1,720,987 research outputs found
Levels and Patterns of Genetic Diversity in Wild Populations and Cultured Stocks of Cherax Quadricarinatus (von Martens, 1868) (Decapoda: Parastacidae)
No full textStudying species at the molecular level can provide insights into how ecological and biological processes interrelate resulting in the diversity we see today. This information can be applied to conserve species at risk of extinction, or to better manage genetic diversity in species of economic importance. Species that inhabit freshwater riverine systems commonly exhibit population structures that are related to their relative dispersal capability, contemporary stream structure and/or historical stream structure. This thesis examined the populations genetic structure of wild and cultured stocks of the commercially farmed freshwater crayfish, C. quadricarinatus (von Martens), using genetic markers characterized by different modes of inheritance. C. quadricarinatus is distributed naturally in riverine systems in northern Australia, and southern Paupa New Guinea (PNG) and inhabits a variety of freshwater ecosystems ranging from ephemeral to permanent. Life history characteristics of C. quadricarinatus suggest a high level of genetic structuring among wild stocks might exist. However, seasonal flooding coupled with low topography across its distribution in northern Australia may promote sufficient gene flow among rivers to produce genetic homogeneity. Historical gene flow may also influence modern genetic structure as many distinct riverine catchments that C. quadricarinatus inhabits, were once connected at times of lower sea level. Insight into genetic relationships among C. quadricarinatus populations will allow for better management practices of wild populations in the future.
The study investigated phylogenetic relationships among C. quadricarinatus representing 17 discrete natural drainages across the natural range in Australia and PNG, using 16s and COI gene sequences. Sequence analysis of both genes resolved two distinct genealogical lineages in Australia and three in PNG. The two divergent Australian lineages concur with original taxonomic descriptions of Reik (1969) based on external morphological differences. The three C. quadricarinatus populations sampled in PNG were all genetically distinct from each other, with one exhibiting a close association with an Australia lineage. The immense physical barriers (rugged mountain ranges) to gene flow in PNG will almost certainly have reduced dispersal capabilities for C. quadricarinatus. During times of lowered sea levels in the past, Australia and southern PNG were a single landmass with terrestrial and freshwater organisms theoretically able to disperse over associated land and via freshwater connections. The close genetic relationship between PNG and Australian C. quadricarinatus support a recent freshwater connection and hence gene flow between northern Australia and PNG C. quadricarinatus populations.
Genetic differentiation among some C. quadricarinatus lineages exhibit as much genetic divergence at 16s RNA sequences as taxonomically recognised sub-species in the Cherax genus. Since C. quadricarinatus was originally described as different species based on external morphological differences (Reik, 1969), it is recommended that the taxonomy of C. quadricarinatus in Australia and PNG be re-evaluated.
C. quadricarinatus specific microsatellite markers were developed for this study. Five variable loci were employed to investigate the extent of contemporary gene flow among fourteen C. quadricarinatus wild river populations in northern Australia. High FST and genetic distance estimates observed among pair wise comparisons of C. quadricarinatus populations are consistent with limited or no gene flow occurring among drainages. Speculation that C. quadricarinatus may disperse between adjacent or nearby drainages at times of flood, either across floodplains, or via flood plumes therefore seems highly unlikely among the populations examined in the current study. No significant correlation was observed between geographic distance and genetic distance among C. quadricarinatus populations here. C. quadricarinatus populations most closely resemble an island-like model, where gene flow is independent of geographic distance among populations and where genetic divergence occurs to a greater or lesser extent as a result of genetic drift within otherwise isolated populations.
A significant number of C. quadricarinatus populations showed deviations from expected Hardy-Weinberg equilibrium (HWE). Samples sizes may not have been sufficiently large to reflect a true representation of genotypic proportions present in the sampled populations due to the highly variable nature of microsatellite loci. Deviations from HWE equilibrium, however, can also result from null alleles. Null allele estimates suggested a large proportion of null alleles were present in the C. quadricarinatus populations analysed. This may be a result of C. quadricarinatus populations confined to discrete drainages experiencing independent evolution, resulting in mutations in primer binding sites.
The growing economic potential of C. quadricarinatus culture, both domestically and internationally, prompted expanding the current study to examine genetic diversity levels in commercial C. quadricarinatus stocks. The study employed five microsatellite markers to quantify genetic diversity in four Australian and three C. quadricarinatus culture stocks from overseas. Many C. quadricarinatus culture stocks also showed deviations from HWE expectations. This was not a surprising result given that the wild populations also deviated and domestication can also influence HWE. Relatively high levels of genetic diversity were observed. This probably results from intentional mixing of discrete river strains for production of the first commercial stock. Genetic differentiation estimates among culture stocks and assignment tests indicated that overseas culture stocks are most likely derived from the first commercial culture stock developed in Australia and then disseminated widely (the Hutchings stock). Robin Hutchings was a known supplier of live C. quadricarinatus to many international culture initiatives. Assignment of culture stocks back to their wild origins indicated that all C. quadricarinatus culture stocks sampled possess alleles that originate from the Flinders River (proportions ranged from 33-94%).
Domestication of C. quadricarinatus to date has not resulted in significant reductions in levels of genetic diversity (heterozygosity or alleles richness) when compared to wild populations sampled in this study. Comparing culture stocks to wild populations to gauge their 'genetic health' may not be a suitable scale for evaluating genetic diversity in culture stocks. Wild populations are essentially evolving independently, are subjected to harsh seasonal environmental fluctuations resulting in periodic population crashes (genetic bottlenecks), with little or no recruitment from neighbouring drainages (gene flow). This study does however indicate that there is a large amount of genetic diversity distributed among wild populations that has yet to be exploited in culture. Genetic diversity in wild populations provides a resource for future stock improvement programs for C. quadricarinatus culture and thus requires careful conservation and appropriate management
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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