TY - THES A1 - Danner, Nadja T1 - Honey bee foraging in agricultural landscapes T1 - Sammelverhalten von Honigbienen in der Agrarlandschaft N2 - 1. Today honey bee colonies face a wide range of challenges in modern agricultural landscapes which entails the need for a comprehensive investigation of honey bees in a landscape context and the assessment of environmental risks. Within this dissertation the pollen foraging of honey bee colonies is studied in different agricultural landscapes to gain insight into the use of pollen resources and the influence of landscape structure across the season. General suggestions for landscape management to support honey bees and other pollinators are derived. 2. Decoding of waggle dances and a subsequent spatial foraging analysis are used as methods in Chapters 4 and 5 to study honey bee colonies in agricultural landscapes. The recently developed metabarcoding of mixed pollen samples was applied for the first time in honey bee foraging ecology and allowed for a detailed analysis of pollen, that was trapped from honey bees in front hive entrances (Chapter 6). 3. Pollen identification through molecular sequencing and DNA barcoding has been proposed as an alternative approach to light microscopy, which still is a tedious and error-prone task. In this study we assessed mixed pollen probes through next-generation sequencing and developed a bioinformatic workflow to analyse these high-throughput data with a newly created reference database. To evaluate the feasibility, we compared results from classical identification based on light microscopy from the same samples with our sequencing results. Abundance estimations from sequencing data were significantly correlated with counted abundances through light microscopy. Next-generation sequencing thus presents a useful and efficient workflow to identify pollen at the genus and species level without requiring specialized palynological expert knowledge. 4. During maize flowering, four observation hives were placed in and rotated between 11 landscapes covering a gradient in maize acreage. A higher foraging frequency on maize fields compared to other landuse types showed that maize is an intensively used pollen resource for honey bee colonies. Mean foraging distances were significantly shorter for maize pollen than for other pollen origins, indicating that effort is put into collecting a diverse pollen diet. The percentage of maize pollen foragers did not increase with maize acreage in the landscape and was not reduced by grassland area as an alternative pollen resource. Our findings allow estimating the distance-related exposure risk of honey bee colonies to pollen from surrounding maize fields treated with systemic insecticides. 5. It is unknown how an increasing area of mass-flowering crops like oilseed rape (OSR) or a decrease of semi-natural habitats (SNH) change the temporal and spatial availability of pollen resources for honey bee colonies, and thus foraging distances and frequency in different habitat types. Sixteen observation hives were placed in and rotated between 16 agricultural landscapes with independent gradients of OSR and SNH area within 2 km to analyze foraging distances and frequencies. SNH and OSR reduced foraging distance at different spatial scales and depending on season, with possible benefits for the performance of honey bee colonies. Frequency of pollen foragers per habitat type was equally high for SNH, grassland and OSR fields, but lower for other crops and forest. In landscapes with a small proportion of SNH a significantly higher density of pollen foragers on SNH was observed, indicating the limitation of pollen resources in simple agricultural landscapes and the importance of SNH. 6. Quantity and diversity of collected pollen can influence the growth and health of honey bee colonies, but little is known about the influence of landscape structure on pollen diet. In a field experiment we rotated 16 honey bee colonies across 16 agricultural landscapes (see also Chapter 5), used traps to get samples of collected pollen and observed the intra-colonial dance communication to gain information about foraging distances. Neither the amount of collected pollen nor pollen diversity were related to landscape diversity. The revealed increase of foraging distances with decreasing landscape diversity suggests that honey bees compensate for a lower landscape diversity by increasing their pollen foraging range in order to maintain pollen amount and diversity. 