island, which led to the hypothesis that the flax weevil was able to disperse ahead of its natural enemy on the island. We decided to investigate the feasibility of deliberately spreading B. pseudobassiana ahead of the flax weevils, to protect flax plants from collapse and death. In August 2018 a trial site was established in the centre of the island well ahead of known flax weevil sites and 80 mature flax plants were individually marked. A fauna monitoring programme was put in place to understand the flax plant animal community before and after any experimental changes at the site. An irrigation system was designed and installed to deliver supplementary water to some flax plants, to test whether access to water during the crucial dry summer months was a critical variable for survival of flax plants. In March 2020 marked flax plants were treated with a solution of the virulent B. pseudobassiana strain, or a control mixture, both delivered via water the base of the plant. These plants were then stressed by the deliberate introduction of 1600 flax weevils. Numerous novel observations on flax weevil ecology and behaviour were made throughout the duration of the flax plant trial. Flax weevils were found to go through 6 to 7 instars as larvae in the soil, were mobile at the trial site as adults, and could walk long distances from their flax release sites over time. An alternative feeding plant was observed for adult weevils, which were found to feed on the leaves of Muehlenbeckia complexa. The trial release of B. pseudobassiana failed to protect most flax plants at the experimental site, with 35 out of 43 marked plants now (2022) in a state of heavy collapse or death. We attribute this failure to an insufficient dosage rate, although it is possible that release timing or environmental conditions might also have led to an unsuccessful release. Possible future ecological scenarios for flax weevil on Mana Island are discussed.
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    Amphibian disease risks and the anthropogenic dispersal of invasive Litoria species : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Albany, New Zealand
    (Massey University, 2021) Laycock, Jennifer
    The scope of this research is to provide a broad outline of the interaction between anthropogenic disease spread, risk of an invasive amphibian species establishing into the New Zealand environs, and prevalence of amphibian chytrid in wild introduced amphibian populations. The objective of this overview is to identify risk pathways that could threaten New Zealand’s four endemic Leiopelma species of frogs. Worldwide amphibian populations are in decline with an estimated 32.5% of amphibians globally threatened (IUCN 2008). New Zealand’s four endemic amphibians Leiopelma spp. are high on the ICUN list of critically endangered animals, further, two of the three introduced tree frogs (Litoria spp..) are listed endangered and vulnerable in their native home. Disease has been one factor implicated in the worldwide amphibian decline in particular the two diseases Chytridiomycosis and Ranavirus. Although Chytridiomycosis has had the most profound effect on the decline of amphibian species. The spread of such diseases is, at least in part, human-mediated through media such as the bait trade, food industry, and possibly the pet trade. To date, there have been no reports of Ranavirus in New Zealand amphibians. Conversely, amphibians chytrid fungus is widespread and has been implicated in the decline of the endemic Leiopelma archeyi. This makes amphibian chytrid an ideal disease to model disease transmission with particular reference to the anthropogenic movement of amphibians. The two main goals of this Ph.D. were to investigate specific anthropogenic mediated risks of spreading disease using the pathogen Batrachochytrium dendrobatidis (Bd), which is responsible for amphibian chytrid fungus, as a modality to model this. Included in this will be the enquiry into how Bd entered New Zealand and how it spread so quickly via the movement of Litoria spp.. Furthermore, to look at invasive amphibian species incursion risks by evaluating previous border seizures. Currently, it is unknown how the amphibian chytrid entered New Zealand and whether New Zealand’s borders are a high-risk entry pathway for amphibian disease. Examining the anthropogenic dispersal of Litoria in New Zealand and developing systems that reduce the risk of introducing disease into naive populations is an important role in ensuring the long-term survival of New Zealand’s endangered Leiopelma spp. frogs. The presence of Bd in New Zealand has been recorded but the prevalence of the pathogen in populations is unknown. Identifying the prevalence of infection within populations will provide insight into how populations of Litoria spp. are surviving Bd infection. Furthermore, this Ph.D. project will assess the risk of invasive exotic amphibians entering New Zealand and becoming naturalised. Education is one of the important areas that will greatly help the plight of New Zealand’s frogs. For education to be successful it needs to be targeted, therefore assessing risk areas of amphibian disease is imperative. Furthermore, understanding the public’s knowledge of frogs in New Zealand will further help in the development of resource material and targeting the main groups where education is needed. Key findings of this research are that the three species of Litoria frogs are moved around New Zealand in large numbers via the pet trade. The spread of amphibian chytrid has most likely been so rapid due to the frequency and volume of tadpoles and frogs being bought and sold. The pet trade thereby effectively and inadvertently is a major means of the unregulated translocation of Litoria amphibians throughout New Zealand. Results of this research also show there is a gap in the knowledge about amphibians in areas of husbandry, disease, species identification, and legal responsibilities in the ownership and containment of amphibians in New Zealand. Additionally, the introduction of a new disease is more likely to occur than the risk of an invasive species becoming established. Finally, the wild populations of Litoria frogs were surviving with a high prevalence of amphibian chytrid fungus in two of the three study sites in this research, the third site which had the presence of a reservoir species had low numbers of frogs present.
