1,721,179 research outputs found
Phenotypic Integration of Sexually Selected Traits in a Songbird
Full text linkThesis (PhD) - Indiana University, Ecology and Evolutionary Biology, 2007Natural selection favors traits that fit not only the external environment, but also the internal environment of the organism. As a consequence, traits often show a pattern of correlation, or phenotypic integration. In this dissertation, I examined both the evolutionary processes and the physiological mechanisms that generate phenotypic integration. I studied a natural population of a songbird, the dark-eyed junco (Junco hyemalis), focusing on the male "mating phenotype," the suite of morphology, physiology, and behavior used to attract and compete for mates. In Chapter 1, I review literature suggesting that correlational selection, which occurs when traits interact in their effects on fitness, may have effects on the physiological mechanisms that underlie integrated suites of traits. In Chapter 2, I found that correlational sexual selection favored an association between body size and a white patch on the tail feathers ("tail white"), an ornament used both in courtship and male-male competition. I also found that body size and tail white were genetically correlated. These results suggest that correlational selection may maintain the integration of the two traits. In Chapters 3-5, I focus on the role of the steroid hormone testosterone in the mating phenotype. In Chapter 3, I measured natural variation in testosterone levels and found that more attractive males had higher androgen responsiveness. That is, males with more tail white produced more testosterone in response to an injection of GnRH, a hypothalamic hormone. This suggests that investment in mating behavior (which seems to be controlled by testosterone) may covary with attractiveness. Indeed, in Chapter 4, I found that androgen responsiveness naturally covaries with both mating and parental behavior. Males that produced more testosterone defended their territories more vigorously and fed their offspring less often. Finally, in Chapter 5, I examined how selection acts on androgen responsiveness, and found that males with very high or very low responsiveness were less likely to survive. Combined, these studies suggest that testosterone, on a physiological level, and correlational selection, on an evolutionary level, act as integrators of the male mating phenotype
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
How Parasites Affect, and are Affected by, Host Physiology, Behavior, and Breeding System
Full text linkThesis (Ph.D.) - Indiana University, Biology, 2017Parasites comprise a striking diversity of lifeforms, and probably evolved from free-living organisms many times. It has even been argued that most species on earth are parasites. Parasites can have profound effects on their hosts, and the biology of hosts, in turn, affects the evolution and spread of parasites. My dissertation research examined the effects of parasites on the physiology, behavior, and breeding systems of their hosts, as well as the effects of host physiology and behavior on parasitism. In chapters one and two, I focused on the disease ecology of a natural system: haemosporidian (blood) parasites and an avian host, the dark-eyed junco. In chapter one, I measured the association between junco long-distance migration behavior and infection with haemosporidian parasites. I found that a migrant population of juncos maintains a significantly lower prevalence of haemosporidian parasite infections relative to a closely related and seasonally sympatric sedentary junco population, suggesting that longdistance host migration may be associated with reduced parasitism. In chapter two, I showed that experimental elevation of circulating testosterone levels in hosts does not affect the prevalence of haemosporidian parasite infections in a wild population of juncos, and that haemosporidian infections do not affect host telomere degradation. I also showed that the prevalence of haemosporidian parasite infections increases with host age. In chapters three and four, I used an experimental host-parasite system in the lab to assess how coevolving parasites affect the breeding system of their hosts. In chapter three, I showed that coevolving bacterial parasites (Serratia marcescens) can constrain the spread of self-fertilization into obligately outcrossing populations of nematode (Caenorhabditis elegans) hosts. This result supports the Red Queen hypothesis and contributes to a large body of evidence that antagonistic coevolution between hosts and parasites can maintain biparental sex. Finally, in chapter four, I showed that the presence of parasites (S. marcescens) in the environment does not induce plastic changes in the propensity to outcross in hosts (C. elegans) capable of both outcrossing and self-fertilization, and that coevolutionary interactions with S. marcescens parasites does not cause C. elegans hermaphrodites to evolve a higher propensity to outcross
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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