1,720,969 research outputs found
Ecological Drivers and Temporal Dynamics of \u3ci\u3eDaphnia\u3c/i\u3e in a Diverse Environmental and Spatial Landscape
No full textIn the modern era, commonly referred to as the Anthropocene, human-caused changes to the environment are prevalent and complex. The study of impacts to biodiversity and ecosystem functioning requires multi-faceted approaches that encompass scales of organization from genes to ecosystems. It is often difficult to tease apart whether species responses to environmental change are due to phenotypic plasticity or genotypic variation. Therefore, it is important to try to understand where variation originated, that is, to link a phenotypic response to a genetic change or to gauge whether the response is from the environment. In addition, neutral genetic variation arising from gene flow or genetic drift structures populations and can be influenced by environmental change. Understanding how phenotypic and genotypic variation originate and are maintained is necessary to better grasp the drivers of and responses to environmental change. In my dissertation, I focused on Daphnia, a cladoceran zooplankter with a diverse life history, genome, and mechanisms of dispersal. My goals were to collect genetic and phenotypic measurements from Daphnia across a diverse and geographically widespread group of lakes and multiple time periods to learn how ecological drivers might structure variation in the face of environmental change.
Lakes possess an island-like nature with well-defined boundaries and are therefore amenable to the study of local individual and population variation, as well as ecological interactions. Additionally, lakes are connected across landscapes to other water bodies, the terrestrial landscape, and the atmosphere. Lakes are also repositories of information over time through accumulation and preservation of physical, chemical, and biological materials in the sediment. In addition, lakes are often home to organisms that have been transported across the intervening landscape, such as plants and zooplankton, through vectors such as wind, water, animals, or even humans.
My study lakes were in the arid Channeled Scablands region of southeast Washington, east of the Cascade Mountain range, including some of the lakes and canal systems of the Columbia Basin Project (CBP). Other study lakes outside of the CBP, while not subject to water construction projects, were also subjected to multiple stressors.
I provide background information about the relevance of lakes and zooplankton, particularly Daphnia to the overall scope of the study in Chapter 1. In Chapter 2, I used population genetic analysis combined with environmental data collected from the study lakes and information on dispersal vectors in this region to model drivers of genetic variation over a broad geographic range. I found both evidence of Daphnia gene flow between two lakes across a highly trafficked interstate corridor and relationships in some lakes between genetic variation and bird dispersal, indicating that this species was dispersed by human and bird vectors. Next, in Chapter 3, I researched changes to Daphnia abundance and size over time in a single lake that had been subjected to known historical anthropogenic changes and contemporary recovery. Daphnia produce resting eggs that are preserved in the sediment and can persist for decades to centuries. In Chapter 3, I compared lake sediment nutrient data to that from preserved resting eggs over approximately 150 years from sediment cores. I found a positive relationship between sediment nutrients and resting egg abundance, allowing a reconstruction of possible environmental variables that highlight trends of a long-term lake restoration effort. Finally, in Chapter 4, I explored Daphnia resting egg size as a proxy for adult female body size from multiple lakes between historical and contemporary time periods. I also evaluated hatching success of resting eggs between time periods. I evaluated relationships between abiotic and biotic variables, as well as hatching success, with resting egg size. I found evidence of shifts in trait richness, which is the range of trait values (here, size), within populations between the contemporary and historical time periods. I also found differences in hatching success between time periods, with higher hatching success in the historical time period.
In this dissertation, I found several trends that inform research into the ecology of lakes, especially how ecological drivers impact variation in the face of environmental change. First, I found patterns in population genetic variation showing that Daphnia is dispersed through diverse modes and had gene flow between lakes, indicating at least some ability to overcome the properties of cyclic parthenogenetic Daphnia populations that can lead to genetic structure from founder effects and local adaptation. My study showed that human-caused dispersal could have a disproportionate impact on Daphnia genetic variation across space. Additionally, I found a positive relationship between Daphnia abundance and nutrients over time, illustrating the sensitivity of populations to changes in environmental conditions. The study of Medical Lake was unique because the Daphnia population response tracked a restoration effort through time but also uncovered eutrophication patterns through the use of paleolimnological methods. Finally, I observed trends in body size over an environmental gradient and time, illustrating that Daphnia individuals respond to environmental changes and that these responses can be monitored over an informative temporal scale by studying sediment cores. I investigated intraspecific trait variation, specifically trait richness of body size, across a large geographic range and across time to understand Daphnia phenotypic variation. I also uncovered novel information on hatching processes of Daphnia, which could have critical impacts on ecological interactions and biodiversity in lakes.
Overall, I pursued several avenues of research that would be useful for management of species and ecosystems in the face of environmental change. Using genetic data to investigate patterns in organisms with diverse dispersal modes can inform how dispersal vectors are structuring populations across space. Research on threatened and endangered species, as well as non-native species could benefit from a closer look at genetic variation in order to see patterns of gene flow or genetic drift. Few lakes have long-term monitoring data, so therefore tracking environmental changes over time is difficult, and is especially useful for understanding baseline conditions for restoration. I found value in reconstructing disturbance and restoration with paleolimnological techniques. Finally, in my last chapter, I evaluated how individual variation in an important functional trait could inform drivers of environmental change. Several global lake management plans incorporate zooplankton as indicator species and this research indicates that those plans should continue and expand. By evaluating Daphnia at multiple scales of biological organization and across time and space, this dissertation uncovered ecological patterns and processes necessary to better understand the impacts anthropogenic change
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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