1,720,958 research outputs found
Adaptive diversification in experimental populations of Escherichia coli
No full textWhat processes contribute to the origin and maintenance of biological diversity? When populations occupy different environments, that have divergent ecological characteristics, natural selection can cause each population to adapt to its environment, resulting in phenotypic divergence between populations. But can natural selection cause a single population to diverge? Adaptive dynamics theory predicts that ecological interactions between individuals in a population can result in negative frequency-dependent selection, and the branching of the population into phenotypically distinct subpopulations. Here, I tested predictions from adaptive dynamics theory. To do this, I experimentally evolved populations of the clonal bacterium Escherichia coli in the lab. First, using replicate populations of E. coli that had diversified in parallel, I tested whether convergent ecotypes among replicate populations competed in a likewise manner. I found they do not, suggesting that the genetic underpinnings of the convergent ecotypes among populations were different. The ecological interaction that has received the most attention from adaptive dynamics theory is resource competition, yet there are few direct tests that competition for resources does cause phenotypic distributions to evolve. I used diversified populations of bacteria, and experimentally demonstrated that competition can cause ecological character displacement. Subsequently, I explored whether mutational bias for novelty can regulate adaptive radiation when ecological opportunities and selection were similar. I found an asymmetry in the extent and range of diversification among replicate populations initiated from different genotypes, suggesting that mutational bias can regulate adaptive diversification. Finally, I tested for resource specialization trade-offs by measuring the extent of variation in populations evolved in environments that range in complexity from one to three resources and found that diversity was not related to environmental complexity. Additionally, I explored the role of growth rate vs. yield trade-offs within and among populations that have diversified, and found little support for the hypothesis that these trade-offs underlie adaptive diversification in our bacterial populations. Together, these chapters test the predictions of adaptive diversification, so that we may better understand adaptive diversification in nature.Science, Faculty ofZoology, Department ofGraduat
Whiteflies and white lies: Dan Gerling's speculation on deceptive communication in parasitoid-host interactions
Get PDFWe used game theory to assess speculation from the late Dan Gerling that whitefly hosts might evolve to exploit the chemosensory system of their parasitoid natural enemies via fake (pseudo) marking pheromones. We considered three scenarios. Scenario 1 assumed parasitoid response to hosts was non-evolvable and hardwired. Here, we found that pseudo-marking was a viable strategy; values at fixation depended upon costs and benefits of marking. Scenario 2 assumed parasitoid host acceptance was non-evolvable and plastic. Here, we found that strong fake marking was common when parasitism was moderate, that is when the risk was high but parasitoids would tend to reject because good hosts were available. Scenario 3 assumed plastic parasitoids that could co-evolve with the host. Here, we found parasitoid sensitivity to host marks, at the population level, never stabilized. By contrast, fake host marking did stabilize but only at high signal strength when levels of parasitism were intermediate (i.e. 30–40%); when parasitism was more common, marks were ignored and hiding from enemies became more effective. We discuss the potential for evolution of pseudo-oviposition marks in the general sense with reference to sensory deception in non parasitoid-host systems.
Cite as: Roitberg, B.D. & Tyerman, J. 2018. Whiteflies and white lies: Dan Gerling's speculation on deceptive communication in parasitoid-host interactions. Israel Journal of Entomology 48 (2): 177–196. <published 14 September 2018>
DOI: 10.5281/zenodo.1418744
urn:lsid:zoobank.org:pub:84ABB648-496D-480E-8C53-1DD074EE9C8
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
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