1,722,468 research outputs found
Species-area relationships underestimate extinction rates
Full text linkCopyright © 2012 Elsevier Masson SAS. All rights reserved.The species-area relationship (SAR), i.e. the increase in species number with area, has been repeatedly used to predict species extinction, at both local and global scales, with habitat reduction. He and Hubbell (Nature, 2011; 473, 368–371), however, argued that the function that relates species loss with decreasing habitat area cannot be simply obtained reversing the species-area accumulation curve. Using a statistically more appropriate curve based on endemics (EAR), they concluded that the SAR overestimates species extinction. Although we agree that SARs and EARs have different shapes, this does not imply that SARs overestimate species extinction. Empirical evidence suggests that SARs do not overestimate, but underestimate species extinction by habitat loss and fragmentation. We discuss various examples taken from recent literature to show that SARs underestimate species extinction
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
FIGURE 2. Tarphius isabelae Serrano & Borges n in A new species of Tarphius Erichson, 1845 (Coleoptera: Zopheridae) from North Africa and notes on an Iberian species
No full textFIGURE 2. Tarphius isabelae Serrano & Borges n. sp., female genitalia (ventral view).Published as part of Serrano, Artur R. M., Amorim, Isabel R. & Borges, Paulo A. V., 2013, A new species of Tarphius Erichson, 1845 (Coleoptera: Zopheridae) from North Africa and notes on an Iberian species, pp. 493-500 in Zootaxa 3613 (5) on page 496, DOI: 10.11646/zootaxa.3613.5.5, http://zenodo.org/record/21683
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
Using species abundance distribution models and diversity indices for biogeographical analyses
Full text linkWe examine whether Species Abundance Distribution models (SADs) and diversity indices can describe how species colonization status influences species community assembly on oceanic islands. Our hypothesis is that, because of the lack of source-sink dynamics at the archipelago scale, Single Island Endemics (SIEs), i.e. endemic species restricted to only one island, should be represented by few rare species and consequently have abundance patterns that differ from those of more widespread species. To test our hypothesis, we used arthropod data from the Azorean archipelago (North Atlantic). We divided the species into three colonization categories: SIEs, archipelagic endemics (AZEs, present in at least two islands) and native non-endemics (NATs). For each category, we modelled rank-abundance plots using both the geometric series and the Gambin model, a measure of distributional amplitude. We also calculated Shannon entropy and Buzas and Gibson's evenness. We show that the slopes of the regression lines modelling SADs were significantly higher for SIEs, which indicates a relative predominance of a few highly abundant species and a lack of rare species, which also depresses diversity indices. This may be a consequence of two factors: (i) some forest specialist SIEs may be at advantage over other, less adapted species; (ii) the entire populations of SIEs are by definition concentrated on a single island, without possibility for inter-island source-sink dynamics; hence all populations must have a minimum number of individuals to survive natural, often unpredictable, fluctuations. These findings are supported by higher values of the a parameter of the Gambin mode for SIEs. In contrast, AZEs and NATs had lower regression slopes, lower a but higher diversity indices, resulting from their widespread distribution over several islands.We conclude that these differences in the SAD models and diversity indices demonstrate that the study of these metrics is useful for biogeographical purposes.info:eu-repo/semantics/publishedVersio
Sympherobius Banks, 1904, a new hemerobid genus for the Azorean archipelago (Neuroptera: Hemerobiidae )
Full text linkSympherobius Banks, 1904 (Neuroptera: Hemerobiidae) is recorded for the first time for the Azorean archipelago. The Azorean Neuroptera fauna is now composed by eight species and five genera belonging to two families
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