Abstract :The main goal of this stud y was to quantify the effect s of landscape structure on the abundance of Ruby-throate d Hummingbird s (Archilochus colubris) in forest patches and this, while accounting for its indirect effects on open flower community an d the occurrence of Yellow-bellied Sapsucker s (Sphympicus varius), a potential commensal of hummingbirds. We sampled 40 forest patches (0. 5 to >10 0 ha ) where we had installed 2 nectar feeders (forest edge and 40 m within forest ) during 2 breeding season s (2006 and 2007) . We visited forest patches weekly and recorded the number of hummingbirds detected within 10 m of feeders during 10 min. Mean daily artificial nectar consumption by hummingbirds, as well as their relative total abundance an d the respective relative abundance of adult males and females, were all affected by forest cover. Except for the relative total abundance, this effect of forest cover depended upon the size of forest patches. Nectar consumption and abundance generally peaked in forest patches of intermediate size found in landscapes characterized by intermediate forest cover. Mea n daily artificial nectar consumption and the relative total abundance, a s well as that of males, were higher at feeders located on the forest edge compared to 40 m inside forest patches. Regarding indirect landscape effects, landscape structure influenced the structure of open flower communities surrounding feeders, which in turn, affected the relative total abundance of hummingbirds, a s well as that of adult males. On the other hand, we failed to find strong evidence that landscape structure affected the occurrence of Yellow-bellied Sapsuckers or that the latter influenced Ruby-throated Hummingbird abundance patterns. These results support the idea that landscape structure may affect the abundance pattern of a species directly as well as through mechanisms which are themselves dependent upon the composition and configuration of landscapes //Résumé : La structure des paysages peut influencer l'écologie d'une espèce directement, en contraignant ses mouvements, par exemple, de même qu'indirectement en affectant, entre autres, l'abondance de ses proies ou prédateurs. Quoique plusieurs études aient tenté de quantifier l'influence de la structure du paysage sur les patrons d'abondance, rares sont celles qui ont mesuré simultanément les effets directs et indirects du paysage. L'objectif de ce mémoire consiste à modéliser simultanément les effets directs de la structure du paysage sur l'abondance relative du Colibri à gorge rubis ( Archilochus colubris ) et sa consommation de nectar artificiel ainsi que les effets indirects par lesquels le paysage peut aussi agir tels la disponibilité en ressources alimentaires (communautés floristiques) et la relation interspécifique de commensalisme avec le Pic maculé ( Sphyrapicus varius ). Pour ce faire, j'ai échantillonné 40 îlots forestiers (0,5 à >100 ha) dans la région de l'Estrie (Québec, Canada). À chacun d'eux, j'ai installé deux abreuvoirs (en bordure et 40 m à l'intérieur) durant les étés 2006 et 2007 et ont été visités de façon hebdomadaire. J'ai détecté une relation quadratique du couvert forestier dans le paysage avec l'abondance totale relative, celle des mâles et des femelles ainsi que pour la consommation quotidienne moyenne. Ces effets varient en fonction de la taille d'îlot sauf pour l'abondance relative totale. Les valeurs maximales se situent à des niveaux intermédiaires de couvert forestier et de taille d'îlots. Certaines caractéristiques mesurées étaient à l'échelle locale comme la position de l'abreuvoir dans l'îlot forestier ou la structure de la végétation. J'ai détecté un effet de bordure pour toutes les variables sauf l'abondance des femelles. L'indice de structure de végétation n'avait d'influence que sur l'abondance des mâles. Concernant les effets indirects, l'ensemble des variables du paysage explique 69,61% de l'indice de communauté floristique et ce dernier a un effet significatif sur l'abondance totale et l'abondance des colibris mâles. Pour la relation avec le pic, les variables du paysage mesurées n'ont pas permis de détecter un effet. De plus, bien qu'étant une variable non significative, les modèles incluant la présence du Pic maculé étaient généralement parmi les plus performants. L'ensemble de ces résultats soutient l'importance de combiner l'écologie du paysage et l'écologie comportementale dans les mêmes modèles afin de tenir compte non seulement des effets directs mais aussi des effets indirects du paysage //

