1,720,988 research outputs found
Strong fitness differences impede coexistence between an alien water fern (Azolla pinnata R. Br.) and its native congener (Azolla rubra R. Br.) in New Zealand
No full textDespite considerable evidence that alien plants impact the fecundity, productivity and abundance of native plant species, support for alien plant species causing the widespread decline of native species is rare. Coexistence theory proposes that the outcome of competition between two species can be predicted through the invasion criterion, measured as a positive population-level growth rate of each competitor when that species is rare. Here we make use of coexistence theory to examine the likelihood of persistence of a native water fern (Azolla rubra) following invasion by an alien congener (Azolla pinnata) which has apparently displaced the native wherever their ranges overlap in New Zealand. We evaluate coexistence between the two water fern species using experimental measurements of population-level growth rates. We show that the alien A. pinnata has a higher fitness than A. rubra, which hinders coexistence between the two species. These experimental results match the rapid expansion of A. pinnata and the apparent decline of A. rubra observed in nature. Our study predicts that A. pinnata is capable of replacing its native congener, highlights the importance of fitness differences in invasion success, and demonstrates the value of experimental analyses of species coexistence for predicting longer-term invasion dynamics and impacts. Using experiments to test coexistence mechanisms between alien and native species is a valuable approach to predict invasion outcomes and one that can lead to insights on the long-term impacts of alien species, including extinction, on native species populations
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
Barriers to invasion: experimental analysis of mechanisms that prevent plant invasions in Hawaiʻi
Full text linkInvasive species are a serious threat to biodiversity and human well-being world-wide, yet why only a small proportion of introduced species become invasive is still poorly understood. Introduced plant success could be limited by barriers to 1) seed production, 2) dispersal, 3) germination, 4) seedling and juvenile survival and 5) growth. I investigated these barriers in 29 species, classified as invasive, casual escapees, or non-invasive in Hawaiʻi, belonging to three plant families (Acanthaceae, Apocynaceae, Bignoniaceae). I conducted three sets of experiments to examine these barriers: pollen viability staining and hand-pollinating species that do not regularly produce seeds, outplanting seeds at two field sites with and without competition and monitoring survival and growth of the resulting seedlings through one year, and growing seedlings in the lab to measure species traits. I found that 1. Four species had inviable pollen, as measured by pollen viability staining, and failed to produce seeds. Calotropis gigantea (crownflower) produced seeds only when hand-pollinated, indicating that natural seed set is prevented by the lack of a pollinator. 2. Lack of dispersal mutualists limits the success of one species, and possibly two additional species. 3. Germination was not a barrier for any of the species studied. 4. Competition with the naturally-assembled plant community reduced survival in some non-invasives or casuals. Damage from herbivores in the field was correlated with lower survival of some species in the Acanthaceae and Bignoniaceae, but not the Apocynaceae. 5. Seedlings of invasive species grown in pots had significantly higher RGR and photosynthetic rates than non-invasives. In field seedlings, invasives had higher RGR, greater specific leaf area in the absence of competition, and, in the presence of competition, higher photosynthetic rates. 6. Three species in this study, though currently not invasive, had no demonstrable barriers to invasion. These studies are some of the first to explicitly document barriers to introduced plant success, by comparing phylogenetically controlled invasive and non-invasive ornamental plants in the introduced range. My work contributes to our understanding of invasions by documenting previously hypothesized, but poorly tested, barriers associated with missing mutualists, biotic resistance due to competition, and species traits.Ph.D
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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