1,721,122 research outputs found
How decision problems arise and are solved by phytophagous insects
Get PDFBei der Eiablage müssen sich Pflanzen fressende Insekten wiederholt entscheiden, Eier auf Wirtspflanzen niedriger Qualität zu legen oder auf bessere Pflanzen zu warten. Diese Entscheidungen sind Fitness relevant, weil Larven sich je nach Wirt unterschiedlich entwickeln und weil Weibchen in diesem inter-temporären Optimierungsproblem sowohl zu wählerisch als auch nicht wählerisch genug sein und so nicht alle Eier bzw. Eier in zu geringer Qualität legen können. Meine Arbeit nutzt vier Ansätze um zu untersuchen, wie diese Entscheidungsprobleme entstehen und wie Weibchen diese strategisch lösen. Erstens benutze ich analytische Optimierungsmodelle um zu zeigen, dass ein evolutionärer Trade-Off zwischen Vermehrung und Überleben variierender evolutionär stabiler Ei- und Zeit-Limitierung führen kann, dass aber keiner dieser zwei Faktoren ignoriert werden darf. Zweitens stelle ich klar, dass in der Vergangenheit vorgeschlagene schematische Zeit- und Ei-Kosten der Eiablage sich nicht mit den wirklichen Selektionskräften auf die Ei-Anzahl decken und daher kein gutes Werkzeug zur Analyse von Eiablage-Strategien darstellen. Drittens zeige ich mit Optimierungs- und populationsgenetischen Modellen, dass räumliche Heterogenität in der Wirtsverfügbarkeit keine notwendige Bedingung für die Evolution von Generalismus ist, weil emergente Quellen-Senken Dynamiken die Anpassung der Insekten an marginale Habitate verhindern, wenn Migrationsraten nicht hoch sind. Viertens zeige ich an Agenten basierte Simulationen zum Beispiel des Aurorafalters, Anthocharis cardamines, dass der phänologische Spezialismus der Larven dieser Art den Eiablage-Generalismus der Weibchen zur Folge hat. Insgesamt zeigen diese vier Ergebnisse, wie nützlich theoretische Ansätze zur Untersuchung spezifischer Szenarios der strategischen Eiablage sein können und machen deutlich, dass die Evolution von Generalismus leichter aus zeitlicher denn aus räumlicher Heterogenität folgt.Ovipositing phytophagous insects repeatedly face the decision problem of laying eggs on lower-quality host plants or waiting out for higher-quality ones. These choices carry fitness costs and benefits because larvae develop differentially on different hosts and because, in this inter-temporal optimization task, females may be too choosy and die before laying all eggs (i.e. become time-limited) or not be choosy enough and run out of eggs before their death (i.e. become egg-limited). This thesis employs four approaches to examine how oviposition decision problems arise and how they are strategically solved by female insects. First, I use analytical optimization models to show that a life-history trade-off between survival and reproduction can lead to varying evolutionarily stable levels of egg and time limitation, but that neither egg nor time limitation can be ignored in evolutionary analyses of oviposition. Second, I highlight that such schematic time and egg costs of oviposition as advocated in the past do not match the actual forces of natural selection on egg number as partitioned between egg and time limitation and therefore represent a less useful practice to analyze oviposition strategies. Third, I use optimality and population genetic models to show that spatial heterogeneity in host availability is not a sufficient condition for the evolution of generalism because emergent source-sink dynamics preclude adaptation of insects to marginal habitats unless migration rates are high. Fourth, I employ individual-based simulations built around the case study of the orange tip butterfly, Anthocharis cardamines, to show that this species’ larvae’s phenological specialism may drive the adult females’ oviposition generalism. All these findings show the usefulness of theoretical approaches to examine specific questions of strategic oviposition. Moreover, they demonstrate that evolution of generalism more likely results from resource unpredictability in time than in space
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
Temperature effects on genetic and physiological regulation of adaptive plasticity
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This thesis contributed to a broader understanding of the genetic and physiological mechanisms that regulate developmental plasticity represented by butterfly wing color patterns.
We found that different groups of cells within the same tissue have sensitivities and patterns of response that are distinct for the external environmental cue and for the internal hormonal signal. We also showed that the spatial compartmentalization of these responses cannot be explained by the spatial or temporal compartmentalization of the hormone receptor protein, and that manipulating pupal ecdysteroid levels is sufficient to mimic in direction and magnitude the shifts in adult reproductive resource allocation.
We explored the effect of alleles of large effect on wing pattern on plasticity by characterizing thermal reaction norms for the size of eyespot rings for Bicyclus anynana mutants. Genotypes with alleles affecting eyespot size and color were the most sensitive to variation in developmental temperature. To explore genotype, temperature, and genotypextemperature effects on B. anynana development, we derived artificial selection lines expressing wet or dry-season-like phenotypes and, we characterized thermal reaction norms for a wider range of temperatures. Our results provided evidence for significant GxE effects, and also revealed a possible new color appearing at the most extreme low temperatures.
Animal science
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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