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    Volatile organic compounds emitted by invasive and native plant species under invasion scenarios and their potential ecological roles : a thesis presented in partial fulfilment of the requirement for the degree of Doctor of Philosophy in Ecology at Massey University, Palmerston North, New Zealand
    (Massey University, 2020) Effah, Evans
    Climate change, human migration, and global trade favour the spread of plant species beyond their natural ranges. Many of these plants become invasive, posing a risk to the persistence and survival of native species and the ecosystems they invade. In New Zealand, the European woody shrub Calluna vulgaris (heather) is the most widespread invasive weed on the Central Plateau of North Island. Like most exotic invasive plants, the chemical behaviour (i.e. chemical production and chemical mediated interactions) of heather in its invaded habitat is poorly understood. Moreover, despite the struggles of native plants to endure the stress induced by exotic weeds, no study has documented the chemical behaviour of native plant species in plant invasion scenarios. Volatile organic compounds (VOCs) are secondary plant metabolites that play a vital role in plant communication with other organisms and are highly responsive to biotic and abiotic stress. Therefore, measuring VOC emissions during plant invasion could provide valuable information about plant responses to the changing environment and their potential impacts on other community members. This thesis aimed to investigate VOCs emitted by the invasive weed heather and a New Zealand native plant Leptospermum scoparium (mānuka) under field conditions, while determining the environmental factors regulating their emissions and exploring their potential ecological impacts under lab and field conditions. Results from the field trials on the Central North Plateau showed variations in the volatile profiles of heather and mānuka growing at different sites, with both plants emitting lower amounts of VOCs at sites where other exotic invasive plants were present. This reduction in VOC emissions was mostly due to indirect changes in environmental factors, like soil properties, which were driven by the invasive weeds heather and Cytisus scoparius (Scotch broom; henceforth broom). This thesis also documents the chemical responses of heather to two major stresses encountered in New Zealand; 1) elevated solar ultraviolet radiation (UV) and 2) damage caused by its introduced specialist herbivore and biocontrol agent Lochmaea suturalis (heather beetle). Results from these trials demonstrate that high UV radiation reduced the volatile emissions of some compounds (mainly terpenoids) and that the impacts of herbivory by heather beetle on VOC emission depended on the developmental stage of the herbivore, plant phenology, and season. The ability of VOCs emitted from heather and broom to affect the germination and growth of mānuka was also tested in the lab, while the impact on arthropod communities were investigated at sites on the Central North Plateau. The results suggest that VOCs produced by invasive plants may have phytotoxic effects toward mānuka and may alter arthropod community structure. This thesis highlights the complexity of plant chemical communication under invasion scenarios and invites further exploration of the interactions between exotic invasive plants and native species to broaden our understanding of invasion ecology to support weed management, biocontrol, and conservation efforts.
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    Assessing the sustainability of anticoagulant-based rodent control for wildlife conservation in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Conservation Biology at Massey University, Palmerston North, New Zealand
    (Massey University, 2019) Sran, Suman Preet Kaur
    Brodifacoum is used extensively to control invasive rodent pest populations in New Zealand. However, there are major concerns regarding non-target poisoning due to brodifacoum, its high persistence and risk of emergence of resistance in targeted rodents. In the present study, I assessed brodifacoum resistance in ship rats and house mice using blood-clotting response (BCR) tests. Mature ship rats of both sexes were live trapped from Akatarawa forest, an area of no known anticoagulant use history in Wellington. A ranging study was performed whereby healthy ship rats were administered increasing doses of brodifacoum to calculate the effective dose, which in ship rats is considered to be the dose giving a 3.6-fold increase in blood-clotting time (this proportional increase is referred to as the International Normalised Ratio, or INR). An unexpectedly high effective dose of 2.9 and 3.8 mg/kg was calculated for male and female ship rats respectively. The calculated effective dose was used to access brodifacoum susceptibility in ship rats captured from nine areas of known brodifacoum use history in the Wellington region and Palmerston North. A total of 54 ship rats were successfully tested, and there was a significant decrease in INR with increasing number of years of brodifacoum use in an area. Despite this evidence of anticoagulant resistance revealed by BCR tests, no mutations conferring anticoagulant resistance were found in VKORC1 gene sequences in tested ship rats. This suggests that resistance may be caused by other pathways. Similarly, BCR tests were performed in house mice using the effective dose from published literature, i.e. 0.52 mg/kg for males and 0.46 mg/kg for females. Twenty out of 26 house mice assessed were found to be resistant to administered dose of brodifacoum, meaning the INR was >5. However, no relationship was observed between the INR value and the number of years of brodifacoum use in an area. Seven of the tested mice were found to have a non-synonymous mutation, Tyr139Cys in exon 3 of the VKORC1 gene. The house mouse individuals carrying this mutation are known to be fully resistance to all first-generation anticoagulants and a second-generation anticoagulant, bromadiolone, but only minor resistance is known to occur towards more potent second-generation anticoagulants. At present, only technical resistance to brodifacoum has been reported in ship rats and house mice, and brodifacoum may still be used effectively to control these rodent populations. However, continual use of brodifacoum may encourage further resistance. Effective long-term control of anticoagulant-resistant populations can only be achieved by use of alternative non- anticoagulant rodenticides.