Approximately 43% of college students report experiencing suicidal ideation in the past year, and suicide is the 2nd leading cause of death among college students, making it a significant public health concern. Development of successful suicide intervention and prevention strategies is predicated on identification of risk (e.g. negative life events, hopelessness) and protective factors (e.g. self-compassion) that may be targeted for treatment. A well-established linkage exists between life stressors and suicidal behavior; however, potential mechanisms of action underlying this association are under-researched. It may be that negative life events contribute to feelings of hopelessness, which is conceptualized as negative beliefs and expectations about one’s self and future. However, not all persons who experience negative life events and hopelessness become suicidal, perhaps due to protective factors such as self-compassion. Comprised of self-kindness, mindfulness and sense of common humanity, self-compassion may contribute to emotional resilience when negative life events occur; however, this premise has not been previously examined. We hypothesized that hopelessness would mediate the relation between negative life events and suicidal behaviors, such that negative life events would be related to increased feelings of hopelessness and, in turn, to greater risk for suicidal behavior. We also hypothesized that self-compassion would beneficially moderate the mediating effect of hopelessness. Our sample of college students (n=338) were primarily female (67%; n=227) and White (89.6%; n=294), with a mean age of 21.8 years (SD=4.7). Participants completed self-report measures including the Life Events Scale, the Beck Hopelessness Inventory, the Suicide Behaviors Questionnaire - Revised, and the Self-Compassion Scale. Supporting our hypotheses, hopelessness fully mediated the relation between negative life events and suicidal behavior (DE=.07, SE=.06, 95% CI=.05,.28,p

Non-suicidal self-injury (NSSI), or deliberate self-harm, and suicidal behaviors are significant public health concerns, and college students may be at particular risk. For instance, approximately 17% of college students engage in NSSI and suicide is the 2nd leading cause of death in college students. Commonalities between NSSI and suicidal behavior exist, including etiology; as an example, misuse of substances and interpersonal difficulties are related to both outcomes. For college students, substance use disorders and social dysfunction are two of the most common psychosocial problems; for instance, 22% of students report illicit drug use and social isolation, loneliness and separation from traditional support systems are common collegiate stressors. According to the Interpersonal Theory of Suicide, two pertinent interpersonal risk factors are perceived burdensomeness (the belief that one is a liability to others) and thwarted belongingness (the unmet need to belong among others). When present, substance misuse and interpersonal dysfunction may facilitate the transition between NSSI and suicidal behavior; however, this premise has not been previously examined. As such, we hypothesized that substance abuse would mediate the relation between NSSI and suicidal behavior, such that engagement in NSSI would be related to greater use of substances and, in turn, to suicidal behavior. Further, we hypothesized that thwarted interpersonal needs would moderate this mediating effect, such that increased TB and PB would exacerbate the mediating effect of substance misuse. Our sample of college students (N=338) was primarily white (89.6%; n=294), female (67%; n=225), and had an average age of 21.8 years (SD=4.7). Participants completed the Suicide Behaviors Questionnaire-Revised, the Self-Harm Inventory, the Interpersonal Needs Questionnaire, and the Drug Abuse Screening Test. Supporting hypotheses, substance abuse partially mediated the relationship between NSSI and suicidal behavior (DE=1.30, SE=.10, p

A análise dos efeitos indiretos externos dos precedentes do STF e STJ (1996 a 2011) acerca da Lei de Diretrizes e Bases de 1996 (LDB-1996) parte do conteúdo e natureza do direito à educação que definem a posição jurídica dessa lei nacional materialmente constitucional, que tem promovido mutação universalizante-focalizante do direito à educação previsto na Constituição. Resultantes do caráter abstrativizado do precedente judicial das cortes superiores, os efeitos indiretos externos (indirect effect external) configuram o impacto político das decisões judiciais, no momento pós-decisões judiciais (the aftermath of judicial decisions), verificando-se nos casos em que o governo generaliza uma decisão da corte, mediante a alteração da política pública e, para alguns autores, têm a potencialidade de beneficiar aqueles que não têm recursos para litigar (GAURI; BRINKS). No ciclo de judicialização das