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Institut
A solid knowledge about nature is essential to understand the consequences of biodiversity loss, the limitation of natural resources and the need for a sustainable development. Inspired by these challenges, the researcher investigated in her dissertation seed predation, an important ecosystem function, as part of citizen science project. As seed predation has only rarely been investigated along urban-rural gradients and to integrate the question if the background (urban vs. rural) of primary school children affects their environmental knowledge, she selected study sites in and around Lüneburg and Hamburg, in Northern Germany. In her ecological experiments, it was found that slugs are important seed predators that independently of urbanization predated about 30% of all seeds in the anthropogenically used landscapes investigated. Also, for the first time, primary school children could be integrated in a citizen science approach into this research and it could be shown that even seven year old children can record data as reliable as a scientist. Finally, the researcher investigated the native species knowledge from the children taking part as citizen scientists in her research, considering possible differences due to their urban or rural background. Contrary to her expectation, the urban or rural background had no significant effect on the species knowledge. However, the work provides a good foundation to transfer the approach of introducing a basic foundation of a taxonomical species concept in primary school to foster further understanding on biodiversity and ecosystem functions.
Loss of natural and semi-natural habitat due to increasing human land use for agriculture and housing has led to widespread declines in bee pollinator diversity and abundance, which raised global concerns about the stability of pollination services. Bee population dynamics depend on floral resource diversity and availability in the surrounding landscape, and loss of plant biodiversity may thus directly impair the fitness of individual bee species. However, whether and how plant and resource diversity and availability affect foraging patterns, resource intake, resource quantity and nutrient quality and ultimately fitness of generalist social bees remains unclear. In this thesis, we placed hives of the Australian eusocial stingless bee Tetragonula carbonaria (Apidae, Meliponini) in natural habitat (subtropical forests) and two landscapes differently altered by humans (suburban gardens and macadamia plantations), varying in plant species richness, resource abundance and respective habitat patch size. Foraging patterns and resource intake were compared between landscapes in different seasons and colony growth and fitness were monitored over two and a half years. Bee foraging activity, pollen and sugar intake, diversity of collected pollen and resin resources, resource quantity (colony food stores), colony fitness (brood volume, queenand worker reproduction) and colony growth overwhelmingly increased with plant species richness in the surrounding habitat. However, plant species richness and thus bee fitness was highest in gardens, not in natural forests, as bees in gardens benefited from the continuous floral resource availability of both natural and exotic plants across seasons. In contrast, foraging rates and success, forager orientation and consequently colony fitness was largely reduced in plantations. While bees maximized diversity of collected resources, collecting more diverse resources did however not increase resource functionality and nutritional quality, which appeared to be primarily driven by the surrounding plant community in our study. Conversely, individual worker fitness (body fat and size) was not affected by available resource diversity and abundance, showing that colonies seem not to increase the nutritional investment in single workers, but in overall worker population size. This thesis consequently revealed the outstanding role of plant biodiversity as a key driver of (social) bee fitness by providing more foraging resources, even when only small but florally diverse patches are available.
