Daphnia metacommunity dynamics : the roles of inbreeding, parasitism, competition, and dispersal

The habitats of many species are not continuous but fragmented, either naturally or increasingly due to human land use. Communities of species inhabiting fragmented habitat patches are connected by dispersal and form a metacommunity, a spatial overlay of the metapopulations of the individual species. The factors enabling coexistence of different species in communities may shed light on the core questions of ecology, which is on the search for explanations for the abundance of species and their interactions with the biotic and abiotic environment. With this thesis, I aimed at contributing to a better understanding of the interplay of potential determinants of species coexistence at the local and regional scales in metacommunities. I studied a metacommunity of the three generalist filter-feeding planktonic water flea species Daphnia longispina, D. magna, and D. pulex, which form local communities in ephemeral freshwater rock pools although they have largely overlapping niches. To corroborate my observational and experimental findings, I combined them with a long-term demographic data set by V.I. Pajunen on the presence of the three species in over 500 rock pools since 1982. The largest and most abundant species D. magna is known to harbour a high diversity of ecto- and endoparasites, and the diversity of parasites in local D. magna populations was shown to correlate primarily with population age. I screened rock pool populations of the congeneric species D. longispina over a period of three years and inspected which epidemiological, spatial, temporal, and physicochemical factors explained most of the variance in the number of parasites. Contrary to the situation in D. magna, parasite richness in D. longispina was generally substantially lower, and surprisingly, the best predictor was the presence of D. magna, indicating that the co-occurring congeneric species might serve as a reservoir of parasites from which D. longispina is constantly inflicted. At the same time, the presence of parasites could be the decisive factor mediating coexistence between the two Daphnia species. Daphnia magna does not only carry the largest parasite burden but is as well the most dynamic species in terms of extinction and colonisation events in the metacommunity. To understand the factors of invasion success of D. magna, I conducted a fully factorial outdoor mesocosm experiment where D. magna clones that were outbred, unparasitised or did not face competition by resident D. longispina had a higher invasion success. The three factors inbreeding, parasitism, and interspecific competition are suggested to affect colonisation dynamics in the metacommunity and to determine whether the sequential arrival of Daphnia species in rock pool habitats can result in local coexistence. Not only invasion success proved to be diminished by competition, the competitive hierarchy of species is generally considered an important determinant for coexistence. Therefore I studied the interspecific competitive abilities of the three Daphnia rock pool species in two further outdoor mesocosm experiments. The interspecific competitive abilities of forty D. magna clones competing against D. longispina and D. pulex correlated positively and were higher when the clones originated from genetically more diverse populations, which is suggested to be a consequence of reduced inbreeding depression. The competitive abilities of the three Daphnia species competing in pairs against one another followed almost invariably a transitive competition hierarchy, i.e. the largest species D. magna was competitively superior to the intermediately sized D. pulex which in turn was competitively superior to the smallest species D. longispina. Such transitive competitive hierarchies are supportive of the size efficiency hypothesis which states that larger species dominate smaller species in the absence of predation because of their higher feeding efficiency. Conversely, I propose that the rare but naturally possibly more prevalent intransitive competitive relationships are a key factor for the maintenance of clonal and species diversity in Daphnia rock pool communities. Since rock pools are highly stochastic habitats, a requirement of local coexistence is the sufficient provisioning of immigrants by means of dispersal. Daphnia depend on passive dispersal by resting stages, so-called ephippia. To obtain a direct estimate of the absolute dispersal effort, I trapped ephippia over three years in areas inhabited predominantly by D. longispina and D. magna. The majority of caught ephippia stemmed from D. magna, which supports earlier conclusions that D. magna ephippia are more often exposed to the supposedly dominant dispersal agent wind since the species prefers smaller, more desiccation-prone rock pools. In contrast, I speculate that D. longispina may be dispersed predominantly by means of insects which may be charged by this species' buoyant ephippia

Brunstatt-Didenheim, Mulhouse – Deuxième Zac des Collines, Vallée 3 (tranche 2, phase 2)

Le diagnostic réalisé entre le 20 et le 23 septembre 2016, dans la Zac du Parc des Collines, sur le ban des communes de Mulhouse et de Didenheim, à l’est de l’avenue de Bruxelles, a été motivé par la sensibilité archéologique du secteur d’implantation du projet d’aménagement d’un dépôt de La Poste diligenté par la société SPL CIVITIA. Il complète l’opération de diagnostic prescrit en 2009 sur l’ensemble de la deuxième Zac des Collines, sur des terrains jusqu’à présent non disponibles. Une str..

