1,721,054 research outputs found
Ecomorphology of morpho-functional relationships in the family of Sparidae: a quantitative statistic approach
No full textIn many fish species, morphological similarity can be considered as a proxy for similarities in habitat use. The Sparidae family includes species that are recognized for common morphological features such as structure and positioning of the fins and specialized dentition. The aim of this study was to quantitatively describe the relationship of body shape morphology with habitat use, trophic level, and systematics in the majority of known Sparidae species (N = 92). This ecomorphological comparison was performed with a geometric morphometric approach considering as variables the Trophic Index (TROPH), the habitat (i.e., classified as demersal, benthopelagic and reef associated) and the phylogenetic relationship of species at the subfamily level. The analysis by the TROPH variable showed a positive relation with shape because the morphological features of all the species are strongly correlated with their trophic behavior (e.g., herbivore species have a smaller mouth gap that make them able to feed upon sessile resources). The morphological analysis according to the Habitat variable was used to classify species according to a feeding-habitat niche in terms of portion of the water column and seabed space where species mostly perform their behavioral activities. We described three kinds of morphological designs in relation to a benthopelagic, demersal and reef-associated habit. The six subfamily groups were morphologically well distinguishable and the cladogram relative to Mahalanobis' morphological distances was compared with those proposed by other authors. We also quantified the phylogenetic relationship among the different subfamilies based on the analysis of shape in relation to trophic ecology, confirming the observations of the authors
Ontogenetic and environmental effects on otolith shape variability in three Mediterranean European eel (Anguilla anguilla, L.) local stocks
Full text link7 pages, 4 figures, 3 tablesOtolith morphology is an efficient tool for the discrimination of fish stocks, populations and species when comparative genetic data are not available. Currently, the relationship between environmental factors and otolith shape is poorly characterized for the European eel (Anguilla anguilla), a highly migratory catadromous species constituting a single, randomly mating stock. The present study analyses the differences in otolith morphology between three Mediterranean eel local stocks from different environmental contexts (i.e. two brackish lagoons and one river). The relationship between otolith shape and otolith size was studied by means of Elliptic Fourier analysis and multivariate statistics. Otolith profile was digitally acquired and Cartesian coordinates were extracted. Partial Least Square (PLS) analysis pointed to continuous allometric growth in size and shape in otoliths from all three sites. In the three environments, shape variations occurred during growth as indicated by the presence of a significant and positive relationship between otolith size and the first PLS latent vector (i.e. which bears most of the information regarding otolith outline). Differences between smaller and larger sized otoliths were investigated using PLS Discriminant Analysis (PLSDA) and cluster analysis. Results indicate that otolith shape is highly uniform at smaller than at larger sizes. These shape differences apparently overlap the initial differentiation of the small otolith outlines acquired by eels during the growing phase as elvers in the marine environment. Data were discussed considering that the physical and chemical habitat variability in brackish lagoons and river could underlie a marked change in otolith shape during the animals' growthThe present work was funded by a grant from the Ministry of Research and University to EC within the PRIN 2006 Project “An Integrated
Approach to the Conservation and Management of the European Eel in the Mediterranean Region” (Coordinator Prof. G. De Leo University of Parma); themorphological approach was developed within the framework of the project HIGHVISION (DM 19177/7303/03) to PM. The authors wish to thank the fishermen's associations of the river Tiber, Caprolace and Lesina for their help during samplings. Aguzzi J. is a Postdoctoral Fellow within the Ramon y Cajal Program (MICINN, España)Peer reviewe
Global deep-sea biodiversity research trends highlighted by science mapping approach
Full text linkThe scientific literature available on deep-sea biodiversity is ample and covers a wide array of objectives, geographic areas, and topics. It also explores the links between ecosystem functioning and productivity as well as modeling, management, and exploitation. New statistical analytical tools now allow the comprehensive monitoring of the status of deep-sea research to highlight global research topics and their trends, which deserve further development and economic investments. Here, we used a science mapping approach to provide a global and systematic bibliometric synthesis of these current research topics and their trends to identify the size, growth, trajectory, and geographic distribution of scientific efforts as well as to highlight the emerging topics. A total of 1287 deep-sea biodiversity publications were retrieved from the Scopus database from 1993 to the present. Both established and emerging research topics were identified: (i) biogeochemical, microbial, and molecular analyses; (ii) biodiversity assessments; (iii) ecosystem conservation and management; and, finally, (iv) zoology and taxocoenosis. The temporal change in research activity (which was assessed by subdividing publications into blocks from 1993 to 2010 and 2011 to 2019) demonstrated that the “biogeochemical, microbial, and molecular analyses” cluster was not present from 1993 to 2010 since it was included in the cluster for “biodiversity assessments,” which it eventually diverged from in the following couple of decades. The United States took the dominant role in research, followed by the United Kingdom; Germany and France were also evidenced. China was particularly associated with the United States
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
Light and Shape: A Contribution to Demonstrate Morphological Differences in Diurnal and Nocturnal Teleosts
No full text11 pages, 5 figures,1 table.Light intensity is an important environmental
factor affecting the structure of fish assemblages
during the day–night cycle. Light influences how organisms
perceive their environment, modulating their intraspecific
and interspecific relationships. The relationship
between light intensity variations and biological cycles
should be observed at the level of organismal morphology.
In this study the relationship between activity
rhythms, thus light intensity experienced by fish in the
period of major activity and external morphology, have
been investigated. The morphological traits of 97
selected fish species were compared in order to determine
the existence of a common morphological plan in
agreement with their diurnal or nocturnal activity
rhythm. Species sorting was performed by maximizing
the diversity of activity rhythm, habitat choice, ecology,
and trophic habits within the same family, to assess the
importance of the day–night cycle on species morphology
in relation to other environmental features. The morphological
characters selected for the geometric morphometric
analysis were body profile and the position of mouth,
eye, pelvic, pectoral, dorsal, and caudal fin. The present
analysis allowed different consensus forms for nocturnal
and for diurnal species to be identified. Two-block Partial
Least Squares analysis was then performed for the
purpose of modeling the covariation between the form
and two important external variables (ecology and activity).Ministero Italiano per le Politiche Agricole
e Forestali; Contract grant number: Law 41/82.
J. Aguzzi is a postdoctoral fellow
(Programa Juan de la Cierva), sponsored by Ministerio
de Educacio´n y Cultura, Espa˜na.Peer reviewe
- …
