1,721,018 research outputs found
Integrative Taxonomy: A study on some of Victoria Land’s Antarctic mite species
Full text linkThe extremely inhospitable Antarctic ecosystems confine plants and invertebrates to sparse and restricted ice-free areas. These species survived for millions of years in isolated refugia where population divergence and differentiation can occur, potentially resulting in speciation. The limited dispersal abilities of invertebrate species combined with their specific habitat requirements and the substantial geographical barriers can drastically reduce the gene flow between different populations, resulting in high genetic differentiation between clusters of individuals. With more than 100 described species, mites are surely the most diverse invertebrate group of Continental Antarctica. Among them, the free-living genus Stereotydeus Berlese, 1901 (Acari: Prostigmata) is represented by 6 Antarctic species of which 5 occur along the coastal zones of Victoria Land and the Transantarctic Mountains. In order to examine the biodiversity and the phylogeographic distribution ranges of Stereotydeus spp. across Victoria Land, I conducted an integrated analysis of the genus through phylogenetic, morphological and population genetics studies on specimens collected from nine localities in Victoria Land. I sequenced the second part of the cytochrome c oxidase subunit I mitochondrial gene (cox1) and a fragment of the 28S ribosomal RNA-encoding gene using mite-specific primers. I morphologically identified and described two novel Stereotydeus species from central and south Victoria Land. While the relationships between the cox1 haplotypes from North Victoria Land are well defined, the distribution of the central-southern species appears more complex. This suggests a possible common evolutionary history in many isolated glacial refugia, with scarce gene flow even within populations probably resulting from inter/intra-specific events influenced by several abiotic/biotic factors. Recent threats to Antarctic biodiversity like accelerated climate change, pollution, biological invasions and the increase of human activities have caused increased calls for adequate conservation measures. Establishing a new distribution map for the Stereotydeus species of Victoria Land may help lay the foundations for future decisions in matters of protection and conservation of the unique terrestrial fauna of Antarctica
Cooperative defence of female chamois successfully deters an eagle attack
No full textIn mountain ungulates, antipredator behaviour is one of the main constraints on foraging behaviour and habitat selection, especially when newborn, vulnerable offspring are present. Golden eagles have been known to prey on ungulates successfully, but predation may be rela- tively rare on chamois. Here, we report an unsuccessful predation attempt by a golden eagle on a kid of Apennine chamois. The kid was grazing in a female kid mixed herd, and the attack by the eagle was deterred by cooperative defence of females. Chamois are a social species: defend- ing other females’ fawns may be consistent with the impor- tance of cooperative maternal behaviour in kin groups
The role of age and maturation on jump performance and postural control in female adolescent volleyball players over a season
No full textBackground Jump performance and postural control are essential for success in technical/tactical actions and overall playing performance in volleyball. Youth athletes undergo significant physical and neuromuscular development during adolescence, which can impact these abilities. This study examined the effect of age and biological maturity, assessed as the distance from peak height velocity using the maturity offset (MO), on vertical and plyometric jumping abilities and postural control in adolescent female volleyball players across different age categories throughout a competitive season. Methods Forty-five adolescent volleyball players (aged 12.5 to 17) from four age categories (U13, U14, U16, U18) of the same club participated in three testing sessions during a season. Jump performance was assessed through countermovement (CMJ) and drop jump (DJ) tests, while postural control was measured using a static balance task. All tests were conducted using force plates, sampling at 1000 Hz (for jumps) and 100 Hz (for static balance test), to study force-related and CoP outcomes, respectively. MANCOVA models were applied for each assessment to examine the effects of age category and season timepoint on selected performance variables, including MO as a covariate to account for the maturation effect. Follow-up univariate and linear regression models were performed in case of significance from the multivariate analysis. Results MO significantly differed among all the age categories and session timepoints (p < 0.001). CMJ multivariate analysis revealed significant results regarding the session (p = 0.010, eta(2)(p) = 0.49) and MO (p = 0.025, eta(2)(p) = 0.29) effects, but not for age category (p = 0.165) or age category x session interaction (p = 0.152). Conversely, DJ and postural control showed no significant results for any studied effect. The session timepoint had a significant effect on the CMJ concentric impulse, while MO was significantly positively associated with peak power, jump momentum, concentric impulse, and eccentric impulse (p < 0.001, R-2 = 0.31-0.57). Conclusions The results emphasize the specific influence of biological maturation on power and force production during vertical jumps, while other specific plyometric and postural control adaptations seem to be less sensitive to chronological age and maturational changes during the adolescence period in female volleyball players
Reliability of Molecular Sex Identification in the Adélie Penguin (Pygoscelis adeliae) from DNA-Poor Samples
No full textSex identification is crucial for behavioral, ecological and conservation studies. In monomorphic bird species, traditional methods for sex assessment require potentially invasive sampling and manipulation of individuals, such as through cloacal examination. Thus, molecular methods involving non-destructive sampling are needed to reduce the stress of animals under study. In monomorphic Adélie penguins (Pygoscelis adeliae), the use of a penguin-specific primer pair (PL/PR) to identify sex has been evaluated through DNA extracted from nondestructive feather samples. With penguin-specific primers for the CHD1 gene found on the sex chromosomes, we efficiently identified the sex of all sampled individuals (n = 92, belonging to 46 complete nesting pairs in study colonies; n = 26 belonging to surveyed individuals in a control colony). DNA extraction and PCR protocols to improve amplification success are reported. Our results were also confirmed through Sanger sequencing used to determine the previously unpublished sequences of the CHD1 alleles in Adélie penguins, which were subsequently deposited in GenBank and used to compare to similar species. In phylogenetic reconstructions, CHD1Z and CHD1W sequences of the Adélie Penguin grouped together with other Pygoscelis and were the sister group of Spheniscus and Eudyptes genera
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
- …