políticas públicas (the life-cycle of public-policy litigation), a eficácia expansiva do precedente implica comandos que influenciam a ampliação do direito social àqueles potenciais demandantes. No contexto de ativismo judicial e buraco negro legislativo, a questão se o Judiciário prejudica ou contribui para a política democrática é analisada segundo os conceitos de accountability e responsividade diante dos impactos políticos dos precedentes judiciais a exigir o diálogo interinstitucional entre os poderes. Empiricamente, analisam-se os casos paradigmáticos das cotas raciais do STF de 2012 e os efeitos indiretos externos dessas decisões configurados na resposta política dada pela aprovação da Lei nº 12.711/12 e do Decreto nº 7.824/12. Metodologicamente, após o mapeamento temático dos acórdãos do STJ e do STF de 1996 a 2011 acerca da LDB-1996 (obtidos através da pesquisa com o critério legislativo nos sites www.stf.jus.br e www.stj.jus.br), afere-se a potencialidade desses efeitos políticos nos casos paradigmáticos do STF e STJ a evidencisar como/se promove: restrição/ampliação de políticas públicas; (des)consideração dos recursos financeiros; efeito multiplicador; e/ou acesso ou qualidade do ensino. / The analysis of indirect effect external of Supreme Federal Court STFs and Superior Court of Justice STJs cases in the period of 1996-2011 about the 1996 National Education Law (LDB-1996) begins with the right to education content and nature that define the substantial constitutional position, which has promoted informal interpretation changes based on the focalization and universalization of the constitutional right to education. Resulting from the abstract character of higher courts rulings and considering, the aftermath of judicial decisions, specifically its indirect effect external, shapes its political impact that and take place \"where government generalizes a decision of the court, by changing public policy\" and, for some authors, with the potential to benefit those who can not afford to litigate (GAURI; BRINKS). In the life-cycle of public-policy litigation the expansive compliance implies commands that influence the expansion of social rights to those potential plaintiffs. In the context of judicial activism\" and Congress \"black hole\", the question whether the judiciary contributes to democratic policy is analyzed with the accountability and responsiveness of those rulings that demand institutional dialogue between powers. Empirically, the 2012 STF racial quotas cases illustrate the indirect effect external by the approval of the Law No. 12,711 and Decree No. 7,824 of 2012. Methodologically, after the thematic mapping of STF and STJ rulings from 1996 to 2011 about the LDB-1996 (legislative research criteria on www.stf.jus.br and www.stj.jus.br websites) it is assessed its potential political effects with the following questions: the ruling promotes a restriction/extension of public policies?; does/not considers of financial resources?; has demonstratate \"multiplier effect\"; or/and decides about education access/quality.

Die Eutrophierung von Fließgewässern führt besonders im Frühjahr zur Zunahme der Biomasse des benthischen Aufwuchses. Dies kann zur reduzierter Infiltration von Wasser in die Gewässersohle führen und wichtige Funktionen von Fließgewässerökosystems stören. Verschiedene Studien konnten zeigen, dass invertebrate Weidegänger (Grazer) in der Lage sind die Biomasse des Aufwuchses in Fließgewässern effektiv zu reduzieren. Diese wichtige ökologische Funktion, das benthische Grazing, kann dazu beitragen negative Effekte der Eutrophierung in Fließgewässern zu kompensieren. Relevante invertebrate Grazer sind unter anderem die Larven der Eintagsfliege Rhithrogena semicolorata, die hohe Biomassen in Fließgewässern erreichen und eine hohe Spezialisierung auf Aufwuchs zeigen. Die Larven von R. semicolorata sind während ihres einjährigen Lebenszykluses Pestiziden ausgesetzt, welche ihre Entwicklung beeinträchtigen können. Um die Effekte von Pestiziden auf die Entwicklung dieser wichtigen Grazer zu untersuchen wurden drei Expositionsszenarien in Anlehnung an reale Bedingungen im Freiland untersucht. Das erste Szenario untersucht die Effekten einer Exposition mit dem Herbizid Terbutryn auf die Grazer-Aufwuchs-Interaktion, wie sie im Herbst und zeitigen Frühjahr anzutreffen ist. Terbutryn verursachte ab 6 µg/L eine deutliche Reduktion der Aufwuchsquantität, was indirekt das Wachstum und die Fettreserven der Grazer verringerte. Die Grazer zeigten ab 0,6 µg/L eine deutliche erhöhte Drift. Da bei dieser Konzentration noch keine Effekte auf die Aufwuchsbiomasse detektiert wurde, ist dies ein Indiz für verringerte Qualität des Aufwuchses. Insektzide werden