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    Social dynamics in natural populations of Dictyostelium discoideum : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Evolution at Massey University, Auckland, New Zealand
    (Massey University, 2024-12-05) Broersma-Stam, Cathleen
    Evolutionary theory predicts that selection should favour individuals who act in their self-interest, resulting in widespread selfish behaviour. Nonetheless, cooperative behaviours that provide benefits to others are common in nature. Over the past 50 years, evolutionary biologists have established a framework to explain how cooperation can be maintained despite the threat of selfish individuals who fail to cooperate but benefit from the cooperation of others. This framework has mostly been built around social behaviours in animal societies such as social insects. However, the more recent discoveries of social behaviours in microbes, analogous to those observed in animals, allow us to examine the generality and importance of proposed mechanisms that limit selfishness in non-animal societies. The social amoeba Dictyostelium discoideum has become an established model system in social evolution studies. Upon starvation, genetically unrelated cells can co-aggregate to form a ‘chimeric’ fruiting body in which some cells altruistically die to form a supportive stalk while others become viable spores. Theory and empirical work have shown that altruistic stalk formation can select for cheaters: genotypes that preferentially allocate cells to the spores and exploit stalk formation by their social partner. This finding has led to a considerable number of studies that demonstrated proof-of-principle for mechanisms that both promote and limit cheating in this organism. In contrast, few studies have examined whether cheating is widespread in nature, nor assessed the importance of the previously identified mechanisms that may limit this behaviour. In this thesis, I aimed to bridge the gap between the laboratory and a more natural situation. Using a diverse collection of natural strains of D. discoideum, I investigated the frequency and intensity of cheating among natural strains, the mechanisms that limit this behaviour, and the potential evolutionary consequences of interactions between cheaters and cooperators. Overall, this thesis will contribute to the growing body of work that examines how cooperative behaviours can be maintained in non-animal societies.
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    Rare, tropical and subtropical fishes in Aotearoa New Zealand : monitoring occurrences and predicting impacts : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Biological Sciences at Massey University, Albany, New Zealand
    (Massey University, 2022) Littlewood, Katie
    Species redistribution due to climate change is occurring four times faster in the ocean than on land. As global temperatures rise, equatorial regions are becoming increasingly inhospitable, driving tropical and subtropical species to track favourable conditions poleward or at deeper depths, to keep within their thermal tolerances. The expectation is that tropical regions will become more inhospitable and temperate regions will become increasingly tropicalised as the ability for warmer water species to persist increases. Tracking range-shifts in the ocean is a difficult, time consuming and often expensive task, as many marine species are highly mobile, cryptic and wide ranging. As such, our understanding of climate induced distributional changes and the threats they pose is far from complete. Nevertheless, the increase of tropical and subtropical species in temperate regions has the potential to alter biodiversity, displace endemic species and cause significant shifts in ecosystem function. While Aotearoa New Zealand has remained relatively unimpacted by climate change to date, the frequency of tropical and subtropical arrivals will continue to increase as global climate change forces species to seek refuge in temperate regions. With a high level of endemism and a relatively depauperate ecosystem, the establishment of range-extending species in Aotearoa New Zealand has the potential to have negative impacts. This thesis contributes to the understanding of tropical, subtropical and rare marine fishes in Aotearoa New Zealand by highlighting the potential for citizen science as a means of monitoring occurrences, and through examining the morphology and ecological niches of arriving fishes to predict their potential impacts on Aotearoa New Zealand’s native and resident species. First, through structured questionnaires, I demonstrate that citizen scientists can provide reliable (83.33% of questionnaires) observations of tropical and subtropical fishes without the need for photographic equipment or post-hoc validation, thus providing more equitable opportunities for citizens to contribute to marine science and monitoring initiatives. Second, through analysing the broadscale trophic niche, habitat preference and morphology of marine fishes I reveal there is considerable niche overlap between arriving marine fishes and native resident marine fishes (74.37%) suggesting there is high potential for competition should arriving species establish and increase in abundance in Aotearoa New Zealand. Overall, my results highlight the need for proactive monitoring of arriving fishes, to limit the potential impacts on native and resident species and our marine ecosystems.
