1,721,084 research outputs found
Phylogenetic relationships among extremotolerant rock-inhabiting fungi and their associations with algae
Full text linkFungi with dark-coloured mycelia - also known as black fungi - form a ubiquitous fraction of microbial communities on rock surfaces all over the world. These organisms show a high capacity to adapt to a wide range of ecological conditions, including those peculiar of extreme environments. Their high tolerance to multiple abiotic stresses, such as solar radiation and osmotic stress is assured by the production of melanin pigments and osmoprotective compounds. The cosmopolitan genera Lichenothelia and Saxomyces were taken as iconic representatives of polyextremotolerant rock-inhabiting black fungi. I investigated their phylogenetic relationships with an extended taxon sampling within the class Dothideomycetes, the most diverse and life-style rich fungal class in Ascomycota. The three loci phylogenetic inference I set up, considering both environmental samples and culture isolates, highlighted the paraphyly of the two genera. The integrative taxonomy approach based on morphological as well as phylogenetic evidences allowed the taxonomical revision of the genera and the description of three new taxa.
Rock inhabiting fungi often share substrata with green algae and cyanobacteria and some of them are associated with lichen thalli. Lichenothelia is of a particular interest because it includes lichen parasites and species which are loosely associated with algae or which grow independently on rock. Given their life style plasticity, we chose it for an in vitro culture experiment, studying the development of three Lichenothelia species when co-cultured with two different subaerial algae isolated from lichens (i.e., lichen photobionts). The results showed that the presence of algae neither influence the growth rate of fungi nor the formation of any lichen-like structure. However, this standardized approach proved suitable for future investigations on fungal-algal interactions in other systems.
Previous multi-locus phylogenies of Dothideomycetes have investigated evolutionary relationships at order and family level within the class but they often failed to resolve the early diverging nodes, which were generating inconsistent placements of some clades. Here, I applied a phylogenomic approach to resolve relationships in Dothideomycetes, adding the newly sequenced Lichenothelia and Saxomyces genomes, to a wide dataset comprised of 238 individuals. I explored the influence of tree inference methods, supermatrix vs. coalescent-based species tree, and the impact of varying amounts of genomic data. The phylogenomic reconstructions, based on up to three thousand genes, provide well-supported topologies for Dothideomycetes, recovering Lichenothelia and Saxomyces among the earliest diverging lineages in the class together with other rock inhabiting fungi and lichens and thus, suggesting the rock-inhabiting life style as ancestral in the class.
Further studies will be necessary to shed light on the molecular bases of stress tolerance and latent capacity of establishing symbiosis of these fungi
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
Querying moving events in wireless sensor networks
No full textThe detection and tracking of composite events in Wireless Sensor Networks often employ ad-hoc solutions that aim at detecting and tracking only specific types of events or use generic query languages that are not specifically built to manage events. We propose a new query language and an in-network query processing solution that enable the definition of queries to track and gather information from events, using wireless sensor networks. The proposed language provides clauses aimed at defining dynamic tracking tasks and the autonomous migration of the queries on the network, depending on the event mobility. We describe the query model and the language, discuss its implementation, and present the results of the comparison with a TinyDB-like approach. We show that our approach is scalable with event mobility and that it is more energy efficient than TinyDB-like approache
Extremotolerant black fungi from rocks and lichens.
No full textIn contrast to the majority of fungi, which live more or less comfortably inside of hosts or substrates, some lineages have specialised to thrive on exposed surfaces. With little competition on nutrient-deprived conditions, such a stressful lifestyle also requires adaptations to fluctuations of hydration, among other challenges. Fungi in these situations also need to shield their cell content from excessive radiation using various kinds of pigments in their cell walls. The symbiotic thalli of lichen-forming fungi are one example on how to cope with conditions of exposed surfaces. Lichenforming fungi develop diverse forms of characteristically compacted mycelial morphologies to filter light to sheltered photosynthetic algae. Another large group of fungi does not depend on symbiotic partners, but it is characterised by dark pigments, and unlike lichens, these fungi may tolerate much higher levels of air pollution. These
‘black’ fungi, as they are commonly called, are the focus of this chapter. We provide an overview of the current understanding of diversity and taxonomy of black fungi and review their phenotypic traits. As we previously recognised ecological and evolutionary links of black fungi with the lichen symbiosis, we also discuss first results from co-culture experiments of black fungi with algae. Finally, we also review first insights gained from -omics approaches. The phenotypes of black fungi have evolved in different lineages of ascomycetes. Under the extremes of abiotic conditions, the typical morphology is usually restricted to vegetative mycelia with insufficient diagnostic characters for species recognition. Hence it is practically impossible to identify the species directly in the environment or with a stereomicroscope. Diagnostic phenotypic characters are often expressed under controlled laboratory conditions, even though species commonly lack sexual structures. Analyses of DNA sequence data are the only way to prove the relationship of species with similar morphology and to place these fungi in a phylogenetic framework. Molecular approaches showed both that many lineages exist which have not been named so far while described taxa turned out to be polyphyletic (e.g. Ertz et al. 2014). DNA data are still of limited use to recognise species as little is known about the genetic variation within species, but they clearly showed that black fungi are phylogenetically more diverse than previously thought and that they primarily belong to two lineages of ascomycetes, the early diverging clades of Dothideomycetes and Eurotiomycetes in Ascomycota
Query Processing in a Mediator System for Data and Multimedia
No full textManaging data and multimedia sources with a unique tool is a chal- lenging issue. In this paper, the capabilities of the MOMIS integration system and the MILOS multimedia content management system are coupled, thus providing a methodology and a tool for building and querying an integrated virtual view of data and multimedia sources
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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