1,721,148 research outputs found
Ecological coexistence of low-density populations of Apodemus sylvaticus and A. flavicollis (Mammalia: Rodentia)
No full textThe population size (estimated by POPAN method) and potential interspecific competition and spatial distribution in relation to vegetation features were studied in two sympatric and syntopic rodent species, Apodemus sylvaticus and Apodemus flavicollis. The study was performed by capture-mark-recapture study within a trap grid, at two adjacent forest sites in Mediterranean central Italy. We found that the population sizes of the two rodent species were comparatively lower than those recorded in conspecifics from other central Italian areas, and that the potential for interspecific competition was low at both sites, as revealed by the lack of negative correlations between the relative abundances of the two species after Monte Carlo analyses. The number of captures of both rodent species was not correlated to either the number of trees in each grid cell or the sum of tree diameters. The general implications of the obtained results are discussed
Country-based patterns of total species richness, endemicity, and threatened species richness in African rodents and insectivores
No full textCountry-based patterns of total species richness, endemicity, and threatened species richness in African rodents and insectivores are studied in this paper. We found several patterns which were similar between insectivores and rodents. Indeed, in both groups we observed: (i) a significantly uneven distribution of species richness across countries and geographic regions with highest species richness peaks being in Middle Africa and lowest peaks in Northern Africa, (ii) species richness increasing with rainfall but being independent on a country's surface area, (iii) in each country, the insectivore total species richness and endemic species richness increases were positively correlated with rodent total species richness and endemic species richness increases. However, number of endemics peaked in South Africa and D.R. Congo in both groups, but also in Tanzania for Insectivores and in Ethiopia for rodents. In addition, the highest numbers of threatened species occurred in D.R. Congo, Rwanda and Uganda for rodents and in South Africa, Tanzania and Cameroon for insectivores. The conservation implications of these results were discussed
Species richness and distribution of Neotropical rodents, with conservation implications
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Surveying an endangered saproxylic beetle, Osmoderma eremita, in Mediterranean woodlands: a comparison between different capture methods
No full textMeasuring population size is riddled with difficulties for wildlife biologists and managers, and in the case of rare species, it is sometimes practically impossible to estimate abundance, whereas estimation of occupancy is possible. Furthermore, obtaining reliable population size estimates is not straightforward, as different sampling techniques can give misleading results. A mark-recapture study of the endangered saproxylic beetle Osmoderma eremita was performed in central Italy by applying four independent capture methods within a study area where 116 hollow trees were randomly selected to set traps. Detection probability and population size estimates were drawn from each of these four capture methods. There were strong differences in detection probability among methods. Despite using pheromone and beetle manipulation, capture histories were not affected by trap-happiness or trap-shyness. Population size estimates varied considerably in both abundance and precision by capture method. A number of 0.5 and 0.2 adult beetles per tree was estimated using the whole data set by closed and open population models, respectively. Pitfall trap appeared the optimal method to detect the occurrence of this species. Since in the southern part of its distribution range, a single population of O. eremita is widespread in the landscape, and includes beetles from more than one hollow tree, conservation efforts should focus not only on preserving few and isolated monumental hollow trees, but should be extended to large stands
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
Spatial turnover and knowledge gap of African small mammals: using country checklists as a conservation tool
No full textComparing species checklists across countries can be important for determining the relative uniqueness of each country, which can be conveniently defined on the basis of the number of species occurring only in that country or, at most, in one of its neighboring countries. Production of accurate country checklists is complicated by the fact that, especially in scientifically neglected regions, the knowledge of the distribution of many species is unsatisfying. When distribution of a given species is insufficiently known, typically there may be apparent gaps in its distribution range. These species are defined here as 'gap species'. In this paper, we analyze the country checklists for rodents and insectivores of the African continent with the aims of (i) identifying the countries having a higher taxonomic uniqueness; (ii) highlighting countries where more research is needed; (iii) producing a list of gap species; and (iv) determining the ecological correlates of being a gap species. For both mammal groups, the important countries because of their low numbers of shared species were D.R. Congo, Cameroon, Sudan, Kenya, Tanzania, and South Africa. The countries with highest percentages of endemic taxa were Kenya, South Africa, Somalia and Tanzania for insectivores, and Ethiopia and South Africa for rodents. The number of gap species per country was 0-5 for both insectivores and rodents, with the only exceptions of Togo (12) and Benin (15). Apart from Togo and Benin, the main gap countries for rodents were Nigeria, Chad, Gabon, Burundi, and Rwanda, and for insectivores were Niger and Chad. In both groups, the number of gap species per country was independent on the country area, and both range and body sizes did not influence the probability for a species to have distribution gaps. However, most gap species were tropical forest inhabitants. The biogeographic and conservation implications of these data are discussed
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
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