7. Our results show the importance of diverse pollen resources for honey bee colonies in agricultural landscapes. Beside the risk of exposure to pesticides honey bees face the risk of nutritional deficiency with implications for their health. By modifying landscape composition and therefore availability of resources we are able to contribute to the wellbeing of honey bees. Agri-environmental schemes aiming to support pollinators should focus on possible spatial and temporal gaps in pollen availability and diversity in agricultural landscapes. N2 - 1. Honigbienen stehen heutzutage vor einer Vielzahl von Herausforderungen in der modernen Agrarlandschaft, was umfassende Untersuchungen von Honigbienen im Landschafskontext erforderlich macht. Im Rahmen dieser Arbeit wurde das Pollensammeln von Honigbienenvölkern in verschiedenen Agrarlandschaften studiert, um Einblick in die Nutzung von Pollenressourcen und auf den Einfluss der Landschaftsstruktur zu gewinnen. 2. Die Dekodierung von Schwänzeltänzen und eine anschließende räumliche Analyse des Sammelverhaltens werden als Methoden in den Kapiteln 4 und 5 eingesetzt, um Bienenvölker in Agrarlandschaften zu untersuchen. Das kürzlich entwickelte Metabarcoding von gemischten Pollenproben wurde zum ersten Mal in der Honigbienenökologie angewandt und ermöglichte eine detaillierte Analyse von Pollenproben, die per Pollenfallen vor den Stockeingängen gesammelt wurden (Kapitel 6). 3. Pollenbestimmung durch molekulare Sequenzierung und DNA Barcoding wurde als Alternative zur Lichtmikroskopie vorgeschlagen, die immer noch sehr mühsam und fehlerbehaftet ist. In dieser Studie bestimmten wir gemischte Pollenproben durch Next-Generation-Sequenzierung und entwickelten einen bioinformatischen Arbeitsablauf um diese Hochdurchsatz-Daten mit einer neu kreierten Referenzdatanbank zu analysieren. Um die Durchführbarkeit zu evaluieren verglichen wir Ergebnisse aus der klassischen Identifizierung via Lichtmikroskopie derselben Proben mit unseren Sequenzier-Ergebnissen. Häufigkeitsschätzungen auf Basis der Sequenzierdaten waren signifikant mit den gezählten Häufigkeiten via Lichtmikroskopie korreliert. Next-Generation-Sequenzierung stellt daher einen nützlichen und effizienten Arbeitsablauf dar, um Pollen auf dem Gattungs- und Artniveau zu bestimmen ohne spezielles palynologisches Expertenwissen zu benötigen. 4. Während der Maisblüte wurden vier Beobachtungsstöcke in 11 Landschaften mit einem Maisflächengradienten platziert und zwischen diesen rotiert. Maisfelder wurden intensiver genutzt als Flächen anderer Landnutzungstypen. Die mittleren Sammeldistanzen waren signifikant niedriger für Maispollen als Pollen anderer Herkunft, was darauf hinweist, dass Aufwand in das Sammeln einer diversen Pollendiät gesetzt wird. Der Anteil an Maispollensammlerinnen stieg nicht mit der Maisanbaufläche in der Landschaft und wurde nicht durch Grünlandfläche als alternative Pollenressource reduziert. Unsere Ergebnisse ermöglichen die Schätzung des entfernungsbezogenen Expositionsrisikos von Honigbienenvölker auf Pollen aus den umliegenden Maisfeldern, die mit systemischen Insektiziden behandelt werden. 5. Es ist nicht bekannt, wie eine Zunahme von Massentrachten wie Raps (OSR) oder eine Abnahme von halbnatürlichen Habitaten (SNH) die zeitliche und räumliche Verfügbarkeit von Pollenressourcen für die Honigbienen, und damit Sammeldistanzen und -frequenzen in verschiedenen Lebensraumtypen verändert. Sechzehn Beobachtungsstöcke wurden in 16 Agrarlandschaften mit unabhängigen Gradienten an OSR- und SNH-Fläche innerhalb von 2 km platziert und regelmäßig rotiert, um Sammeldistanzen und -frequenzen zu analysieren. SNH und OSR reduzierten die Sammeldistanzen auf verschiedenen räumlichen Skalen und je nach Saison, mit möglichen Vorteilen für die Leistungsfähigkeit von Bienenvölkern. Die Häufigkeit der Pollensammler pro Habitattyp war gleich hoch für SNH, Grünland und OSR, aber niedriger für andere Kulturen und Wald. In Landschaften mit einem kleinen Anteil von SNH wurde eine deutlich höhere Dichte von Pollensammlerinnen auf SNH beobachtet, was auf die Begrenzung der Pollenressourcen in einfachen Agrarlandschaften und die Bedeutung von SNH hinweist. 