1,720,955 research outputs found
Genetic diversity of six arable plants in relation to their Red List status
No full textIn Central Germany and throughout Europe, arable plants count among some of the most endangered plant species. Over the last few decades, the number and size of populations have been in sharp decline due to modern land use techniques, including the application of fertilizers, herbicide use and seed cleaning procedures. As arable plant species are underrepresented in population genetic studies, it is unknown whether agricultural intensification has affected the extant populations, and whether genetic structure varies among species with differing vulnerability in respect of their Red List status. We sampled 53 populations from 6 arable plant species throughout Central Germany. Random amplified polymorphic DNA analyses (RAPD) were applied to calculate measures of genetic diversity at the population level and genetic differentiation. Genetic diversity was found to be lowest in Bupleurum rotundifolium and Anagallis foemina, and highest in Consolida regalis and Nigella arvensis. The highest levels of genetic differentiation were observed among populations of An. foemina and B. rotundifolium but within populations in all other species. I broken vertical bar(ST) values differed strongly ranging between 0.116 for C. regalis and 0.679 for An. foemina. Patterns of genetic structure were related to the Red List status for all the species studied except An. foemina, for which it should consequently be raised. Our data confirm that even relatively recent threats are accompanied by detrimental genetic structure. As losses of populations and increased fragmentation have occurred in all common and uncommon species, the situation for arable plants could change for the worse in the following decades, highlighting the need for consistent monitoring.Graduiertenforderung of Saxony-Anhal
Spatial genetic structure and low diversity of the rare arable plant Bupleurum rotundifolium L. indicate fragmentation in Central Europe
No full textMany threatened plant species have genetic structures indicating effects of fragmentation, and in Central Europe arable plants are among the most threatened taxa. Although this threat has developed only recently in the course of agricultural intensification, their annual life form makes arable plants relatively sensitive to increasing fragmentation and decreasing population sizes. One of Central Europe's rarest arable plant species is Bupleurum rotundifolium (Apiaceae). To analyze the genetic structure and diversity of this species we sampled 27 populations of B. rotundifolium in Central Europe, and assessed genetic structure by amplified fragment length polymorphism (AFLP) fingerprinting. Ordination, clustering and also Bayesian analysis suggested that most of the populations of the Eastern part of Germany formed one cluster, and most of the Western German populations as well as populations from outside Germany built another group. The two clusters accounted for 24% of differences in genetic structure of B. rotundifolium populations, while there was relatively strong differentiation among (41% variance) and within populations of a given group (35% variance). The overall phi(ST)-value was very high (0.65) and there was evidence for isolation-by-distance. Values of genetic diversity were very low for B. rotundifolium. The proportion of polymorphic loci per population varied between 9.4% and 38.7%, with those from eastern Germany being significantly less diverse (mean 19.1% vs. 25.5%). (C) 2012 Elsevier B.V. All rights reserved.Graduiertenforderung of Saxony-Anhal
Keeping your food fresh: active manipulation of cytokinin-metabolism by a cell content feeder
No full textCytokinins play a central role in plant physiology, including regulation of senescence and nutrient translocation. Recent studies have revived interest in their role in plant-insect interactions. At the end of the sixties, some scientists suggested for the first time that phytophagous insects might manipulate cytokinin levels in the tissues where they feed to increase their sink strength (Engelbrecht et al., Nature, 1969). Here, we present our results on the interactions between the cell-content feeding mirid Tupiocoris notatus and the wild tobacco Nicotiana attenuata. Using highly sensitive LC-MS techniques, we detected two types of active cytokinins present in mirid bodies: isopentenyl-adenine (IP), and isopentenyl-adenosine (IPR). Surprisingly, the free base IP was ten to fifty times as concentrated in mirid bodies as in the leaf tissues where T. notatus normally feeds. By using N15-labeled plants, we showed that T. notatus specifically transfers! these two types of cytokinins into the leaves on which it feeds. The effects of T. notatus damage on the physiology of tobacco leaves was assessed by determining the concentration of soluble sugars, soluble proteins, free amino acids, and photosynthetic parameters over a time course during mirid attack. Responses were compared in wild-type plants and in transgenic plants with manipulated levels of cytokinins or impaired cytokinin perception. Even when insects had damaged the majority of the leaf-surface, levels of nutrients remained close to levels in undamaged controls. In contrast, plants with altered cytokinin metabolism and signalling showed larger changes in nutrient levels during T. notatus feeding. Our results suggest that T. notatus compensates for the damage it causes by manipulating cytokinin signalling in damaged leaves
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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