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Species interactions and diversity: A unified framework using Hill numbers
No full textBiodiversity describes the variety of organisms on planet earth. Ecologists have long hoped for a synthesis between analyses of biodiversity and analyses of biotic interactions among species, such as predation, competition, and mutualism. However, it is often unclear how to connect details of these interactions with complex modern analyses of biodiversity. Using methods pioneered in studies of ecological-evolutionary dynamics, we link biotic interactions and changes in measures of biodiversity such as Hill numbers. We show that analyses of biodiversity obscure details about biotic interactions. For example, identical changes in biodiversity can arise from predation, competition or mutualism, locally or across a metacommunity. Our approach indicates that traditional models of community assembly miss key facets of diversity change. Instead, we suggest that analyses of diversity change should focus on partitions, which measure mechanisms that directly shape changes in diversity, notably relative fitness and immigration, rather than traditional analyses of biotic interactions
Quantile-on-quantile connectedness measures: Evidence from the US treasury yield curve
No full textThis study introduces a novel quantile-on-quantile connectedness approach to explore reversely related and directly related quantile spillovers. To illustrate the benefits of the proposed method, we examine the spillovers across the 2-year US Treasury yield (US2Y) and the yield curve spread between the 10-year and 2-year US Treasury yield (US2Y10Y) from 13 July 1998 to 11 July 2023. The empirical results show that the average total connectedness between reversely related quantiles is substantially higher than directly related quantiles. Additionally, the average quantile-based total connectedness is heterogeneous over time and economic events dependent
First report of accumulation of Lyngbyatoxin-A in edible shellfish in Aotearoa New Zealand from marine benthic cyanobacteria
No full textThis study reports the first documented accumulation of lyngbyatoxin-a (LTA), a cyanotoxin produced by marine benthic cyanobacteria, in edible shellfish in Aotearoa New Zealand. The study investigates two bloom events in 2022 and 2023 on Waiheke Island, where hundreds of tonnes of marine benthic cyanobacterial mats (mBCMs) washed ashore each summer. Genetic analysis identified the cyanobacterium responsible for the blooms as Okeania sp., a genus typically found in tropical marine ecosystems. Analysis by liquid chromatography–tandem mass spectrometry indicated that the cyanobacteria produced a potent dermatoxin, lyngbyatoxin-a (LTA), and that LTA had accumulated in marine snails, rock oysters and cockles collected near the mats. Snails contained the highest levels of LTA (up to 10,500 µg kg¯¹). The study also demonstrated that the LTA concentration was stable in composted mats for several months. The presence of LTA in edible species and its stability over time raise concerns about the potential health risks to humans consuming LTA-contaminated seafood. This underlines the need for further studies assessing the risks of human exposure to LTA through seafood consumption, particularly as climate change and eutrophication are expected to increase the frequency of mBCM blooms. The study highlights the need to develop public health risk management strategies for mBCMs
Sedimentary ancient DNA reveals the impact of anthropogenic land use disturbance and ecological shifts on fish community structure in small lowland lake
No full textFreshwater fish biodiversity and abundance are decreasing globally. The drivers of decline are primarily anthropogenic; however, the causative links between disturbances and fish community change are complex and challenging to investigate. We used a suite of sedimentary DNA methods (droplet digital PCR and metabarcoding) and traditional paleolimnological approaches, including pollen and trace metal analysis, ITRAX X-ray fluorescence and hyperspectral core scanning to explore changes in fish abundance and drivers over 1390 years in a small lake. This period captured a disturbance trajectory from pre-human settlement through subsistence living to intensive agriculture. Generalized additive mixed models explored the relationships between catchment inputs, internal drivers, and fish community structure. Fish community composition distinctly shifted around 1350 CE, with the decline of a sensitive Galaxias species concomitant with early land use changes. Total fish abundance significantly declined around 1950 CE related to increases in ruminant bacterial DNA (a proxy for ruminant abundance) and cadmium flux (a proxy for phosphate fertilizers), implicating land use intensification as a key driver. Concurrent shifts in phytoplankton and zooplankton suggested that fish communities were likely impacted by food web dynamics. This study highlights the potential of sedDNA to elucidate the long-term disturbance impacts on biological communities in lakes
Parental financial support for housing: The importance of investment homes and family size
No full textAs global housing affordability declines among young people, parental financial housing support has become a crucial mechanism for the transmission of family housing wealth. This study aims to assess the influence of parental ownership of primary and investment properties on the mechanism of providing housing support to their offspring. Using data from a representative survey of the New Zealand population, our study reveals that parental ownership of investment properties plays a predominant role in their ability to provide housing support to their children, whereas the ownership of primary residences does not affect this support. Interestingly, we find that that this effect remains significant even after controlling for parental household income and savings. This suggests that the impact of investment properties on housing support is not solely attributed to their contribution to income or savings. Furthermore, our findings indicate that parental ownership of investment properties has a more pronounced impact on providing substantial housing support. Additionally, wealth inequality in housing transmission appears to be more prominent in households with multi-child. As the effect of parental housing are significant in multi-child families, an effect not observed in one-child households. These findings reveal the inequality in the transmission of housing wealth through the mechanism of parental housing support
Attitudes and behaviour intention in consuming plant-based food: Evidence from young tourists in Indonesia
No full textPurpose – This research aims to observe the attitudes and behavioural intentions of young tourists in relation to their experiences of consuming PBF, including value consumption, concern for the environment and perceived cost as influencing factors.
