1,720,980 research outputs found
Analysis of the cox2-3 spacer region for population diversity and taxonomic implications in rhodolith-forming species (Rhodophyta: Corallinales)
No full textCoralline red algae demonstrate phenotypic plasticity related to environmental factors, rendering their identification difficult. The cox2-3 spacer is a mitochondrial marker widely used for phylogeographic studies and discrimination between closely related species in red algae; however, cox2-3 spacer sequence data for coralline algae are still limited. In this study we substantially increase the number of cox2-3 spacer sequences available for coralline algae, exploring their usefulness for different types of molecular investigations in coralline algae (DNA barcoding and phylogeography), with emphasis on rhodolith-forming species. Specimens from North Atlantic Europe, the Caribbean region and the Gulf of California (Mexico) were sequenced and two datasets were built, one for the subfamily Lithophylloideae and one for the Melobesioideae. Our results suggest the utility of cox2-3 spacer as barcoding marker for coralline algae with a slight variation in the barcode gap depending in the way gaps in the alignment are treated. Analyses on both datasets found a barcode gap or separation between intra and interspecific divergence (p distance and ABGD analysis) while some inconsistencies were evident when the results were compared with morphology-based classification. Using the cox2-3 spacer region, the morphospecies Lithophyllum margaritae from the Gulf of California revealed the existence of two well-supported clades, with the possibility of respectively five and two additional species; haplotype networks for Phymatolithon calcareum and P. purpureum revealed similar patterns when Mediterranean and NW Europe specimens were analysed, and P. calcareum was shown to consist of a single population in NW Europe. Based on our analyses the marker cox2-3 spacer has strong potential applications for studies of phylogeography and DNA barcoding in coralline algae after understanding its variation
Phylogeny of maërl-forming corallines (Corallinales, Rhodophyta), with emphasis on Irish species
No full text
Studies on maerl/rhodolith-forming species (Corallinales: Rhodophyta): a molecular perspective of their diversity
No full textRiassunti della riunione scientifica annuale del Gruppo di Lavoro per l'Algologia della Società Botanica Italiana (Ancona, 4-5 Novembre 2011) - Abstrac
Reassessment of branched Lithophyllum spp.(Corallinales, Rhodophyta) in the caribbean Sea with global implications
No full textPlastid-encoded rbcL and psbA sequences from branched, Caribbean Sea Lithophyllum specimens indicate that
four species are present, not one. Short (263 base pairs) rbcL sequences from an isolectotype of L. kaiseri (Gulf of Suez)
and the holotypes of L. congestum, L. daedaleum and L. platyphyllum (Caribbean Sea) show that L. congestum and L.
daedaleum are conspecific with L. kaiseri, the last having nomenclatural priority. Lithophyllum platyphyllum, currently
considered a synonym of L. congestum, is recognised as a valid species. Lithophyllum stictaeforme, originally described
from the Mediterranean Sea, is not conspecific with L. kaiseri (as L. congestum) as previously suggested. Lithophyllum
neocongestum sp. nov. and L. pseudoplatyphyllum sp. nov. are proposed. Together with L. platyphyllum, these three
branched species are so far endemic to the Caribbean Sea. This is the first report, documented by DNA sequence data, of
a coralline species (L. kaiseri) widespread through the tropical Indo-West Pacific Oceans, Red Sea and Caribbean Sea
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
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