title: Spatial and temporal scales matter when assessing the species and genetic diversity of springtails (Collembola) in Antarctica

authors: Collins, Gemma Elyse

subjects: Science & Technology

abstract: Seven species of springtail (Collembola) are present in Victoria Land, Antarctica and all have now been sequenced at the DNA barcoding region of the mitochondrial cytochrome c oxidase subunit I gene (COI). Here, we review these sequence data (n = 930) from the GenBank and Barcode of Life Datasystems (BOLD) online databases and provide additional, previously unpublished sequences (n = 392) to assess the geographic distribution of COI variants across all species. Four species (Kaylathalia klovstadi, Cryptopygus cisantarcticus, Friesea grisea, and Cryptopygus terranovus) are restricted to northern Victoria Land and three (Antarcticinella monoculata, Cryptopygus nivicolus, and Gomphiocephalus hodgsoni) are found only in southern Victoria Land, the two biogeographic zones which are separated by the vicinity of the Drygalski Ice Tongue. We found highly divergent lineages within all seven species (range 1.7–14.7%) corresponding to different geographic locations. Levels of genetic divergence for the southern Victoria Land species G. hodgsoni, the most widespread species (~27,000 km2), ranged from 5.9 to 7.3% divergence at sites located within 30 km, but separated by glaciers. We also found that the spatial patterns of genetic divergence differed between species. For example, levels of divergence were much higher for C. terranovus (>10%) than for F. grisea (<0.2%) that had been collected from the same sites in northern Victoria Land. Glaciers have been suggested to be major barriers to dispersal and two species (C. cisantarcticus and F. grisea) showed highly divergent (>5%) populations and over 87% of the total genetic variation (based on AMOVA) on either side of a single, 16 km width glacier. Collectively, these data provide evidence for limited dispersal opportunities among populations of springtails due to geological and glaciological barriers (e.g., glaciers and ice tongues). Some locations harbored highly genetically divergent populations and these areas are highlighted from a conservation perspective such as avoidance of human-mediated transport between sites. We conclude that species-specific spatial and temporal scales need to be considered when addressing ecological and physiological questions as well as conservation strategies for Antarctic Collembola.

text: Spatial and temporal scales matter when assessing the species and genetic diversity of springtails (Collembola) in Antarctica Seven species of springtail (Collembola) are present in Victoria Land, Antarctica and all have now been sequenced at the DNA barcoding region of the mitochondrial cytochrome c oxidase subunit I gene (COI). Here, we review these sequence data (n = 930) from the GenBank and Barcode of Life Datasystems (BOLD) online databases and provide additional, previously unpublished sequences (n = 392) to assess the geographic distribution of COI variants across all species. Four species (Kaylathalia klovstadi, Cryptopygus cisantarcticus, Friesea grisea, and Cryptopygus terranovus) are restricted to northern Victoria Land and three (Antarcticinella monoculata, Cryptopygus nivicolus, and Gomphiocephalus hodgsoni) are found only in southern Victoria Land, the two biogeographic zones which are separated by the vicinity of the Drygalski Ice Tongue. We found highly divergent lineages within all seven species (range 1.7–14.7%) corresponding to different geographic locations. Levels of genetic divergence for the southern Victoria Land species G. hodgsoni, the most widespread species (~27,000 km2), ranged from 5.9 to 7.3% divergence at sites located within 30 km, but separated by glaciers. We also found that the spatial patterns of genetic divergence differed between species. For example, levels of divergence were much higher for C. terranovus (>10%) than for F. grisea (<0.2%) that had been collected from the same sites in northern Victoria Land. Glaciers have been suggested to be major barriers to dispersal and two species (C. cisantarcticus and F. grisea) showed highly divergent (>5%) populations and over 87% of the total genetic variation (based on AMOVA) on either side of a single, 16 km width glacier. Collectively, these data provide evidence for limited dispersal opportunities among populations of springtails due to geological and glaciological barriers (e.g., glaciers and ice tongues). Some locations harbored highly genetically divergent populations and these areas are highlighted from a conservation perspective such as avoidance of human-mediated transport between sites. We conclude that species-specific spatial and temporal scales need to be considered when addressing ecological and physiological questions as well as conservation strategies for Antarctic Collembola.