Munchhouse – Lotissement du Canal, rue du Canal

Une opération de diagnostic a été prescrite à Munchhouse en prévision de nouvelles constructions dans un lotissement, sur une surface de 34 229 m2. Localisé au sud-ouest du noyau villageois actuel, les sondages n’ont révélé aucun indice d’occupation intéressant l’archéologie ou l’histoire de la commune

3.6 Non-uniform distribution of treated sucrose solution via trophallaxis by honeybees affects homing success variability and mortality

Background: Food sharing in a group via trophallaxis might lead to a non-uniform distribution of pesticide spiked sucrose solution between caged honeybees. This can cause high variability in the homing success rate or mortality among group members and treatment replicates. In order to improve the oral food distribution of tested sucrose solution we compared two feeding schemes with two or ten bees per cage (20 μL/bee) and evaluated the impact on homing success rate and mortality. Results: First results showed that food intake with the two-bees feeding regime is faster. Therefore, a more accurate dosing distribution among bees can be expected. We measured a less variable homing success rate and retuning time among runs and the corresponding treatments. Furthermore, mortality rate of the groupfeeding scheme with ten bees per cage resulted in higher mortality values when compared to the two-bees feeding scheme. This might be an indication for a better and more uniform distribution of the treated sucrose solution among two caged bees.Conclusion: Improving the uniform distribution of test items by orally treatment administration in smaller groups with honeybees should be discussed and considered, as toxicity endpoints of single-dosed wild bees are compared with group-dosed honeybees. Furthermore, to minimize the trophallaxis dependency regarding food distribution in group dosed honeybees.Background: Food sharing in a group via trophallaxis might lead to a non-uniform distribution of pesticide spiked sucrose solution between caged honeybees. This can cause high variability in the homing success rate or mortality among group members and treatment replicates. In order to improve the oral food distribution of tested sucrose solution we compared two feeding schemes with two or ten bees per cage (20 μL/bee) and evaluated the impact on homing success rate and mortality. Results: First results showed that food intake with the two-bees feeding regime is faster. Therefore, a more accurate dosing distribution among bees can be expected. We measured a less variable homing success rate and retuning time among runs and the corresponding treatments. Furthermore, mortality rate of the groupfeeding scheme with ten bees per cage resulted in higher mortality values when compared to the two-bees feeding scheme. This might be an indication for a better and more uniform distribution of the treated sucrose solution among two caged bees.Conclusion: Improving the uniform distribution of test items by orally treatment administration in smaller groups with honeybees should be discussed and considered, as toxicity endpoints of single-dosed wild bees are compared with group-dosed honeybees. Furthermore, to minimize the trophallaxis dependency regarding food distribution in group dosed honeybees

Assessing the Predictive Nature of Teacher and Student Writing Self-Regulation Discrepancy

In this study, we examine the extent to which the discrepancy between teacher-reported and student-reported self-regulatory behaviours during writing were associated with students’ end-of-year writing grades after controlling for student writing ability and other demographic characteristics. Results of our study, conducted with a sample of 201 middle grades students enrolled in a large, comprehensive suburban school district in the Mid-Atlantic U.S., suggest a significant and positive relationship between teacher discrepancy and grades, after controlling for writing ability, student self-regulation, gender, race/ethnicity, and SES. This has clear implications for the classroom, as it suggests that even after accounting for student difference in terms of ability background, and demographics, the effort that teachers perceive their students making in the fall are still associated with students’ year-end performance in their class. This represents some of the first frontline evidence of the predictive relationship between self-regulation discrepancy and student achievement in writing

Assessing the Predictive Nature of Teacher and Student Writing Self-Regulation Discrepancy

In this study, we examine the extent to which the discrepancy between teacher-reported and student-reported self-regulatory behaviours during writing were associated with students’ end-of-year writing grades after controlling for student writing ability and other demographic characteristics. Results of our study, conducted with a sample of 201 middle grades students enrolled in a large, comprehensive suburban school district in the Mid-Atlantic U.S., suggest a significant and positive relationship between teacher discrepancy and grades, after controlling for writing ability, student self-regulation, gender, race/ethnicity, and SES. This has clear implications for the classroom, as it suggests that even after accounting for student difference in terms of ability background, and demographics, the effort that teachers perceive their students making in the fall are still associated with students’ year-end performance in their class. This represents some of the first frontline evidence of the predictive relationship between self-regulation discrepancy and student achievement in writing

Veritaa: A distributed public key infrastructure with signature store

Today, the integrity and authenticity of digital documents and data are often hard to verify. Existing public key infrastructures (PKIs) are capable of certifying digital identities but do not provide solutions to store signatures immutably, and the process of certification is often not transparent. We propose Veritaa, a distributed public key infrastructure with an integrated signature store (DPKISS). The central part of Veritaa is the Graph of Trust that manages identity claims and singed declarations between identity claims and document identifiers. An application-specific distributed ledger is used to store the transactions that form the Graph of Trust immutably. For the distributed certification of identity claims, a reputation system based on signed trust declarations and domain vetting is used. In this work, we have designed and implemented the proposed architecture of Veritaa, created a testbed, and performed several experiments. The experiments show the benefits and the high performance of Veritaa