Methodology/Design/Approach – Considering that it is almost impossible to determine the sample frame for young tourists in Indonesia, this research used a non-probability sample to collect the sample. The study focused on young tourists aged 18 to 35 years old who have experience of consuming PBF while travelling. A self-administered online questionnaire was provided to tourists visiting a destination from July to September 2022, resulting in 267 usable responses.
Findings – Tourists’ attitude towards PBF leads to their intention to buy again during or after their visit and to offer profitable e-WOM. In addition, perceived cost moderates the relationship between attitude and e-WOM; however, it does not provide evidence for the moderating role between attitude and repurchase intention.
Originality of the research – This study highlights the value of consumption, concern for the environment and perceived costs as factors influencing tourists’ attitudes and behavioural intentions towards public transport
Assessing the prevalence, diversity, and damage potential of plant-parasitic nematodes on maize (Zea mays L.) : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
No full textMaize cultivation faces challenges from plant-parasitic nematodes (PPNs), which can significantly reduce yields. Despite their importance, PPNs are often underestimated in agricultural ecosystems. Research in New Zealand and Sri Lanka reported the presence of PPNs in maize fields. However, comprehensive data is still lacking. Environmental factors such as soil pH, moisture content, nutrient levels, and rainfall could influence PPN population densities and pathogenicity. Hence, understanding PPN dynamics and environmental interactions is crucial for sustainable production. This study aimed to; i) examine the prevalence, abundance, and distribution of PPNs associated with maize cultivation in Sri Lanka and New Zealand, ii) identify the most abundant PPN species and their distribution in New Zealand maize fields, iii) investigate the relationship between soil edaphic and climatic characteristics with PPN abundance in New Zealand maize fields, and iv) screen the susceptibility of commercially available maize hybrids in New Zealand against the most abundant PPN genus under glasshouse conditions. A survey conducted in Sri Lanka's semi-arid regions with major maize cultivation areas found that over 92% of maize fields tested positive for PPNs. The dominant species was Pratylenchus spp., with a mean population density of 2020 kg-1 of soil. Sampling at different maize growth stages revealed that Pratylenchus spp. populations were below 1000 kg-1 of soil at the seedling stage but increased by 2 to 10-fold at harvest. In New Zealand, a total of 384 soil samples were collected from 25 sites from both the North (NI) and South Island (SI) of New Zealand from maize growing regions. The major PPNs identified by morphology were Pratylenchus (91%), Helicotylenchus (38%), Meloidogyne (14%), Tylenchus (14%), Heterodera (8%), Paratylenchus (3%), and Criconemella (1%). Pratylenchus spp. were widespread across all surveyed regions. In most sampled sites from both islands, Pratylenchus spp. exceeded 1000 kg-1 of soil, which is recognised as the economic threshold set by nematologists worldwide. Five Pratylenchus spp. in New Zealand maize fields: P. crenatus, P. neglectus, P. thornei, P. penetrans, and P. pratensis, were identified based on morphology and the sequencing of DNA-PCR products extracted from single nematode using Sanger sequencing. Among these, P. crenatus and P. neglectus were predominant across maize-growing regions in New Zealand. The soil analysis revealed that tested soil properties varied between the sampled regions, while PPN abundance and diversity exhibited a regional dissimilarity. The relationship between PPN composition and soil physicochemical properties of New Zealand maize fields analysed using the canonical correspondence analysis (CCA). Results showed that soil moisture, pH, soil P, and percentages of sand, clay, N, and C significantly influenced PPN abundance and distribution. However, the influence of soil parameters on the PPN population varied within the regions, where soil moisture content was the main driver for the PPN population abundance within all three regions. A year-round sampling conducted at one of the sites in the Canterbury region of SI revealed the influence of seasonal and cropping factors on PPN abundance. This indicated a 5-fold population increase of Pratylenchus spp. from crop establishment to maturity during a season. Also, CCA on seasonal variations on soil physicochemical, climatic factors, and PPN population abundance in a field revealed that the soil moisture, volumetric water content, bulk density, sand%, N and C with the climatic factors; rainfall, relative humidity, and sunshine hours had a significant relationship with PPN population dynamics. Three nematode extraction methods for maize roots were tested. Centrifugal sugar flotation yielded