1,721,004 research outputs found
Herbivory-mediated pollinator limitation: negative impacts of induced volatiles on plant-pollinator interactions
No full textAlthough induced plant responses to herbivory are well studied as mechanisms of resistance, how induction shapes community interactions and ultimately plant fitness is still relatively unknown. Using a wild tomato, Solanum peruvianum, native to the Peruvian Andes, we evaluated the disruption of pollination as a potential ecological cost of induced responses. More specifically, we tested the hypothesis that metabolic changes in herbivore-attacked plants, such as the herbivore-induced emission of volatile organic compounds (VOCs), alter pollinator behavior and consequentially affect plant fitness. We conducted a series of manipulative field experiments to evaluate the role of herbivore-induced vegetative and floral VOC emissions as mechanisms by which herbivory affects pollinator behavior. In field surveys and bioassays in the plants' native habitat, we found that real and simulated herbivory (methyl jasmonate application) reduced attractiveness of S. peruvianum flowers to their native pollinators. We show that reduced pollinator preference, not resource limitation due to leaf tissue removal, resulted in reduced seed set. Solitary bee pollinators use floral plant volatiles, emitted in response to herbivory or methyl jasmonate treatment, as cues to avoid inflorescences on damaged plants. This herbivory-induced pollinator limitation can be viewed as a general cost of induced plant responses as well as a specific cost of herbivory-induced volatile emission
Mechanisms of jasmonate-induced activation of defense responses in Nicotiana attenuata
Full text linkDie Zielsetzung dieser Arbeit war die Identifizierung und Charakterisierung der chemischen Signalstoffe im Regurgitat der Raupen des Tabakschwärmers Manduca sexta und der endogenen Signalkaskaden der wilden Tabakpflanze Nicotiana attenuata, die die herbivoren-spezifische Abwehrreaktionen in N. attenuata induzieren. Manuskript I und II beschreiben die Isolierung und Charakterisierung von Fettsäure-Aminosäure-Konjugaten als Elicitoren in den oralen Sekreten von M. sexta Raupen. Diese aktiven Substanzen sind für die Erkennung des Frassbefalls in der wilden Tabakpflanze N. attenuata verantwortlich, amplifizieren die endogene, durch Verwundung induzierte, Jasmonsäurebiosynthese und Herbivoren-spezifische direkte und indirekte Abwehrmechanismen. Durch antisense Transformation wurde die Expression von Genen der durch Raupenfrass oder Behandlung mit Elicitoren in der Pflanze aktivierten Biosynthese von Jasmonsäure und verwandten Signalstoffen manipuliert (Manuscript III) und die Auswirkungen der verminderten Induzierbarkeit auf die Resistenz von N. attenuata in Labor- (Manuskript IV und V) und Freilandversuchen (Manuskript VI) untersucht. Die Laborversuche zeigten eine verminderte Induktion von indirekten (Duftstoffemission) und direkten (Proteinase Inhibitor Aktivität, Nikotin Produktion) Abwehrreaktionen und eine damit verbundende reduzierte Resistenz gegen Raupenfrass durch M. sexta in den transformierten Pflanzen mit verringerter Jasmonsäurebiosynthese. In Freilandversuchen im natürlichen Habitat von N. attenuata wurden die transformierten Pflanzen, zusätzlich zur verminderten Resistenz gegen M. sexta Frass, von zwei oportunistischen Herbivoren (Diabrotica undecimpunctata und Empoasca spec.), die nicht auf Wildtyp N. attenuata Pflanzen beobachtet wurden, attackiert
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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