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    Investigating variation in the diet and foraging ecology of the long-finned pilot whale (Globicephala melas edwardii) in Aotearoa New Zealand waters: A thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Zoology at Massey University Albany, New Zealand
    (Massey University, 2023-12-20) Hinton, Bethany
    Knowledge of foraging ecology is essential to understanding how species interact with the ecosystem they inhabit. Foraging variation due to ontogenetic and/or anthropogenic factors can affect individual body condition, which could have implications for reproductive fitness and survivorship. Despite a high stranding frequency, limited knowledge is available on the foraging ecology of long-finned pilot whales (LFPWs; Globicephala melas edwardii) within New Zealand waters. To address these knowledge gaps, multiple methods of dietary analysis (stomach content analysis, n = 283; stable isotope analysis, n = 125; and fatty acid analysis, n = 15) were performed on samples collected from carcasses of LFPWs stranded along the New Zealand coast between 2009 and 2017. Six new taxa contributed to LFPW diet, including the first report of fish consumption for this population. Whilst arrow squid Nototodarus spp. was determined to be the most important prey, both ontogenetic and spatiotemporal variation were noted in prey consumption. Stomach content, stable isotope and fatty acid investigations all supported a preference for pelagic feeding. However, both stomach content and stable isotope investigations also documented occasional benthic/coastal foraging, especially for mature male LFPWs and in the year 2017. Biochemical dietary tracers examined in five of the top prey species to LFPW diet at Farewell Spit suggested that prey investigated were not chemically similar and/or at least one key prey species was missing from analysis. Initial insights gained from morphometric body condition measurements signalled that axillary girth may explain some variation in the proportion of saturated, polyunsaturated fatty acids and dietary fatty acid C20:1n9 in the inner layer of dorsal blubber, though sample sizes were small. Given the sustained reliance on arrow squid in the diet of this species, monitoring of overlap between regions of commercial fisheries and LFPW foraging in these waters, in part through continued support of long-term data sets, is recommended. Furthermore, the importance of accurate body condition measurements and their potential for use in welfare assessment and strandings situations is discussed. Recommendations for future research, include telemetry studies, further investigation of fatty acid and body condition biomarkers in LFPWs and prioritisation of analysis of LFPW dietary samples collected during the austral winter.
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    The foraging behaviour and range of little penguins (Eudyptula minor) at two neighbouring colonies : a thesis presented in partial fulfilment of the requirements of the degree of Master of Science in Conservation Biology at Massey University, New Zealand
    (Massey University, 2022) Elsom, Henry
    Differences between colonies in foraging behaviour have been reported for little penguin colonies in New Zealand and Australia. The differences between colonies are generally attributed to different environmental conditions at the colonies. However, no New Zealand study has compared the foraging behaviour of two neighbouring little penguin colonies that share the same marine environment. The current study compared the foraging behaviour of birds from two colonies in Oamaru, New Zealand, during the guard stage of the 2016 breeding season. These colonies were the Oamaru Blue Penguin Colony (OBPC) and the Oamaru Creek Penguin Refuge colony (Creek). These colonies are less than 1 km apart, so individuals have access to the same marine environment. Data loggers were used to assess at-sea behaviour and to determine the foraging range of little penguins at each colony. All recorded foraging trips during the guard stage were single day trips and which penguins departed from their colony early in the morning and return to their colony in the evening. There were no consistent differences between colonies in foraging and diving behaviours. The mean maximum distance from each colony was < 25 km. There was a difference between colonies in the mean duration of trips, with a longer mean trip duration for Creek colony birds than OBPC birds. The mean return time to the colony was later for Creek individuals. The mean foraging range per trip was greater for Creek individuals than for OBPC birds. This difference in mean values was attributed to a higher proportion of wide-ranging trips by Creek individuals. Practical limitations for the study meant that the sample sizes were smaller than those of some other studies. It is considered likely that if a larger sample size had been possible then the results would have shown no difference between colonies in the mean foraging range per trip during the guard stage in 2016. There were no differences between colonies in diving behaviour variables. The total foraging areas for individuals from each colony were compared between colonies to determine if there were distinct foraging areas for birds from each colony. Distinct foraging areas have been observed for neighbouring populations of conspecifics for many seabird species. However, the foraging areas for little penguins from the OBPC and Creek colony is overlapped and were not distinct. Distinct foraging areas for seabirds from neighbouring colonies is thought to be driven by intra-specific competition, so competition between colonies for foraging areas appears to have been low for Oamaru little penguins during the 2016 guard stage.