year: 2019

title: Efficient remittance services for development in the Pacific

authors: Gibson, John

subjects: Pacific

abstract: Capital inflows to the Pacific islands from aid, foreign investment and remittances are an important source of development finance. Remittances are the fastest growing; they now total US$ 400 million per year and can be expected to grow even further as labour mobility is used to deal with seasonal labour shortages in Australia and New Zealand and limited job opportunities in the Pacific. The transaction costs of sending remittances to the Pacific islands are very high for the most widely used methods. This paper examines the New Zealand- Tonga remittance corridor, where typical transactions involve costs in the order of 15 to 20 per cent for bank drafts and transfers through money transfer companies such as Western Union. Cheaper transfer methods using automated teller machines (ATMs) are feasible and have transaction costs of less than 5 per cent but are not widely used. This spread of 10 percentage points between the most popular and the cheapest remittance methods means a potential loss for Tonga of the equivalent of 4 per cent of GDP. Extrapolating from this remittance corridor to the rest of the Pacific, avoidable transaction costs may total US$ 40 million per year. Hypotheses about the continued reliance on high transaction cost methods are examined and implications for development policy are discussed.

text: Efficient remittance services for development in the Pacific Capital inflows to the Pacific islands from aid, foreign investment and remittances are an important source of development finance. Remittances are the fastest growing; they now total US$ 400 million per year and can be expected to grow even further as labour mobility is used to deal with seasonal labour shortages in Australia and New Zealand and limited job opportunities in the Pacific. The transaction costs of sending remittances to the Pacific islands are very high for the most widely used methods. This paper examines the New Zealand- Tonga remittance corridor, where typical transactions involve costs in the order of 15 to 20 per cent for bank drafts and transfers through money transfer companies such as Western Union. Cheaper transfer methods using automated teller machines (ATMs) are feasible and have transaction costs of less than 5 per cent but are not widely used. This spread of 10 percentage points between the most popular and the cheapest remittance methods means a potential loss for Tonga of the equivalent of 4 per cent of GDP. Extrapolating from this remittance corridor to the rest of the Pacific, avoidable transaction costs may total US$ 40 million per year. Hypotheses about the continued reliance on high transaction cost methods are examined and implications for development policy are discussed.

year: 2007

title: Visualising categorical data: Linguistic case studies from te Reo Māori and New Zealand English

authors: Trye, David

subjects: visualisation

abstract: Categorical variables are prevalent in real-world datasets across numerous domains, yet few visualisation techniques accommodate them effectively. This is especially true of datasets comprising three or more categorical variables, termed multivariate categorical data. Visualising such data is challenging due to the lack of inherent ordering of nominal categories, the so-called ‘curse of dimensionality’, and the potential variability in the number of categories per variable. Corpus linguistics, which involves the study of large digital collections of naturally occurring language, serves as the primary application domain in this thesis. This domain was chosen because it is rich in multivariate categorical data and, at the same time, is often visualised using only basic techniques.

This thesis contributes to the area of categorical data visualisation in several ways. First, we propose a taxonomy of techniques for visualising categorical data, highlight limitations of existing solutions, and identify relevant analysis tasks. Building on this foundation, the thesis introduces novel techniques and enhancements for visualising datasets involving multiple categorical variables. We focus on adapting the layout and interactive capabilities of an existing technique that uses a matrix of heatmaps to represent pairwise category intersections. These modifications show that directly visualising statistical test results for categorical data can be beneficial for exploring bivariate patterns and associations. Furthermore, we contribute the design, implementation and evaluation of a novel technique called MultiCat, which is not restricted to pairwise intersections but rather facilitates analysis of relationships among multiple variables simultaneously. Both these techniques are interactive and offer greater scalability than existing alternatives, thereby affording new possibilities for analysing multivariate categorical data. However, since categorical variables can occur within more complex data structures, we also consider their presence in networks and hypergraphs, which require specialised methods.