verstärkt im Frühjahr ausgebracht und beeinflussen die Entwicklung der Grazer direkt. Das zweite Szenario untersuchte die Effekte des Insektizids lambda-Cyhalotrhin (LCH) auf die Grazer-Aufwuchs-Interaktion. LCH ist stark lipophil und adsorbiert schnell an organisches Material und Aufwüchse in Gewässer, weshalb es besonders für aufwuchsfressende Organismen bioverfügbar ist. Neben den erwarteten letalen Effekten wurden in Bereichen um 1 µg/g OC bereits subletale Effekte auf das Driftverhalten sowie das Wachstum der Grazer gefunden. Die Fettreserven waren ab ca. 0,01 µg/g OC reduziert, was auf verringerte Fraßaktivität in diesen niedrigen Konzentrationsbereichen schließen lässt. Die Analyse des Aufwuchses zeigte einen indirekt Effekt von LCH auf die Aufwuchsentwicklung, der einerseits auf die erhöhte Mortalität der Grazer aber auch auf LCH-induzierte Verhaltensänderungen zurückgeführt werden konnte. Das finale Szenario befasste sich mit den Effekten der kombinierten Exposition von Herbizid und Insektizid, wie sie im Lebenszyklus von R. semicolorata auftreten. Dabei zeigte sich entgegen der Erwartung keine erhöhte Mortalität durch die kombinierte Exposition. Die Ergebnisse weisen jedoch daraufhin, dass die Reduzierung der physiologischen Kondition der Grazer, durch die indirekten Effekte von Terbutryn, in subletalen Konzentrationsbereichen von LCH die Dauer bis zur Wiedererholung verlängert. Außerdem zeigte sich am Ende eine erhöhte Aufwuchsbiomasse, was eine reduzierte Leistung des Grazings durch die kombinierte Exposition indiziert. / The eutrophication of running water ecosystems leads especially in spring to an increase of benthic biofilms or aufwuchs, which reduces the infiltration of water into the river bed and, hence, disturb important ecological functions. Different studies already showed that invertebrate grazers of running water ecosystems are able to reduce the aufwuchs biomass effectively. This important ecological function, the benthic grazing, can therefore contribute to compensate the negative effects of eutrophication in lotic ecosystems. Relevant grazers are for instance the larvae of the mayfly Rhithrogena semicolorata, which reach high biomasses in streams and show a high feeding specialisation on aufwuchs. During their on year lasting life cycle the larvae of R. semicolorata are exposed to different pesticides, which can disturb their development. To evaluate the effects of pesticides on the development of this important grazer three exposition scenarios were performed following real exposure patterns from the environment. In the first scenarios the effects of a solely exposure with the herbicide Terbutryn on the grazer-aufwuchs-interaction was investigated, as it occurs preferably during autumn and spring. Terbutryn induced a clear reduction of aufwuchs quantity at 6 µg/L, which indirectly affected the growth and the energy storages of the grazers. Furthermore, the grazers showed an increased drift activity at 0.6 µg/L. Considering that the aufwuchs biomass was not affected at this low concentrations, the increased drift was interpreted as an indirect effect of reduced aufwuchs quantity. Inseciticides are preferably applied during spring and are able to disturb the development of grazers directly. The second scenario investigated therefore the effects of the insecticide lambda-Cyhalothrin (LCH) on the grazer-aufwuchs-interaction. LCH has a high lipophilicity and thus rapidly binds to organic matter or aufwuchs after entering aquatic ecosystems. This behaviour leads to a increased bioavailability of this substance to aufwuchs feeding organisms. Apart from the expected lethal effects, sublethal effects in form of increased drift and reduced grazer growth were found in a range of 1 µg/g OC LCH. Moreover, the energy storages of grazers were reduced at 0,01 µg/g OC, which is an indication of disturbed feeding behaviour at this low concentration. The analysis of the aufwuchs revealed additionally an indirect effect of LCH on the aufwuchs development, which was caused by increased grazer mortality and behavioural changes of the grazers induced by sublethal LCH concentrations. The final scenario aimed on the effects of a combined exposure of herbicide and insecticide, as it occurs during the life cycle of R. semicolorata. A increased mortality of grazers, due to the combinded exporsure, was not found. However, the results indicate that the reduction of the physiological condition by the indirect effect of Terbutryn extends the time until grazers recover from sublethal LCH exposure. Finally, also an increased aufwuchs biomass was found in treatments with combined exposure, indicating a reduced performance of grazers exposed to both substances.