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Die Oekologie, Genetik und Evolution zweier Saxifraga Arten mit unterschiedlicher Fragmentierungsgeschichte
No full textThe aim of this thesis was to study the ecology, genetics and evolution of two congeneric species with different fragmentation histories. Saxifraga sponhemica is a glacial relict species of long-term fragmented lowland rock and scree habitats, and has been naturally rare for thousands of years with a disjunct distribution in Central Europe. Saxifraga granulata is a formerly common species of species-rich semi-natural grasslands that has become recently fragmented due to the intensification of agricultural practices. Fragmentation generally leads to loss of genetic diversity due to drift and inbreeding, reduced mean fitness and increased extinction rates of populations. Formerly common species are expected to be particularly susceptible to the recent anthropogenic fragmentation of their habitats.
An analysis of the genetic diversity and the genetic structure of S. sponhemica populations based on RAPD-markers showed that in most populations considerable genetic variability has been preserved. An isolation by distance pattern of genetic differentiation suggested historical gene flow during the last glaciation when suitable habitats were much more abundant. Long-lived plant species can thus maintain historic genetic patterns despite the small size and strong isolation of populations.
We grew plants form several families per population in a common garden to study the quantitative genetic variation within and among populations. We found several lines of evidence for divergent selection. Most population trait means were significantly related to climate gradients, indicating adaptation. Quantitative genetic differentiation increased with climatic distance and with geographical distance, even when neutral molecular divergence was controlled for, and quantitative genetic differentiation (QST) exceeded molecular genetic differentiation (FST) for some traits. Traits under strong selection showed little genetic variation within populations. The evolutionary potential of a population was not related to its size, the performance of the population or its neutral genetic diversity. However, performance in the common garden was lower for plants from populations with reduced molecular genetic variation, suggesting inbreeding depression due to genetic erosion. Studies of molecular and quantitative genetic variation may thus provide complementary insights important for the conservation of rare species. S. sponhemica does not appear to be genetically threatened in the short term, but populations are threatened by habitat destruction. A conservation measure could be to create new populations in suitable habitats with seeds from the same region to avoid local maladaptation.
We also studied the RAPD molecular and the quantitative genetic structure of 19 populations of the declining grassland plant S. granulata in a geographically restricted area in Luxembourg and Germany. Differentiation for quantitative traits (QST) was slightly lower than differentiation for molecular markers (FST) suggesting homogenising selection for optimal trait values. Contrary to our expectations, the level of differentiation among fragmented S. granulata populations was low, and molecular genetic diversity was high and was not correlated with the size or the mean plant performance of populations. Gene flow by long distance dispersal or the longevity, clonality and polyploidy of S.granulata may have prevented genetic erosion due to drift. To avoid genetic erosion in the future, extant populations should be preserved and gene flow among populations should be maintained.
Habitat fragmentation has led to increased inbreeding and inbreeding depression in many species. We investigated the effects of increased inbreeding and of intra- and interpopulation crosses on the reproduction and performance of S. granulata. Between population crosses may result in increased performance (heterosis), but may also lead to the disruption of coadapted gene complexes and to decreased performance (outbreeding depression). Inbreeding depression affected all traits in the F1 generation, but was stronger for traits expressed late during development and varied among families. Multiplicative fitness of the F2 generation after serial inbreeding was extremely low, but there was heterosis after crossing inbred lines. Outbreeding depression was however not observed in the F2. We also subjected the first generation of offspring to a fertilization and stress treatments (competition and defoliation). The adaptive plasticity of offspring from selfing and from interpopulation crosses in response to nutrient addition was reduced. Outbreeding depression was also observed in response to stress. The results suggest that continuous inbreeding may drastically reduce the fitness of plants, but effects may be environment-dependent.
Overall, the results of this thesis advance knowledge on the role of time since habitat fragmentation, of historic connectivity among populations, and of life history traits such as longevity and clonality on the processes of selection and drift that shape the genetic variation within and among populations. It stresses the importance of using both molecular and quantitative genetic tools to gain complementary insight for the conservation of rare and endangered plant species. It shows how knowledge about the vulnerability to increased inbreeding and the potential risks of artificially increasing gene flow between populations of recently fragmented species contributes to their effective conservation.Das Ziel dieser Arbeit war es, ökologische, genetische und evolutionäre Aspekte zweier Arten derselben Gattung mit unterschiedlicher Fragmentierungsgeschichte zu untersuchen.
Saxifraga sponhemica ist eine Art mit einer disjunkten Verbreitung in Zentraleuropa, die als Eiszeitrelikt auf isolierten Felswänden und Schutthalden wächst. Saxifraga granulata hingegen ist eine früher häufige Art artenreicher, halb-natürlicher, mesophiler Mähwiesen, die seit den Ende der 50er-Jahre durch die chemische Düngung und die Umwandlung von traditionellem Grasland in Silowiesen verändert und fragmentiert wurden. Negative Effekte der Fragmentierung für Populationen sind verringerte genetische Diversität durch Drift und Inzucht, eine verringerte Fitness der Pflanzen aufgrund von Inzuchtdepression und in der Folge ein erhöhtes Aussterberisko der Populationen. Es gibt jedoch nur wenige Studien, die den Effekt der Fragmentierung auf einst häufige Arten und natürlich seltene Arten derselben Gattung vergleichend untersucht haben.
Eine Studie der genetischen Diversität und der genetischen Struktur von S. sponhemica Populationen mit Hilfe von molekularen RAPD-Markern zeigte, dass dank der Langlebigkeit der Art die Populationen eine hohe genetische Diversität bewahrt haben. Die genetische Differenzierung der Populationen nahm mit ihrer Entfernung voneinander zu, was auf historischen Genfluss während der letzten Eiszeit hindeutet, als es vermutlich viel mehr Vorkommen der Art gab. Unsere Ergebnisse deuten darauf hin, dass langlebige Pflanzen historische genetische Muster trotz ihrer heute kleinen und z.T. extrem isolierten Populationen über lange Zeiträume bewahren können.
