1,721,019 research outputs found
Causes and consequences of phenotypic plasticity in body size: The case of the yellow dung fly scathophaga stercoraria (diptera: scathophagidae)
No full textPhenotypic plasticity occurs when a particular genotype assumes different phenotypes depending on its environment. In this article, I focus on phenotypic plasticity in body size and associated life history traits, primarily growth rate and development time, thus taking a trait-centered view. First, I discuss and review phenotypic plasticity in body size in insects in general, centering on its environmental causes and its behavioral and fitness consequences. Plasticity in body size can be caused by a variety of environmental variables, most notably food availability, predators, temperature, season length, photoperiod and humidity, producing recurrent patterns. Food limitation generally results in small body sizes. High temperatures often result in rapid growth but smaller body sizes (Bergmann’s and the temperature-size rule). Short growing seasons limit growth and thus final body size, particularly in species with long development (the converse Bergmann rule). This is often proximately mediated by photoperiod. Predators also limit foraging and hence growth and final body size of prey species, and sometimes induce particular morphological adaptations (induced defenses). For an evolutionary ecologist, the central question is whether or not the phenotypic plasticity exhibited is adaptive. This requires demonstration of heritable variation of the trait and the existence of environment-specific fitness trade-offs. Based on these criteria, growth and body size plasticity in response to seasonal constraints and predators can often be shown to be adaptive, while size reductions due to food limitation typically represent merely the ‘best of a bad situation’. Whether temperature-mediated size plasticity (i.e., Bergmann’s rule) is adaptive remains unclear and contended.
Plasticity in adult body size influences plasticity in adult behavior. Small individuals are forced to use particular strategies in order to overcome their handicap and successfully compete against larger conspecifics to augment their fitness. This is most prominently seen in species with discrete sizedependent alternative foraging or reproductive strategies, but equally necessary when body size variation is continuous. Again, the question is addressed whether small size is merely the ‘best of a bad situation,’ or whether there are environments in which small individuals can match the fitness of larger conspecifics, in which case small size would be adaptive. Evidence suggests that in most cases it is the former. Behavioral plasticity can be classified according to the proximate mechanism, time scale, frequency of occurrence, and the variance component where variation may be detected. In the second part of this chapter, I present a long-term case study of phenotypic plasticity in body size and associated traits of the yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae). I discuss various environmental causes and behavioral consequences, and conclude that although the extent of body size plasticity of yellow dung flies may not be untypical, the degree of adaptive plasticity perhaps is unusually high. This may be related to the particular ephemeral larval habitat (cow dung), the occurrence and size of which is variable and unpredictable in space and time. Furthermore, high adult mobility promotes extensive gene flow, preventing local adaptation of populations. Long-term case studies of diverse species well suited for this purpose will elucidate which specific conditions foster the evolution of adaptive plasticities, be they morphological, life history, physiological or behavioral
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
Density-dependent prophylaxis in insects.
No full textParasites and pathogens are a ubiquitous threat facing all organisms. Life history theory predicts that if investment in parasite resistance mechanisms is costly (as suggested by numerous studies), then organisms should tailor their investment in them to match their perceived risk of infection. Because most parasites are transmitted in a positively density-dependent manner, the threat from parasites tends to increase as population density increases. As a result, it is predicted that organisms should use population density as a cue to the risk of becoming infected and should increase investment in disease resistance mechanisms as the degree of crowding increases—this is known as density-dependent prophylaxis (DDP). This phenomenon has been experimentally tested in a number of insect species, and in most cases support for the DDP hypothesis has been forthcoming. DDP is likely to be particularly prevalent in species exhibiting density-dependent phase polyphenism (i.e. the phenotype adopted by the insect is plastic and dependent on the population density it experiences during its early development). We discuss the hormonal and genetic mechanisms underlying phase polyphenism and DDP, and speculate on the circumstances leading to their evolution. We end by discussing how future research into DDP might develop
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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