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The dual purpose wheat has the capacity to produce forage and grain, through the expression of morphological and bromatologic traits and yield components. Thus, the overall goal was to identify biometric models to understand the interrelationships between traits, direct and indirect selection in breeding wheat for dual purposes. The specific objectives of this study were to determine the canonical correlations between groups of morphological traits and grain yield, and identify the direction and the magnitude of the relationship; and identify the phenotypic relationships of cause and effect bromatologic between forage characters in wheat genotypes under different dual purpose cutting managements. The experiments were conducted in the growing seasons 2013 and 2014 in the experimental area of the Federal University of Santa Maria Campus Frederico Westphalen - RS. A randomized complete block design was used in three trials, the first experiment was arranged in a factorial: five genotypes (BRS Tarumã, BRS Umbu, BRS Figueira, BRS Guatambu and BRS 277) x four cutting managements (uncut, a cut, two cuts and three cuts). The second experiment was arranged in a factorial: Five genotypes (BRS Tarumã, BRS Umbu, BRS Figueira, BRS Guatambu and BRS 277) x Three cutting managements (first cut, second cut and third cut). The traits evaluated were: number of tillers per plant (AF), stem diameter of tillers (DAF), diameter of the main stem (DCP), number of fertile tillers (AFF), number of ears per square meter (ESPM), number of grains per ear (NGE), grain weight per ear (MGE), thousand grain weight (MMG), grain yield (RG), weight hectolitre (PH), green matter per hectare (MV), dry matter per hectare (MS), percentage of hemicellulose (HEM), cellulose (CEL), mineral matter (MM), neutral detergent fiber (FDN), acid detergent fiber (FDA), lignin (LIG), total carbohydrates (CT), carbohydrates no fiber carbohydrates (CNF), crude protein (PTN), and lipids (LIP). Groups of morphological traits and grain yield in wheat dual purpose reveal highly significant relationships. In the management at uncut and one cut wheat, associations are similarly established for both groups, by increasing the DCP, and determining the ESPM the increase, NGE and MGE, MMG, PH and RG. With two cuts the associations are established through the DAF, which influences an increase in MMG, PH and RG. Three cuts showed that the increase in AF increment the ESPM, NGE and MGE, MMG, PH and RG. The indirect selection aimed at increasing the PTN in the first cut can be based on CT, CNF and MV. The second cut provides indirect selection with LIG, CNF, MV and MS. The increase of PTN in the third cut can be obtained by indirect selection to the FDA, CEL, LIG, MM, MV and MS. Indirect selection through forage characters and bromatologic can be successful, since it considers the effect assigned to each cutting management. / O trigo duplo propósito apresenta capacidade de produzir forragem e grãos, através da expressão de caracteres morfológicos, bromatológicos e componentes do rendimento. Desta maneira, o objetivo geral foi identificar modelos biométricos que permitam compreender as inter-relações entre caracteres, e direcionar a seleção indireta no melhoramento genético de trigo duplo propósito. Os objetivos específicos deste trabalho foram: determinar as correlações canônicas entre grupos de caracteres morfológicos e do rendimento de grãos, e identificar o sentido e a magnitude das relações; e identificar as associações fenotípicas de causa e efeito entre caracteres forrageiros e bromatológicos em genótipos de trigo duplo propósito submetidos a diferentes manejos de corte.Os experimentos foram realizados nas safras agrícolas 2013 e 2014 na área experimental da Universidade Federal de Santa Maria Campus de Frederico Westphalen RS. Utilizou-se o delineamento de blocos ao acaso em três repetições, o primeiro experimento foi organizado em fatorial: Cinco genótipos (BRS Tarumã, BRS Umbu, BRS Figueira, BRS Guatambu e BRS 277) x Quatro manejos de corte (sem corte, um corte, dois cortes e três cortes). O segundo experimento foi organizado em fatorial: Cinco genótipos (BRS Tarumã, BRS Umbu, BRS Figueira, BRS Guatambu e BRS 277) x Três manejos de corte (primeiro corte, segundo corte e terceiro corte). Os caracteres avaliados foram: número de afilhos por planta (AF), diâmetro do colmo dos afilhos (DAF), diâmetro do colmo principal (DCP), número de afilhos férteis (AFF), número de espigas por metro quadrado (ESPM), número de grãos por espiga (NGE), massa de grãos por espiga (MGE), massa de mil grãos (MMG), rendimento de grãos (RG), peso hectolitro (PH), massa verde por hectare (MV), massa seca por hectare (MS), percentual de hemicelulose (HEM), celulose (CEL), material mineral (MM), fibras em detergente neutro (FDN), fibras em detergente ácido (FDA), lignina (LIG), carboidratos totais (CT), carboidratos não fibrosos (CNF), proteína bruta (PTN), e lipídios (LIP). Os grupos de caracteres morfológicos e de rendimento de grãos em trigo duplo propósito revelam relações altamente significativas. No manejo sem cortes e com um corte, associações são estabelecidas similarmente para ambos os grupos, através do aumento do DCP, sendo determinante ao acréscimo de ESPM, NGE e MGE, MMG, PH e RG. Com dois cortes as associações são estabelecidas através do DAF, que influencia o aumento da MMG, PH e RG. Com três cortes evidencia-se que o aumento do AF incrementam ESPM,NGE e MGE, MMG, PH e RG.A seleção indireta visando incrementar PTN no primeiro corte pode ser baseada nos CT,CNF e MV. O segundo corte proporciona a seleção indireta com a LIG, CNF, MV e MS. O incremento de PTN no terceiro corte poderá ser obtido através da seleção indireta com FDA, CEL, LIG, MM, MV e MS. A seleção indireta através dos caracteres forrageiros e bromatológicos pode ser realizada com sucesso, desde que se considere o efeito atribuído a cada manejo de corte.

Philosophiae Doctor - PhD / The income and employment multiplier effects of tourism- The case of Rwanda. A. NTIBANYURWA PhD Thesis, Department of Economics, University of the Western Cape. The growing popularity of developing countries as tourist destinations in recent years has stimulated a considerable body of research on the developmental benefits inherent in tourism. Developing countries have been attracting tourists mainly due to their natural resource endowments, considered a vital determinant in this newly-found source of their comparative advantage. After accounting for all the explicit and hidden costs linked to this natural resource-based tourism, the sustainable expansion of the tourism sector is claimed to be contributing substantially to economic growth. Studies to date have investigated the rising share of tourism in macroeconomic output, but have paid limited attention to the economic mechanisms through which tourism supposedly leads to broader development. This study seeks to contribute to filling this gap in our knowledge of the economic dynamics associated with tourism. More specifically, the goal is to shed light on the channels through which tourism contributes to economic growth and to derive tourism income and employment multipliers to estimate its developmental benefits for Rwanda. Our refined multipliers to capture the total effects of tourism to the economy confirm that through its powerful inter-sectoral linkages, tourism improves the economic wealth of many developing countries including Rwanda. Deeper analysis of the macroeconomic consequences of the expansion of the service sector however suggests that, under some conditions, this could exhibit “Dutch Disease” effects. Tourism generates substantial foreign earnings and its development is strongly correlated with the shrinkage of the traditional primary

Die Eutrophierung von Fließgewässern führt besonders im Frühjahr zur Zunahme der Biomasse des benthischen Aufwuchses. Dies kann zur reduzierter Infiltration von Wasser in die Gewässersohle führen und wichtige Funktionen von Fließgewässerökosystems stören. Verschiedene Studien konnten zeigen, dass invertebrate Weidegänger (Grazer) in der Lage sind die Biomasse des Aufwuchses in Fließgewässern effektiv zu reduzieren. Diese wichtige ökologische Funktion, das benthische Grazing, kann dazu beitragen negative Effekte der Eutrophierung in Fließgewässern zu kompensieren. Relevante invertebrate Grazer sind unter anderem die Larven der Eintagsfliege Rhithrogena semicolorata, die hohe Biomassen in Fließgewässern erreichen und eine hohe Spezialisierung auf Aufwuchs zeigen. Die Larven von R. semicolorata sind während ihres einjährigen Lebenszykluses Pestiziden ausgesetzt, welche ihre Entwicklung beeinträchtigen können. Um die Effekte von Pestiziden auf die Entwicklung dieser wichtigen Grazer zu untersuchen wurden drei Expositionsszenarien in Anlehnung an reale Bedingungen im Freiland untersucht. Das erste Szenario untersucht die Effekten einer Exposition mit dem Herbizid Terbutryn auf die Grazer-Aufwuchs-Interaktion, wie sie im Herbst und zeitigen Frühjahr anzutreffen ist. Terbutryn verursachte ab 6 µg/L eine deutliche Reduktion der Aufwuchsquantität, was indirekt das Wachstum und die Fettreserven der Grazer verringerte. Die Grazer zeigten ab 0,6 µg/L eine deutliche erhöhte Drift. Da bei dieser Konzentration noch keine Effekte auf die Aufwuchsbiomasse detektiert wurde, ist dies ein Indiz für verringerte Qualität des Aufwuchses. Insektzide