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    Habitat use by Tasman parakeets (Cyanoramphus cookii) and Crimson rosellas (Platycercus elegans) on Norfolk Island, South Pacific : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology, Massey University, New Zealand
    (Massey University, 2019) Simmonds, Serena Analeia
    Islands harbour a disproportionate amount of threatened vertebrate species and remain the focus of intense conservation research and management. Two important components of the ecological restoration of islands include revegetation and control of introduced animal species. The Tasman parakeet (Cyanoramphus cookii) endemic to Norfolk Island, is one of the rarest bird species in the South Pacific, with a long history of assisted conservation in particular during the breeding cycle. An introduced parrot, the crimson rosella (Platycercus elegans), is thought to compete strongly with Tasman parakeets for nesting and feeding resources, however, the degree of competition for feeding resources has not been quantified. No study has aimed at understanding the selection of available habitats by Tasman parakeets and crimson rosellas, or the relevance of restored vegetation patches for these species for foraging activities. In order to provide information to better manage a growing population of the Tasman parakeet within the Norfolk Island National Park, it is important to understand patterns of habitat use and key resources, as well as the degree of competition with the introduced crimson rosella. I studied the habitat use of Tasman parakeets and crimson rosellas during two seasons, autumn and spring 2017 by surveying 986 vegetation plots. I encountered a total of 80 woody plant species occurring on nine habitat types. The highest plant species richness was in forest edges (70 species), followed by remnant hardwood forest (43 species). The lowest plant species richness was on regenerating vegetation patches (26 species). Tasman parakeets and crimson rosellas used these habitats differently. In autumn and spring, Tasman parakeets preferred remnant hardwood forests (Manly Selectivity Index autumn: 0.50; Chi square 6.86, P < 0.001, n = 35; Manly Selectivity Index Spring: 0.32; Chi square 6.86, P < 0.001, n = 55). Crimson rosellas preferred forest edge in autumn (Manly Selectivity Index Autumn: 0.34; Chi square 24.51, P < 0.001, n = 69) and remnant hardwood in spring (Manly Selectivity Index Spring: 0.28; Chi square 4.56, P < 0.001, n = 130). In terms of feeding species, Tasman parakeets and Crimson rosellas exhibited a high degree of overlap in only one food type: ake ake (Dodonea viscosa) seeds and fruits. Opportunistic observations during summer, revealed a similar degree of overlap for consumption of seeds and pulp of red guava (Psidium cattleianum), although habitat preferences for summer or winter were not quantified in this study. I did not register a single instance of aggressive interactions between Tasman parakeets and crimson rosellas after nearly 300 hours of field observations. My results indicate that Tasman parakeets and crimson rosellas used the available habitats in the Norfolk Island National Park differently. In terms of foraging resources, Tasman parakeets and crimson rosellas do not appear to overlap greatly in food types or feeding species during autumn and spring. Future research should focus on the patterns of habitat use during summer and winter and the degree of competition for feeding resources during these seasons as well. While there has been evidence (prior to this research) of intense competition for nesting cavities between Tasman parakeets and crimson rosellas, my research reveals little inter-seasonal overlap in habitat use and feeding resource. From a management perspective, control of crimson rosellas in an around nest cavities of Tasman parakeets should be favoured over control on foraging areas. Nevertheless, crimson rosellas outnumber Tasman parakeets 3:1, and therefore my results need to be interpreted with caution as it is unclear whether foraging and habitat use patterns consistent with my research would be encountered in the future, as numbers of Tasman parakeets continue to increase.