To demonstrate the application of these techniques, we draw on two linguistic case studies that focus on languages of special significance in Aotearoa New Zealand. Addressing the low-resource status of Māori, the country’s Indigenous language, we first contribute two related Twitter datasets—a monolingual Māori corpus and a mixed–language Māori–English corpus—together with an architecture for differentiating Māori and English words. Our initial case study uses the monolingual Māori corpus and proposed visualisation techniques to investigate grammatical possession in Māori, offering fresh insights into the linguistic practices of contemporary speakers. The second case study uses networks and hypergraphs with categorical attributes to explore Māori loanword co-occurrence in New Zealand English newspaper articles. We find that loanwords tend not to occur in isolation and that New Zealanders are still importing new (unlisted) borrowings from Māori.

Ultimately, the techniques developed in this thesis have broad applications both within and beyond the corpus linguistics community. By enabling more effective visualisation and analysis of multivariate categorical data, this research has the potential to facilitate deeper insights into domains as diverse as education, healthcare, business and science.

text: Visualising categorical data: Linguistic case studies from te Reo Māori and New Zealand English Categorical variables are prevalent in real-world datasets across numerous domains, yet few visualisation techniques accommodate them effectively. This is especially true of datasets comprising three or more categorical variables, termed multivariate categorical data. Visualising such data is challenging due to the lack of inherent ordering of nominal categories, the so-called ‘curse of dimensionality’, and the potential variability in the number of categories per variable. Corpus linguistics, which involves the study of large digital collections of naturally occurring language, serves as the primary application domain in this thesis. This domain was chosen because it is rich in multivariate categorical data and, at the same time, is often visualised using only basic techniques.

This thesis contributes to the area of categorical data visualisation in several ways. First, we propose a taxonomy of techniques for visualising categorical data, highlight limitations of existing solutions, and identify relevant analysis tasks. Building on this foundation, the thesis introduces novel techniques and enhancements for visualising datasets involving multiple categorical variables. We focus on adapting the layout and interactive capabilities of an existing technique that uses a matrix of heatmaps to represent pairwise category intersections. These modifications show that directly visualising statistical test results for categorical data can be beneficial for exploring bivariate patterns and associations. Furthermore, we contribute the design, implementation and evaluation of a novel technique called MultiCat, which is not restricted to pairwise intersections but rather facilitates analysis of relationships among multiple variables simultaneously. Both these techniques are interactive and offer greater scalability than existing alternatives, thereby affording new possibilities for analysing multivariate categorical data. However, since categorical variables can occur within more complex data structures, we also consider their presence in networks and hypergraphs, which require specialised methods.

To demonstrate the application of these techniques, we draw on two linguistic case studies that focus on languages of special significance in Aotearoa New Zealand. Addressing the low-resource status of Māori, the country’s Indigenous language, we first contribute two related Twitter datasets—a monolingual Māori corpus and a mixed–language Māori–English corpus—together with an architecture for differentiating Māori and English words. Our initial case study uses the monolingual Māori corpus and proposed visualisation techniques to investigate grammatical possession in Māori, offering fresh insights into the linguistic practices of contemporary speakers. The second case study uses networks and hypergraphs with categorical attributes to explore Māori loanword co-occurrence in New Zealand English newspaper articles. We find that loanwords tend not to occur in isolation and that New Zealanders are still importing new (unlisted) borrowings from Māori.

Ultimately, the techniques developed in this thesis have broad applications both within and beyond the corpus linguistics community. By enabling more effective visualisation and analysis of multivariate categorical data, this research has the potential to facilitate deeper insights into domains as diverse as education, healthcare, business and science.

year: 2024