werden verstärkt im Frühjahr ausgebracht und beeinflussen die Entwicklung der Grazer direkt. Das zweite Szenario untersuchte die Effekte des Insektizids lambda-Cyhalotrhin (LCH) auf die Grazer-Aufwuchs-Interaktion. LCH ist stark lipophil und adsorbiert schnell an organisches Material und Aufwüchse in Gewässer, weshalb es besonders für aufwuchsfressende Organismen bioverfügbar ist. Neben den erwarteten letalen Effekten wurden in Bereichen um 1 µg/g OC bereits subletale Effekte auf das Driftverhalten sowie das Wachstum der Grazer gefunden. Die Fettreserven waren ab ca. 0,01 µg/g OC reduziert, was auf verringerte Fraßaktivität in diesen niedrigen Konzentrationsbereichen schließen lässt. Die Analyse des Aufwuchses zeigte einen indirekt Effekt von LCH auf die Aufwuchsentwicklung, der einerseits auf die erhöhte Mortalität der Grazer aber auch auf LCH-induzierte Verhaltensänderungen zurückgeführt werden konnte. Das finale Szenario befasste sich mit den Effekten der kombinierten Exposition von Herbizid und Insektizid, wie sie im Lebenszyklus von R. semicolorata auftreten. Dabei zeigte sich entgegen der Erwartung keine erhöhte Mortalität durch die kombinierte Exposition. Die Ergebnisse weisen jedoch daraufhin, dass die Reduzierung der physiologischen Kondition der Grazer, durch die indirekten Effekte von Terbutryn, in subletalen Konzentrationsbereichen von LCH die Dauer bis zur Wiedererholung verlängert. Außerdem zeigte sich am Ende eine erhöhte Aufwuchsbiomasse, was eine reduzierte Leistung des Grazings durch die kombinierte Exposition indiziert. / The eutrophication of running water ecosystems leads especially in spring to an increase of benthic biofilms or aufwuchs, which reduces the infiltration of water into the river bed and, hence, disturb important ecological functions. Different studies already showed that invertebrate grazers of running water ecosystems are able to reduce the aufwuchs biomass effectively. This important ecological function, the benthic grazing, can therefore contribute to compensate the negative effects of eutrophication in lotic ecosystems. Relevant grazers are for instance the larvae of the mayfly Rhithrogena semicolorata, which reach high biomasses in streams and show a high feeding specialisation on aufwuchs. During their on year lasting life cycle the larvae of R. semicolorata are exposed to different pesticides, which can disturb their development. To evaluate the effects of pesticides on the development of this important grazer three exposition scenarios were performed following real exposure patterns from the environment. In the first scenarios the effects of a solely exposure with the herbicide Terbutryn on the grazer-aufwuchs-interaction was investigated, as it occurs preferably during autumn and spring. Terbutryn induced a clear reduction of aufwuchs quantity at 6 µg/L, which indirectly affected the growth and the energy storages of the grazers. Furthermore, the grazers showed an increased drift activity at 0.6 µg/L. Considering that the aufwuchs biomass was not affected at this low concentrations, the increased drift was interpreted as an indirect effect of reduced aufwuchs quantity. Inseciticides are preferably applied during spring and are able to disturb the development of grazers directly. The second scenario investigated therefore the effects of the insecticide lambda-Cyhalothrin (LCH) on the grazer-aufwuchs-interaction. LCH has a high lipophilicity and thus rapidly binds to organic matter or aufwuchs after entering aquatic ecosystems. This behaviour leads to a increased bioavailability of this substance to aufwuchs feeding organisms. Apart from the expected lethal effects, sublethal effects in form of increased drift and reduced grazer growth were found in a range of 1 µg/g OC LCH. Moreover, the energy storages of grazers were reduced at 0,01 µg/g OC, which is an indication of disturbed feeding behaviour at this low concentration. The analysis of the aufwuchs revealed additionally an indirect effect of LCH on the aufwuchs development, which was caused by increased grazer mortality and behavioural changes of the grazers induced by sublethal LCH concentrations. The final scenario aimed on the effects of a combined exposure of herbicide and insecticide, as it occurs during the life cycle of R. semicolorata. A increased mortality of grazers, due to the combinded exporsure, was not found. However, the results indicate that the reduction of the physiological condition by the indirect effect of Terbutryn extends the time until grazers recover from sublethal LCH exposure. Finally, also an increased aufwuchs biomass was found in treatments with combined exposure, indicating a reduced performance of grazers exposed to both substances.

