Research@Lincoln
Research@Lincoln is an open access institutional repository collecting the research produced by Lincoln University staff and students. You may also be interested in Data@Lincoln or Lincoln University Living Heritage.
Students wishing to submit a thesis or dissertation should see the Depositing theses and dissertations guide.
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Item Metadata only Limiting grazing periods combined with proper housing can reduce nutrient losses from dairy systems(Springer Nature, 2022-12-08)Pasture-based and grass-fed branding are often associated with consumer perceptions of improved human health, environmental performance and animal welfare. Here, to examine the impacts of dairy production in detail, we contrasted global observational (n = 156) data for nitrogen and phosphorus losses from land by the duration of outdoor livestock grazing in confined, grazed and hybrid systems. Observational nitrogen losses for confined systems were lowest on a productivity—but not area—basis. No differences were noted for phosphorus losses between the systems. Modelling of the three dairy systems in New Zealand, the United States and the Netherlands yielded similar results. We found insufficient evidence that grazed dairy systems have lower nutrient losses than confined ones, but trade-offs exist between systems at farm scale. The use of a hybrid system may allow for uniform distribution of stored excreta, controlled dietary intake, high productivity and mitigation of animal welfare issues arising from climatic extremes.Item Restricted Variation in ovine KRTAP13-3 and its association with wool characteristics in Chinese Tan sheep(Multidisciplinary Digital Publishing Institute (MDPI), 2025-04-07)Understanding the genetic factors that influence wool quality is essential for enhancing wool quality and uniformity. This study investigated the KRTAP13-3 gene in Chinese Tan sheep, a breed known for its unique wool characteristics. We analysed 232 sheep and revealed five previously identified sequence variants of KRTAP13-3 and then modelled to ascertain whether there was any association between the nucleotide sequence variation and variation in mean fibre diameter (MFD), fibre diameter standard deviation (FDSD), coefficient of variation of fibre diameter (CVFD), and mean fibre curvature (MFC). Twelve genotypes were observed, with the five variants having frequencies that ranged from 64.0% to 1.1%. Among the four variants with frequencies above 5%, nucleotide sequence variation was associated with heterotypic hair fibre diameter variation. The most common variant (A) was linked to increased FDSD and CVFD, while two other variants (B and D) revealed trends towards being associated with decreased CVFD. No associations were found with variation in the fine wool fibres from the Tan sheep. This suggests that KRTAP13-3 plays a role in regulating heterotypic hair fibre diameter variability and that it could possibly be a gene marker for improving wool traits.Item Restricted Global and regional ecological boundaries explain abrupt spatial discontinuities in avian frugivory interactions(Springer Nature, 2022-11-14)Species interactions can propagate disturbances across space via direct and indirect effects, potentially connecting species at a global scale. However, ecological and biogeographic boundaries may mitigate this spread by demarcating the limits of ecological networks. We tested whether large-scale ecological boundaries (ecoregions and biomes) and human disturbance gradients increase dissimilarity among plant-frugivore networks, while accounting for background spatial and elevational gradients and differences in network sampling. We assessed network dissimilarity patterns over a broad spatial scale, using 196 quantitative avian frugivory networks (encompassing 1496 plant and 1004 bird species) distributed across 67 ecoregions, 11 biomes, and 6 continents. We show that dissimilarities in species and interaction composition, but not network structure, are greater across ecoregion and biome boundaries and along different levels of human disturbance. Our findings indicate that biogeographic boundaries delineate the world’s biodiversity of interactions and likely contribute to mitigating the propagation of disturbances at large spatial scales.Publication Open Access An investigation into the genetic forces shaping the LOP Locus of Pilosella piloselloides var praealta : A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Applied Science at Lincoln University(Lincoln University, 2024)Gametophytic Apomixis, a form of asexual reproduction that bypasses meiosis and fertilisation, enables plants to produce seeds that are genetically identical to the female parent. It is a potentially revolutionary technological advance for global food security, enabling accelerated plant breeding and seed production. There are three critical processes employed by gametophytic apomicts for clonal seed production. These are ‘Apomeiosis’ (the avoidance of meiosis), ‘Parthenogenesis’ (embryo formation without fertilisation) and Autonomous Endospermy (endosperm formation without fertilisation). In the model apomict, Pilosella piloselloides var. praealta, the asexual dominant allele at the LOP locus (LOP), has been identified as a critical element involved in the avoidance of fertilisation. Recently, LOP has been mapped to a 654kb region of the genome (Bicknell et al. 2023). This thesis builds on this discovery and the finding that the dominant PARTHENOGENESIS (PAR) gene, shown to drive spontaneous embryo formation in Taraxacum, is positioned at one end of the defined 645kb LOP allele (Underwood et al. 2022). This positioning poses a compelling question about the forces driving the structure of this allele: Is the structure of LOP due to genetic co-inheritance, requiring the two extreme ends of the allele to be inherited together for its function, or does the suppression of recombination at the locus ensure that the entire genetic region is inherited as a single unit? Ultimately, this thesis tests the hypothesis that: The co-inheritance of multiple genes within the 654kb LOP region is necessary to elicit LOP function in the model apomictic in P. piloselloides var. praealta R35. The null hypothesis is that only PAR is required for LOP function.Item Restricted The importance of species addition ‘versus’ replacement varies over succession in plant communities after glacier retreat(Springer Nature, 2024-02)The mechanisms underlying plant succession remain highly debated. Due to the local scope of most studies, we lack a global quantification of the relative importance of species addition ‘versus’ replacement. We assessed the role of these processes in the variation (β-diversity) of plant communities colonizing the forelands of 46 retreating glaciers worldwide, using both environmental DNA and traditional surveys. Our findings indicate that addition and replacement concur in determining community changes in deglaciated sites, but their relative importance varied over time. Taxa addition dominated immediately after glacier retreat, as expected in harsh environments, while replacement became more important for late-successional communities. These changes were aligned with total β-diversity changes, which were more pronounced between early-successional communities than between late-successional communities (>50 yr since glacier retreat). Despite the complexity of community assembly during plant succession, the observed global pattern suggests a generalized shift from the dominance of facilitation and/or stochastic processes in early-successional communities to a predominance of competition later on.
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