1,720,975 research outputs found
Another piece of the evolutionary history of Atlantic skates (Chondrichthyes, Rajiformes ): integrating DNA barcoding approach and phylogenetic inferences
No full textConservation and long-term management plans of marine species need to be conceived upon a universally recognised key-feature: species identity. This important assignment resulted particularly arduous among skates (order Rajiformes), in which the phenotypic similarity between some taxa and the individual variability in others, entangled accurate species identification.
This study confirms the power of DNA barcoding for the discrimination between skate species across the Atlantic Ocean and for its use as effective tool to minimize the risk of species misidentification and to elucidate species boundaries. In this perspective, this work compiles and establish a new fully available and well-curated barcode library, the ELASMO-ATL project, which gathered biological and molecular information of 432 skate specimens and covered coastal waters of four FAO Major Fishing Areas (27, 34, 47, 41) of the Atlantic Ocean.
The evolutionary histories of 34 skate species were estimated with two concatenated mitochondrial markers (COI and NADH2) through Bayesian and species level phylogeny analyses. It was possible to discover a new evolutionary lineage within the genus Raja in the southern-most part of its distribution area and to enable deepening the relationship between South-African endemic species of Rajella. Once again, Western South African coasts and oceanographic fronts may play a fundamental role among skates’ speciation events in which the paleoclimatic and paleogeographic history joined to hydrography events could have contributed to the formation of refugial areas, characterised by geographical isolation. Subsequent contact zones in these areas between Senegal and Angola seems to constitute a continuum/cline of genetic change among some Raja species.
These data successfully resolved many taxonomic ambiguities and demonstrated a highly cohesive monophyletic clustering among the order laying the foundations for further inference of evolutionary patterns suitable for addressing management and conservation issue
Historical ecology of the Mediterranean population of the Great White Shark, Carharodon Carcharias, from museum collection
No full textThe Great White Shark, Carcharodon carcharias, is Critically Endangered in the Mediterranean due to its low population density and the absence of
conventional aggregation sites, hampering data collection and reconstruction of the population behavioral ecology. Historical collections, being a repository of past biodiversity, can overcome these issues for a better understanding of fundamental processes such as paleo-ecological changes. In this perspective, this work deals with the historical ecology of the Mediterranean white shark population through a multi-element analysis of stable isotopes (carbon, nitrogen, zinc, and strontium) of 5 historical remains archived in Italian museums and private collections. Using individual vertebrae (N = 4), we provide information about the ontogenetic shifts and the trophic ecology by the estimate of the isotopic composition of carbon, nitrogen, and zinc from the vertebral collagen, and date back one fossil tooth using strontium isotope
composition. The main results show that: 1) isotopic values of nitrogen confirmed the white shark as a top predator, 2) the diet is based on dolphins and fishes, 3) the zinc analyses revealed a strong difference between the pre-birth and post-birth isotopic composition 4) the dating of the fossil tooth confirmed the Miocene-Pliocene presence in the Mediterranean. Overall, these multi-element isotope approaches have the potential to obtain important information on developmental physiology, ecology, and behavior of the poorly studied Mediterranean white shark, highlighting the fundamental role of historical remains for an overall knowledge of shark life-history, avoiding invasive sampling and analysis
Molecular identification of endangered marine predators by barcoding ancient museum rostra of Mediterranean sawfish populations (Chondrichthyes, Pristidae)
No full textBackground: A growing concern in conserving threatened animals affected by human impact has been significant worldwide. Among marine animals, sawfishes (Chondrichthyes, Pristidae) are considered one of the most endangered families among
lasmobranchs, resulting in extinction in many coastal areas around the world, including the Mediterranean Sea. Here, sawfish
ccurred with two species, Pristis pristis and P. pectinata, until the second half of the last century and are now considered Critically
ndangered/Possibly Extinct. The historical occurrence of sawfish in the area is documented by bibliographic/ archival records and y numerous preserved historical rostra available in museum collections. In this study we attempted to genetically characterize the
istorical remains of sawfish from several European museums and to enable the investigation of their evolutionary and ecological relationships with global samples.
Results: A total of 80 rostra specimens, dated from 1700 to 1900 and catalogued as unknown origin or Mediterranean (11), were collected from 11 European museums and were properly prepared for ancient DNA genetic analysis. Taxonomic identification at the species level was obtained through PCR amplification of small fragments (150 bp) of two mitochondrial markers commonly used for species identification (i.e., the mitochondrial COII and the NADH 2). Sequence comparison with currently available ones from public repositories and phylogenetic tree analyses indicated that the historical specimens belonged to four species, P. pristis, P. zijsron, P. pectinata, and Anoxypristis cuspidate, with a high frequency of mismatches (69%) between molecular identification and species museum cataloguing, when present. These preliminary data also showed the presence of two sequence sub-clusters in the poorly barcoded species P. zijsron.
Significance: With the expansion of this initial analysis, we will contribute to increase the limited
olecular data of these critically endangered large predators and to exploit historical genetic data for reconstructing phylogenetic/phylogeographic extent of the possibly extinct population of Mediterranean sawfish
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
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