the highest nematode count but with low clarity for microscopic observation. The Baermann funnel had 35.9% extraction efficiency with high clarity. The Whitehead tray had 60.8% efficiency with moderate clarity compared to centrifugal sugar flotation. The Whitehead tray is a good compromise for clarity and count, while sugar flotation is efficient and faster processing of samples for Pratylenchus nematodes, adding another layer of information for future studies. The outcomes from the glasshouse experiments using 15 commercial maize hybrids and a mixed field population of Pratylenchus spp. showed that most tested maize hybrids were susceptible to Pratylenchus spp. and demonstrated varying degrees of susceptibility. Another glasshouse experiment was conducted to determine the pathogenicity and reproduction of Pratylenchus on three selected maize hybrids based on the results from the previous trials. The results demonstrated significant reductions in root dry weight across hybrids, with losses ranging from 33% to 42%, and shoot weight losses varied among hybrids 10 to 22% compared to the controls 60 days after planting. This is the first comprehensive study on the PPN community association with maize in Sri Lanka and New Zealand. These findings emphasised the potential impact of PPNs, particularly Pratylenchus spp., on maize yield in both countries, highlighting the urgent need for further research to develop effective PPN management tactics adapted to local conditions
Adaptive flood mitigation planning: Harnessing the maximum capability of strategic green stormwater infrastructure
No full textFlooding in low-lying coastal cities is expected to worsen with climate change, and planning for long-term flood mitigation is challenging due to high uncertainty in projections. Risks are associated with under- or over-investment in expensive grey infrastructure. Implementing green stormwater infrastructure (GSI) on strategically large private properties may be a lower-risk alternative. In our previous studies published in 2022 and 2024, we found that the capability of industrial properties to supplement city flood mitigation was substantial. They could offset climate change impacts in the long term, even under a major climate change scenario, and reduce flood probabilities. In this paper, we restate their potential as a case study of large private properties to draw more attention from practitioners and transfer scientific knowledge into practice. The maximum flood mitigation capabilities of large private properties can be met through networks of GSI facilities and a long-term adaptation plan that considers all possible approaches to implementing GSI over time. However, government regulations and policies are needed to support their implementation to the maximum capabilities
Elevated carbon-dioxide effects on wheat grain quality differed under contrasting nitrogen and phosphorus fertiliser supply
No full textAtmospheric carbon-dioxide concentration ([CO₂]) is increasing rapidly, but its interactions with nitrogen (N) and phosphorus (P) fertiliser on wheat grain quality are not well understood. We investigated the effects of ambient CO2 (aCO₂; ∼410 ppm) and elevated CO₂ (eCO₂; 760 ppm) on crop harvest index (CHI), nutrient harvest index (NuHI), shoot macro-nutrient content and grain macro-nutrient concentration of wheat grown under two contrasting amounts of N (0.5 and 6 mol m¯³ NO₃‾ N) and P (10 and 250 mmol P m¯³) fertiliser supply (low and optimum, respectively). Our results highlighted interactions between [CO₂] and N and P fertiliser supply for the shoot biomass at anthesis and straw biomass at harvest maturity. This was because biomass yield did not respond to CO₂ level when fertiliser was deficient. However, shoot and straw yield increased (10.0–-34.0%) with increasing [CO₂] at optimum fertiliser rates. Across experiments, grain yield increased (15.6%) with increasing [CO₂], which resulted in grain nutrient concentration decreasing (3.0–-13.0%) with increasing [CO₂]. This was attributed to nutrient 'dilution' due to increased carbohydrate content in the grain. Overall, fertiliser supply impacted crop responses more than CO₂ treatments, and the impact was greater under N than P deficiency. This was reflected through conservative values for CHI, thousand grain weight and NuHIs suggesting plants allocated biomass and nutrients at similar rates for vegetative and reproductive organs independent of [CO₂]
Turning up the heat: Climate change consequences for Pinot Noir berry quality
No full textTemperature increase due to climate change affects grapevine productivity and berry quality. Studies have shown that higher temperatures lead to increased sugar concentrations at harvest, or earlier harvests to retain the same sugar targets. Temperature increases may also impact anthocyanins (colour) and amino acids crucial for fermentation. New Zealand researchers set out to explore how microclimates influence anthocyanin, phenolic compounds and amino acids in Pinot Noir