1,721,037 research outputs found
Symbiotic bacteria inhabiting tephritid flies: a worldwide specific interaction
Full text linkSeveral insect lineages have evolved mutualistic associations with their symbiotic bacteria. This is the case of some members of Tephritinae, the most specialized subfamily of fruit flies (Diptera: Tephritidae), harboring co-evolved and vertically transmitted bacterial symbionts in their midgut, known as ‘Candidatus Stammerula spp.’. In the tephritid fly Bactrocera oleae, the major olive pest, symbionts are located in the oesophageal bulb, a diverticulum of the fly head, and designated as ‘Candidatus Erwinia dacicola’.
This research, based on two main studies, is focused on different aspects of the relationships between species of the family Tephritidae and their nonculturable symbiotic bacteria.
The first study investigated the presence of specific symbiotic bacteria in 15 of the 25 described endemic tephritids of the Hawaiian Archipelago, which represent a spectacular example of adaptive radiation, and their molecular relationships with symbionts of non-Hawaiian tephritids. Moreover the concordant evolution between host and symbiont phylogenies was tested. A specific symbiont was detected through PCR assays in all endemic individuals analyzed and it was designated as ‘Candidatus Stammerula trupaneae’ as it was included in Ca. Stammerula spp. monophyletic clade. The phylogeny of the insect host was reconstructed based on two regions of the mitochondrial DNA (16S rDNA and COI-tRNALeu-COII), while the bacterial 16S rRNA was used for the symbiont analysis. Host and symbiont phylogenies were then compared and evaluated for patterns of cophylogeny and strict cospeciation. Topological congruence between Hawaiian Tephritinae and their symbiotic bacteria phylogenies suggests a limited, but significant degree of host-symbiont cospeciation. The character evolution of three host traits, as island location, host lineage, and host tissue attacked, was finally reconstructed based on the symbiont phylogenies under the hypothesis of cospeciation.
The second study surveys the genetic variability of the olive fly symbiont, Ca. Erwinia dacicola, together with the patterns of genetic differentiation of B. oleae, over a large area of its geographical distribution, including most regions of the Mediterranean area, plus South Africa, California and Pakistan. Three bacterial haplotypes, showing a significative geographic distribution, were identified and the co-existence of different Ca. E. dacicola haplotypes in a single fly was never found. Our results reveal the presence of three symbiont haplotypes with a significant phylogeographic distribution related to the territory. In the Mediterranean populations only two bacterial lineages (htA and htB), previously recovered in Italian olive fly populations, have been found, showing a significative East-West genetic differentiation. The South African and Californian olive fly populations were represented only by one of these two lineages, respectively htA and htB. Moreover, a new haplotype (htC) was detected exclusively in the Pakistani population. On the other hand, a high degree of mitochondrial genetic variability with a substantial phylogeographic differentiation has been observed in the B. oleae populations analyzed, revealing the presence of 39 insect haplotypes. Symbiont and host haplotypes were then compared and a significant correlation was found suggesting the predominant presence of vertical transmission. Moreover, the bacterial haplotypes distribution seems to be more related to the territory than the numerous insect host haplotypes, representing an useful tool to reconstruct the debated olive fly’s historical origin
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
