1,721,002 research outputs found
Contrasting patterns of climatic niche divergence in Trebouxia—A alade of lichen-forming algae.
Full text linkLichen associations are overwhelmingly supported by carbon produced by photosynthetic algal symbionts. These algae have diversified to occupy nearly all climates and continents; however, we have a limited understanding of how their climatic niches have evolved through time. Here we extend previous work and ask whether phylogenetic signal in, and the evolution of, climatic niche, varies across climatic variables, phylogenetic scales, and among algal lineages in Trebouxia—the most common genus of lichen-forming algae. Our analyses reveal heterogeneous levels of
phylogenetic signal across variables, and that contrasting models of evolution underlie the evolution of climatic niche divergence. Together these analyses demonstrate the variable processes responsible for shaping climatic tolerance in Trebouxia, and provide a framework within which to better understand potential responses to climate change associated perturbations. Such predictions reveal a disturbing trend in which the pace at which modern climate change is proceeding will vastly exceed the rate at which Trebouxia climatic niches have previously evolved
Macroecological diversification and convergence in a clade of keystone symbionts.
Full text linkLichens are classic models of symbiosis, and one of the most frequent nutritional modes among fungi. The ecologically and
geographically widespread lichen-forming algal (LFA) genus Trebouxia is one of the best-studied groups of LFA and
associates with over 7000 fungal species. Despite its importance, little is known about its diversification. We synthesized
twenty years of publicly available data by characterizing the ecological preferences of this group and testing for
time-variant shifts in climatic regimes over a distribution of trees. We found evidence for limited shifts among regimes, but
that disparate lineages convergently evolved similar ecological tolerances. Early Trebouxia lineages were largely forest
specialists or habitat generalists that occupied a regime whose extant members occur in moderate climates. Trebouxia then
convergently diversified in non-forested habitats and expanded into regimes whose modern representatives occupy
wet-warm and cool-dry climates. We rejected models in which climatic diversification slowed through time, suggesting
climatic diversification is inconsistent with that expected under an adaptive radiation. In addition, we found that climatic
and vegetative regime shifts broadly coincided with the evolution of biomes and associated or similar taxa. Together, our
work illustrates how this keystone symbiont from an iconic symbiosis evolved to occupy diverse habitats across the globe
Should we hail the Red King: evolutionary consequences of a mutualistic lifestyle in genomes of lichenized fungi
Full text linkThe Red Queen dynamic is often brought into play for antagonistic relationships. However, the coevolutionary effects of mutualistic interactions, which predict slower evolution for interacting organisms (Red King), have been investigated to a lesser extent. Lichens are a stable, mutualistic relationship of fungi and cyanobacteria and/ or algae, which originated several times independently during the evolution of fungi. Therefore, they represent a suitable system to investigate the coevolutionary effect of mutualism on the fungal genome. We measured substitution rates and selective pressure of about 2000 protein-coding genes (plus the rDNA region) in two different classes of Ascomycota, each consisting of closely related lineages of lichenized and non-lichenized fungi. Our results show that independent lichenized clades are characterized by significantly slower rates for both synonymous and non-synonymous substitutions. We hypothesize that this evolutionary pattern is connected to the lichen life cycle (longer generation time of lichenized fungi) rather than a result of different selection strengths, which is described as the main driver for the Red Kind dynamic. This first empirical evidence of slower evolution in lichens provides an important insight on how biotic cooperative interactions are able to shape the evolution of symbiotic organisms
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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