To show how predaceous fish and dragonflies affect benthic community structure, we conducted enclosure experiments in the littoral zone of Bays Mountain Lake, Tennessee. A 'natural' benthic assemblage was subjected to all combinations of 2 densities of 3 predator treatments - small sunfish, 0 or 4/m2; large dragonfly larvae, 0 or 15/m2; and dragonfly eggs at 2 densities, 90 or 900/m2. Treatments were assigned randomly in each of 6 spatiotemporal blocks. Net effects of predation over 4 mo show that small sunfish had 'strong' effects (>50% reduction of densities) on triclads, large daphnid cladocerans, and snails, and 'moderate' effects (50% > reduction > 25%) on small dragonflies and ostracods; all these effects were statistically significant, except the one on ostracods. Large dragonflies had moderate non-significant effects on triclads and ostracods. There were no significant increases in prey density associated with fish predation; but chydorid cladocerans and midge larvae showed 'weak' non-significant increases that might be caused by 'indirect effects' of fish predation on invertebrate predators or grazers. There were only 2 significant interaction terms indicative of 'higher-order interactions': Fish X Dragonfly on the large daphnid Simocephalus, and Fish X Egg Density on snails, which were associated with relatively low probabilities. In both cases, the net effect of dragonflies was to reduce prey densities more when fish were present.

We are currently faced with the global challenge of conserving biological diversity while also increasing food production to meet the demands of a growing human population. Land-use change, primarily resulting from conversion to production land, is currently the leading cause of biodiversity loss. This occurs through habitat loss, fragmentation of remaining natural habitats, and resulting edge effects. Land-sparing and land-sharing approaches have been discussed as alternative ways to engineer landscapes to mitigate biodiversity loss while meeting production objectives. However, these represent extremes on a continuum of real-world landscapes, and it will be important to understand the mechanisms by which adjacent land use affects natural remnant ecosystems in order to make local land-management decisions that achieve conservation, as well as production, objectives. This thesis investigates the impact of juxtaposing production and natural forest on the community-wide interactions between lepidopteran herbivores and their parasitoids, as mediated by parasitoid spillover between habitats. The first and overarching objective was to determine whether herbivore productivity drives asymmetrical spillover of predators and parasitoids, primarily from managed to natural habitats, and whether this spillover alters trophic interactions in the recipient habitat. The study of trophic interactions at a community level requires understanding of both direct and indirect interactions. However, community-level indirect interactions are generally difficult to predict and measure, and these have therefore remained understudied. Apparent competition is an indirect interaction mechanism thought to be very important in structuring host-parasitoid assemblages. However, this is known primarily from studies of single species pairs, and its community-wide impacts are less clear. Therefore, my second objective was to determine whether apparent competition could be predicted for all species pairs within an herbivore assemblage, based on a measure of parasitoid overlap. My third objective was to determine whether certain host or parasitoid species traits can predict the involvement of those species in apparent competition. My key findings were that there is a net spillover of generalist predators and parasitoids from plantation to native forest, and that for generalists, this depends on herbivore abundance in the plantation forest. Herbivore populations across the edge were linked by shared parasitoids in apparent competition. Consequently, an experimental reduction of herbivore density in the plantation forest changed parasitism rates in the natural forest, as predicted based on parasitoid overlap. Finally, several host and parasitoid traits were identified that can predict the degree to which host or parasitoid species will be involved in apparent competition, a finding which may have extensive application in biological control, as well as in predicting spillover edge effects. Overall, this work suggests that asymmetrical spillover between production and natural habitats occurs in relation to productivity differences, with greater movement of predators and parasitoids in the managed-to-natural forest direction. The degree to which this affected species interactions has implications for landscape design to achieve conservation objectives in production landscapes.