Um die quantitativ-genetische Variation von Merkmalen innerhalb und zwischen Populationen von S. sponhemica zu erfassen, wurden Samen verschiedener Individuen in den Populationen gesammelt und Keimlinge unter gleichen Bedingungen angezogen. Wir fanden verschiedene Hinweise auf divergente Selektion in den Populationen. Die meisten Merkmale zeigten klinale Variation in Beziehung zu Klimagradienten. Die genetische Differenzierung zwischen Populationen nahm mit den klimatischen Unterschieden und geographischen Distanzen zwischen Populationen zu, auch wenn für die molekular-genetische Differenzierung kontrolliert wurde. Außerdem war die quantitativ-genetische Variation einiger Merkmale zwischen den Populationen deutlich höher als die der molekular-genetischen Marker. Merkmale die sich stark zwischen Populationen unterschieden, zeigten weniger Variation innerhalb von Populationen. Es gab keine Beziehung zwischen dem evolutionären Potential einer Population, und ihrer Populationsgrösse, ihrer Fitness, oder ihrer neutral-genetischen Diversität. Die Fitness von Pflanzen aus Populationen mit geringer molekular-genetischer Diversität war reduziert, was ein Hinweis auf Inzuchtdepression ist. Unsere Ergebnisse weisen darauf hin, dass molekular- und quantitativ-genetische Studien komplementäre Erkenntnisse liefern können, die beide für die Erhaltung von Arten wichtig sind. Die Populationen von S. sponhemica sind gegenwärtig eher durch Habitatzerstörung gefährdet als durch genetische Probleme. Eine Naturschutzmaßnahme könnte darin bestehen, neue Populationen in geeigneten Habitaten anzusiedeln mit Samen aus der gleichen Region, um Fehlanpassungen zu vermeiden.
Wir untersuchten die molekular-und quantitativ genetische Variation innerhalb und zwischen 19 Populationen von Saxifraga granulata in einem geografisch eng begrenzten Gebiet in Luxemburg und Deutschland. Die genetischen Unterschiede zwischen den Populationen in quantitativen Merkmalen waren z.T. geringer als diejenigen in neutralen Markern, was auf stabilisierende Selektion hindeutet. Entgegen unseren Erwartungen war die Differenzierung zwischen den fragmentierten Populationen gering. Außerdem war die genetische Diversität innerhalb von Population hoch und war nicht mit der Populationsgröße oder der mittleren Pflanzengröße korreliert. Gründe dafür könnten eine Ausbreitung der Samen über längere Distanzen durch den Wind oder durch Mähmaschinen, sowie die Langlebigkeit, Klonalität und Polyploidie von S. granulata sein, die einen Verlust der genetischen Diversität durch Drift und die genetische Differenzierung zwischen Populationen verhindert haben. Es ist trotzdem wichtig, die bestehenden Populationen zu schützen, und den Genfluss zwischen Populationen zu erhalten um einen Verlust an genetischer Diversität zu vermeiden.
Die Fragmentierung der Habitate hat zu erhöhter Inzucht und Inzuchtdepression in den Populationen vieler Arten geführt.
Wir untersuchten den Einfluss von Inzucht und Auszucht innerhalb und zwischen Populationen auf die Reproduktion und die Vitalität zweier Generationen von Nachkommen von S. granulata. Kreuzungen zwischen Populationen könnten einerseits den Grad der Heterozygotie und die Fitness der Nachkommen steigern, andererseits aber auch die Fitness von Pflanzen durch das Aufbrechen koadaptierter Genkomplexe verringern. Inzuchtdepression beeinflusste alle Merkmale in der F1 Generation; dabei variierte der Einfluss zwischen Familien und die Inzucht wirkte sich stärker auf Merkmale aus, die sich spät im Lebenszyklus der Pflanze ausprägen. Die multiplikative Fitness der nochmals ingezüchteten F2 Generation war extrem gering. Kreuzungen ingezüchteter Linien zeigten keine Auszuchtdepression, sondern Heterosis. Pflanzen der F1 Generation wurden einer Düngung und zwei Stressbehandlungen(Konkurrenz und Entblätterung) unterzogen. Ingezüchtete Pflanzen wiesen eine geringere adaptive Plastizität als Reaktion auf Düngung auf und zeigten Auszuchtdepression als Reaktion auf die Stressbehandlungen. Unsere Ergebnisse deuten darauf hin, dass fortgesetzte Inzucht die Fitness der Pflanzen drastisch reduziert, aber dass die Effekte umweltabhängig sind.
Insgesamt erweitern unsere Untersuchungen das Wissen über den Einfluss der Dauer der Fragmentierung, der historischen Konnektivität der Populationen und von Eigenschaften wie Langlebigkeit oder Klonalität auf die evolutionären Prozesse von Selektion und genetischer Drift, welche die genetische Variation innerhalb und zwischen Populationen bestimmen. Die Studien zeigen dass molekulare und quantitativ genetische Untersuchungen
ergänzende Informationen für den Schutz von seltenen und gefährdeten Pflanzen liefern. Darüber hinaus zeigen sie die Bedeutung von Studien zur Empfindlichkeit von Populationen gegenüber Inzucht und zum Potential und den Risiken einer künstlichen Erhöhung des Genflusses zwischen den Populationen kürzlich fragmentierter Arten für einen effektiven Artenschutz
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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