Encourage Self Regulated Learning in the Classroom

Self-regulated learning (SLR) is recognized as an important predictor of student academic motivation and achievement. This process requires students to independently plan, monitor, and assess their learning. However, few students naturally do this well. This paper provides a review of the literature including: the definition of SRL; an explanation of the relationship between SRL and motivation in the classroom; specific SRL strategies for student use; approaches for encouraging student SRL; and a discussion of some of the challenges educators might encounter while teaching students to be self-regulated, life-long learners

Resilience through Foresight: Implications for the Public Sector

Foresight is a strategic tool, which a state may implement to set priorities in politics and investments, show potential gaps in knowledge and information, and importantly better understand uncertainties. Therefore, foresight is a suitable method to increase a state’s resilience in various fields. The present study aims at answering the following question: What are the decisive factors for the use of foresight in enhancing state resilience, and what are the effective strategies for its practical implementation? The question is answered by taking a multi-method approach, combining a multi-step literature review with an illustrative case analysis of the implementation of foresight for resilience. The results are twofold: Firstly, by creating a structured framework based on research, the present paper develops a better understanding of projects aiming to achieve increased resilience through the application of foresight. Secondly, the case study on the United Kingdom’s Resilience Framework demonstrates the practical applicability of the framework and shows how the UK approaches resilience by applying foresight. The paper thereby highlights the potential of well-structured foresight projects as a central tool for states to help create an understanding of and make crucial decisions on resilience despite uncertainty. Abstrakt Foresight ist ein strategisches Instrument, das ein Staat einsetzen kann, um Prioritäten in Politik und Investitionen zu setzen, potenzielle Wissens- und Informationslücken aufzuzeigen und vor allem Unsicherheiten besser zu verstehen. Daher ist Foresight eine geeignete Methode, um die Resilienz eines Staates in verschiedenen Bereichen zu erhöhen. Die vorliegende Studie zielt darauf ab, folgende Frage zu beantworten: Was sind die entscheidenden Faktoren für den Einsatz von Foresight zur Stärkung staatlicher Resilienz und was sind die wirksamen Strategien für deren praktische Umsetzung? Die Frage wird durch einen multimethodischen Ansatz beantwortet, der eine mehrstufige Literaturrecherche mit einer anschaulichen Fallanalyse der Implementierung von Foresight für Resilienz kombiniert. Die Ergebnisse sind zweierlei: Erstens wird durch die Schaffung eines strukturierten Rahmens, der auf Forschung basiert, ein besseres Verständnis für Projekte entwickelt, die darauf abzielen, durch die Anwendung von Foresight mehr Resilienz zu erreichen. Zweitens demonstriert die Fallstudie zum „United Kingdom Resilience Framework“ die praktische Anwendbarkeit des Rahmens und zeigt, wie das Vereinigte Königreich Resilienz durch Vorausschau angeht. Die Studie zeigt damit das Potenzial von gut strukturierten Foresight-Projekten als zentrales Instrument für Staaten auf, um trotz Unsicherheit ein Verständnis für Resilienz zu schaffen und wichtige Entscheidungen zu treffen. Abstraite Foresight est un outil stratégique, qu’un État peut mettre en œuvre pour fixer des priorités en matière de politique et d’investissements, montrer les lacunes potentielles dans les connaissances et l’information, et surtout mieux comprendre les incertitudes. Par conséquent, la prospective est une méthode appropriée pour accroître la résilience d’un État dans divers domaines. La présente étude vise à répondre à la question suivante : quels sont les facteurs décisifs pour l’utilisation de Foresight dans le renforcement de la résilience de l’État, et quelles sont les stratégies efficaces pour sa mise en œuvre pratique ? On répond à la question en adoptant une approche multiméthodes, combinant une revue de la littérature en plusieurs étapes avec une analyse de cas illustrative de la mise en œuvre de la prospective pour la résilience. Les résultats sont doubles : premièrement, en créant un cadre structuré basé sur la recherche, le présent document développe une meilleure compréhension des projets visant à accroître la résilience par l’application de Foresight. Deuxièmement, l’étude de cas sur « United Kingdom Resilience Framework » démontre l’applicabilité pratique du cadre et montre comment le Royaume-Uni aborde la résilience en appliquant Foresight. L’étude souligne ainsi le potentiel de projets de prospective bien structurés en tant qu’outil central permettant aux États de comprendre et de prendre des décisions cruciales en matière de résilience malgré l’incertitude. Schlagworte: Foresight; Resilienz; Public Foresight; Strategisches Foresight; Zukünfte des Staats; Public Management Mots-Clés: Foresight; Résilience; Foresight public; Foresight stratégique; Futures de l’État; Public Managemen