The worldwide decline of plant and insect species during the last decades has far-reaching consequences for the functionality of ecosystems and their inherent processes. Pollination as one of them is an indispensable ecosystem service for human wellbeing. However, an increasing number of pollinator and plant species are threatened by multiple, interacting, and sometimes synergistic causes that are becoming a growing threat to ecosystem functioning. Given the loss of plant species diversity, it is increasingly difficult for pollinators to find food throughout the year. Therefore, this study analyses the influence of plant diversity on pollinators. The study was conducted in the course of the Jena Experiment, which is a long-term biodiversity experiment (since 2002) with 60 plant species, common to Central European Arrhenatherum grasslands. With a plant diversity gradient of 1, 2, 4, 8, 16, and 60 plant species per plot, time-series data resulted from a wide range of ecosystem processes, ranging from productivity, decomposition, C-storage, and N-storage to herbivory, and pollination. These were studied to investigate the mechanisms underlying the relationships between biodiversity and ecosystem processes. Chapter 2 studies the spatio-temporal distribution of pollinators on flowers along an experimental plant diversity gradient. In particular, the spatial pollinator behaviour was examined. Chapters 3 and 4 continues on the chemical composition of flower nectar (nectar) of various plant species. The chemical composition of the nectar was analysed for the two most important macronutrients, carbohydrates (C) and amino acids (AA), using high performance liquid chromatography (HPLC). Subsequently, their contents were analysed in terms of concentration, proportional content and the ratio of carbohydrates to amino acids (C:AA). In Chapter 3, the nectar of 34 plant species from the grasslands of the Jena Experiment was compared. In Chapter 4, nectar was investigated in the context of diversity effects on the example of the plant species Field Scabious, Knautia arvensis. It was analysed to what extent the nectar quality (nutrient content) differs between plant individuals of one species. Overall, these studies indicate how fragile plant-pollinator interactions are but also how important plant species-rich grasslands are to support plant-pollinator interactions. Increased plant species diversity is essential to ensure the availability of flowering resources throughout the year. Pollinators, such as honeybees, bumblebees, solitary bees, and hoverflies can use the niches in time and in vertical space complementarily. However, in plant species-poor grasslands there may be more niche overlaps, which is probably due to a reduced availability of resources. This points to the need to include different plant species belonging to different plant families, whose nectar may have evolved in response to morphological flower traits and metabolic pathways. Therefore plant species diversity can supply pollinators with nectar differing in carbohydrate and amino acid content and thus differing in quality. Also C-AA ratios have proven to be a useful measurement to reveal differences between plant species. In addition, C:AA ratios were not differing in nectar of K. arvensis individuals growing in different plant species richness levels, although their nectar seemed to be more attractive in mixtures with 16 plant species, likely due to higher content of essential and phagostimulatory amino acids than in plant species-poor mixtures.
Neben optischen und akustischen Reizen werden verschiedenste Chemikalien für den Austausch von Informationen zwischen Lebewesen benutzt. Sie signalisieren Nahrungsquellen, Geschlechtspartner, Konkurrenten, Feinde und vieles mehr. Chemikalien, die für den Austausch von Informationen benutzt werden, wer- den als Botenstoffe, englisch Infochemicals, bezeichnet. Die Eigenschaft einer Substanz, als Botenstoff zu wirken, wird als ”Infochemical Effect“ bezeichnet. Zu diesen Botenstoffen gehören auch viele Substanzen, die als Duftstoffe in Produkten des täglichen Bedarfs eingesetzt werden. Viele Produkte zur Des- infektion, Reinigung und Körperpflege enthalten Duftstoffe, um unangenehme Gerüche zu maskieren und das Ergebnis zu unterstreichen. Der überwiegende Teil dieser Stoffe gelangt, wenn sie bestimmungsgemäß angewendet werden, ins Abwasser. Wenn sie nicht durch die Abwasserbehandlung mineralisiert werden, können sie in die aquatische Umwelt gelangen, als Botenstoffe Organismen er- reichen und diese zu falschen Reaktionen veranlassen. Diese Störung wird als ”anthropogenic Infochemical Effect“ bezeichnet. Über einen Zeitraum von drei Jahren wurde für das Universitätsklinikum Freiburg (UKF) und die Friedrich-Husemann-Klinik (FHK) der Einkauf von Duftstoffen aus Wasch-, Reinigungs- und Desinfektionsmitteln bilanziert. Aus- gewählte, am UKF verwendete Produkte wurden mit Festphasen-Mikroextraktion (Solid Phase Micro Extraction) (SPME), Gaschromatographie gekoppelt mit Flammenionisationsdetektor (GC-FID) und Gaschromatograph gekoppelt mit Massenspektrometer (GC-MS) auf die in ihnen enthaltenen Duftstoffe unter- sucht. Die gefundenen Duftstoffe wurden auf ihre biologische Abbaubarkeit und ihr Verhalten bei UV-Bestrahlung untersucht. Zusätzlich wurden die be- rechnete regionale Umweltkonzentration (Predicted Environmental Concentra- tion) (PECregional) und, soweit Daten zur Toxizität vorlagen, auch der Risiko- quotient (Risk Characterization Ratio) (RCR) berechnet. Für das UKF war der Verbrauch pro Bett und Tag und die Abwasserkonzentration höher als an der FHK. Die Duftstoffe wurden bei beiden Kliniken über dieselben Produktgruppen eingetragen. Die Daten aus der Bilanzierung mit EUSES dagegen ergab für die meisten untersuchten Substanzen eine wesentlich geringere Umweltkonzentration. Keiner der Duftstoffe erreichte einen RCR über eins. In den Abbautests nach Norm 301D und 301F der Gemeinschaft für wirtschaftliche Zusammenarbeit und Entwicklung (Organisation for Economic Co-operation and Developement) (OECD) erwiesen sich einige Duftstoffe als nicht leicht biologisch abbaubar. Für den Duftstoff 2-(- 4-tert-Butylbenzyl)propionaldehyd konnten verschiedene Transformationsprodukte gefunden werden. Zwei dieser Transformationsprodukte konnten identifiziert und entsprechende Standards synthetisiert werden. Die Modellierung toxischer Effekte durch Programme, die quantitative Struktur-Wirkungs-Beziehung (Quantitative Structure-Activity Relationship) (QSAR) Berechnungen verwenden ergab, dass die Transformationsprodukte höhere Aktivitäten als die Ursprungssubstanz besitzen. Für einige der untersuchten Substanzen wurden Wirk- schwellen für einen Infochemical Effect ermittelt. Keiner der Duftstoffe erreichte mit seinem PECregional diese Wirkschwelle. Ein anthropogener Infochemical Ef- fect kann aber nicht ausgeschlossen werden, da Daten zu Wirkschwellen nur für einzelne Organismen gefunden werden konnten.
Social insects like honeybees (Apis mellifera) and stingless bees (Apidae: Meliponini) face a relatively high risk to be attacked by pests and pathogens. To decrease the risk of infection, in addition to an innate immune system, these species have evolved various cooperative defense mechanisms which contribute to the overall health of the colonies and are therefore also referred to as social immunity. The collection and use of plant resin is another important strategy of social immunity. Resin is a sticky, often aromatic substance with antimicrobial and deterrent properties secreted by plants for protection of the vegetative tissue. Honeybees and stingless bees take advantage of these properties by using resins for nest construction (often mixtures of resin and wax called "propolis" or "cerumen") and as defense against pests and pathogens. Plant resins, thus, play a crucial role for the ecology of these species and are an important resource for them. Nevertheless, how bees exploit available resin sources and if resin collection can protect colonies from diseases received comparatively little attention in the past. Therefore the aim of this thesis is to provide new insights into the plant origin and significance as well as the influence of resin resource diversity on bee colony health. For honeybees (A. mellifera) in temperate regions, precise information about which resin sources they use is largely lacking. By chemical comparing bee-collected resins and tree resins, the researcher traced back the resin sources used by individual bees. Results show that honeybees collect distinct resin types that are related to different tree species (several poplar species: Populus balsamifera, P. xcanadensis; Betula alba; Aesculus hippocastanum; several poplar species). With this study, the author provided the first evidence, that A. mellifera in temperate regions use a variety of different tree species as resin sources and, moreover, show preferences for specific resin sources. Furthermore, the researcher conducted an experimental field study in which she investigated whether propolis, as it is naturally deposited in the nests, can protect honeybee colonies against some of the most important pathogens (Varroa destructor mite, Deformed Wing Virus). The results of this study showed that propolis in (semi-) natural conditions can increase the disease resistance of honeybee colonies, underscoring the importance of resins for honeybee health. Resin collection by stingless bees is comparatively well studied and it is known that these species commonly forage on a variety of different plant species. To increase knowledge on whether and how bees may profit from a diversity of resin resources, the researcheer tested how the protective function of a resin varied among different sources (and their mixtures) and various potential aggressors (predators, parasites and pathogens). The results of this study revealed that resins from different trees vary in their effectivity against different target organisms. Moreover, resin blends were more effective than some of the individual resins, suggesting that bees can benefit from a variety of resin resources. In summary, honeybees in temperate regions, similar to tropical stingless bees, use a variety of different tree species as resin sources. Because resins from different tree species varied in their protective function, this indicates that bees can profit from a variety of different resins/resin sources by improving the defense against diverse pests and pathogens. Conversely, the lack of resin had a negative impact on the disease resistance of colonies. Consequently, availability as well as the variety of suitable resin sources is of great importance for the health of bees.