1,721,038 research outputs found
Riconosci le macchie: foto-identificazione del tritone crestato (Triturus carnifex) usando I3S Pattern
No full textIn recent decades, amphibian populations were subjected to a progressive worldwide decline. As a result, several studies monitored and studied the dynamics of the population, in an attempt to counteract this trend. Many studies need capture-mark-recapture sessions, in order to estimate key parameters such as the numerical abundance, the density, the phenology, and to collect biological samples and biometric data. In such researches is needed the unique identification of each individual, a fundamental requirement for a correct interpretation of the collected data. Over the past few decades, several techniques have been designed and improved to identify amphibians. Some, such as the toe-clipping, although widely used, have been repeatedly criticized over the years, as potentially harmful to the populations under study. Thanks to the considerable computing power offered today by modern computers, in recent years the photo-identification has arisen as a tool for individual identification. It comprises diverse set of software and techniques that help the operator to identify the captured individuals. We present the results of a medium-term study of a population of the Italian crested newt (Triturus carnifex) in which individuals were photo-identified with sight and with the help of the free software I3S Pattern. The software requires the identification of three reference points to superimpose the images and then proceeds to the automatic extraction of the interest points using the OpenCV version of the SURF algorithm. The software was able to correctly recognize all individuals, both in the test run, both in the subsequent field validation. The efficiency, gratuity and ease of use, make I3S Pattern a useful tool for the individual identification in case of studies involving a large number of animals
Differenze di nicchia termica tra i morfi cromatici di Podarcis muralis
No full textThe co-occurrence of different morphs within the same population represents an intriguing challenge for evolutionary biologists, since their maintenance should be associated to the coexistence of alternative adaptative strategies. In this scenario, the common wall lizard (Podarcis muralis) exhibits a typical chromatic polymorphism in ventral colouration (red, R; white, W; yellow, Y) which has been already associated to physiological and ethological differentiation. Here we investigate if the three morphs show also ecological differences with respect to the thermal microhabitat conditions, which may play a crucial role in a small ectothermic species. The studied population inhabited a wall surrounding a city-park in Cesano Maderno (45.62°N, 9.15°E). On June, 2013 we recorded the positions of 53 adult lizards in a 50 cm ˟ 50 cm grid virtually superimposed to the wall. By using a thermal camera, we took a picture to characterize the thermal properties of each cell (mean and standard deviation of the temperature; proportion of pixel with temperature higher than the mean plus one standard deviation). We built the maximum entropy models of the thermal niche of each morph and then compared them using the fuzzy-k statistic. Mean temperature was excluded since it was spatially correlated with the vertical position of the cells. Each model was tested against the null hypothesis of no relationship with thermal variables, and performed better than chance. All the comparisons gave low k values, suggesting the three morphs having different thermal niches. R and Y showed a stronger relationship with the thermal variables than W and also a different kind of response to them, being R more affected by temperature standard deviation, Y also by the percentage of hot pixels, and W an intermediate case. These results supported, for the first time, the hypothesis of the occurrence of ecological differences between the three morphs of P. muralis
Un nuovo tipo di trappola per tritone punteggiato (Lissotriton vulgaris) e tritone crestato (Triturus carnifex)
No full textDurante il periodo riproduttivo, gli anfibi si spostano verso i bacini in cui avverranno gli accoppiamenti. Nella maggior parte degli studi focalizzati sui tritoni è necessario catturare un numero variabile di individui, al fine di stimare la consistenza numerica della popolazione riproduttiva, la fenologia oppure raccogliere campioni biologici e dati biometrici. In tutti questi studi la cattura deve essere contemporaneamente efficiente e il meno invasiva possibile, compatibilmente con il tipo di sito riproduttivo. Metodi di campionamento largamente utilizzati prevedono l'uso di retini, bottiglie tagliate a formare piccole nasse, reti da pesca e nasse per gamberi.
Nell'ambito di un progetto volto alla valutazione demografica di una popolazione di tritone punteggiato e tritone crestato in uno stagno nel Parco Regionale delle Groane, abbiamo ideato e costruito una trappola appositamente concepita per il sito studiato. Si tratta di una nassa cilindrica con aperture a imbuto disposte a spirale lungo l'asse principale. La struttura è realizzata in rete da giardino cucita con fil di ferro. Il diametro delle maglie della rete è di circa 3 mm. La nassa può essere posizionata sia in verticale, sia in orizzontale, mantenendo sempre una porzione galleggiante, grazie al polistirolo inserito all'interno. Durante due mesi di campionamento sono stati catturati oltre quattrocento tritoni, molti dei quali ricatturati più volte. Nonostante l'alta naturalità del sito, nella trappola, oltre ai tritoni, sono state catturate solo alcune rane verdi, qualche girino di rana rossa e alcuni ditischi.
La nassa da noi ideata si presenta quindi come uno strumento economico, leggero, di facile costruzione, efficiente nel campionamento dei tritoni e, al contempo, selettivo nei confronti delle altre specie palustri. Inoltre, essendo uno strumento non invasivo, può essere usata anche in ambienti ad elevata naturalità, laddove la protezione dell'ecosistema palustre è di primaria importanza
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
Genetic and phenotypic component in head shape of common wall lizard Podarcis muralis
No full textHead shape in lizards correlates with a wide range of environmental pressures, supporting the hypothesis that
patterns of phenotypic change represent adaptive responses to selective processes. However, natural selection promotes
evolutionary adaptation only if the trait under selection has enough heritable variation. In this study we used geometric
morphometrics and quantitative genetics to assess the heritability patterns of the head shape and size of common wall lizards
(Podarcis muralis). Genetic and phenotypic components were estimated using animal models, which showed that more
than half of the variation in head morphology is inheritable. Furthermore, at least five independent patterns of genetically
determined phenotypic change were detected. These outcomes confirm that morphological differentiation in common wall
lizards may reliably be regarded as the result of adaptive processes driven by natural selection
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
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