1,720,954 research outputs found
Influence of male mating history on female reproductive success among monandrous Naryciinae (Lepidoptera: Psychidae)
No full text1. Multiple male copulations can have detrimental effects on female fitness
due to sperm limitation. 2. Monandrous Naryciinae females are immobile while the males are
short-lived and do not feed. Multiple male mating is therefore expected
to lead to sperm limitation in females. Sperm limitation and male
limitation are hypothesised as causes of the repeated evolution of
parthenogenetic reproduction in the Psychidae.
3. In this study, the effects of multiple male mating on female
reproduction are investigated in several species of Naryciinae by
allowing males multiple copulations. The results for two species,
Siederia listerella and Dahlica lichenella, are compared. The sex ratios
of 53 natural populations are examined for indications of male
limitation.
4. Previous copulations by the male increased the female's risk of
remaining unfertilised. However, contrary to expectations, those
unfertilised females were capable of successful re-mating.
5. In S. listerella, the number of previous copulations of males
negatively influenced female fitness. Females produced 30% fewer
offspring if they mated with a previously mated male. In D. lichenella,
the older the male and the lower its number of total lifetime
copulations, the higher the female's reproductive success.
6. Only a fraction of the investigated populations had a female-skewed
sex ratio, but differences in development time between males and females
could lead to reproductive asynchrony.
7. In conclusion, male mating history did not lead to strong sperm
limitation in Naryciinae as had been suggested by their life history
Investigating the origin of parthenogenesis and ploidy level in Dahlica fennicella (Lepidoptera: Psychidae)
No full textThe theories for the predominance of sexual reproduction predict that parthenogens should have no long-term evolutionary potential due to the lack of genetic recombination, despite short term advantages. Although parthenogenesis is rare among high order animals, true parthenogens can be found in various taxa. The intriguing question of the proliferation and persistence of parthenogenetic species needs investigation. An ideal species for such research is a parthenogenetic mont Dahlica fennicella that appears to be as equally successful as other coexisting sexual species. We investigated whether high ploidy level of D. fennnicella is due to hybridization between closely related sexual species. The results form flow cytometry measurements confirmed that D. fennicella is exclusively tetraploid whereas all sexual species of the genera Dahlica and Siederia are diploid. Our phylogenentic results showed the non-hybrid origin of the parthenogenetic D. fennicella in this group of Lepidoptera. Most likely, the parthenogenetic D. fennicella orginated by autopolyploidization of D. lazuri, which is one of its closely related sexual species. We suggest that the apparent evolutionary success of D. fennicella might be due to polyploidy that could mask deleterious mutuations and probide greater levels of genetic variations.peerReviewe
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
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