6. Menge und Diversität des gesammelten Pollens können das Wachstum und die Gesundheit von Honigbienenvölkern beeinflussen, aber es ist wenig über den Einfluss der Landschaftsstruktur auf die Pollendiät bekannt. In einem Feldexperiment rotierten wir 16 Honigbienenkolonien über 16 Agrarlandschaften (siehe auch Kapitel 5), nutzten Pollenfallen um Proben des gesammelten Pollens zu nehmen und beobachteten die intrakoloniale Tanzkommunikation, um Informationen über die Sammeldistanzen zu erhalten. Weder Pollenmenge noch -diversität waren von der Landschaftsdiversität abhängig. Der offenbarte Anstieg von Sammeldistanzen mit abnehmender Landschaftsdiversität legt nahe, dass Honigbienen durch die Erweiterung des Pollensammelbereichs eine niedrigere Landschaftsdiversität kompensieren, um Pollenmenge und -diversität zu erhalten. 7. Unsere Ergebnisse zeigen die Bedeutung eines diversen Pollenangebots für Bienenvölker in der Agrarlandschaft. Neben dem Risiko einer Exposition gegenüber Pestiziden, stehen Bienenvölker vor der Gefahr von Mangelernährung mit Auswirkungen auf ihre Gesundheit. Durch eine Änderung der Landschaftzusammensetzung und damit der Verfügbarkeit von Ressourcen können wir zum Wohlergehen der Honigbienen beitragen. Agrarumweltmaßnahmen mit dem Ziel Bestäuber zu unterstützen, sollten sich auf mögliche räumliche und zeitliche Lücken in der Pollenverfügbarkeit und Vielfalt in der Agrarlandschaft konzentrieren. KW - Apis mellifera KW - Zea mays KW - Resource Use KW - Exposure Risk KW - Oilseed Rape KW - foraging distances KW - Sammeldistanzen KW - semi-natural habitat KW - halbnatürliche Habitate KW - next-generation sequencing KW - pollen KW - Pollen KW - Next-Generation Sequenzierung KW - Landschaftsstruktur KW - landscape structure Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-139322 ER - TY - JOUR A1 - Steijven, Karin A1 - Spaethe, Johannes A1 - Steffan-Dewenter, Ingolf A1 - Härtel, Stephan T1 - Learning performance and brain structure of artificially-reared honey bees fed with different quantities of food JF - PeerJ N2 - Background Artificial rearing of honey bee larvae is an established method which enables to fully standardize the rearing environment and to manipulate the supplied diet to the brood. However, there are no studies which compare learning performance or neuroanatomic differences of artificially-reared (in-lab) bees in comparison with their in-hive reared counterparts. Methods Here we tested how different quantities of food during larval development affect body size, brain morphology and learning ability of adult honey bees. We used in-lab rearing to be able to manipulate the total quantity of food consumed during larval development. After hatching, a subset of the bees was taken for which we made 3D reconstructions of the brains using confocal laser-scanning microscopy. Learning ability and memory formation of the remaining bees was tested in a differential olfactory conditioning experiment. Finally, we evaluated how bees reared with different quantities of artificial diet compared to in-hive reared bees. Results Thorax and head size of in-lab reared honey bees, when fed the standard diet of 160 µl or less, were slightly smaller than hive bees. The brain structure analyses showed that artificially reared bees had smaller mushroom body (MB) lateral calyces than their in-hive counterparts, independently of the quantity of food they received. However, they showed the same total brain size and the same associative learning ability as in-hive reared bees. In terms of mid-term memory, but not early long-term memory, they performed even better than the in-hive control. Discussion We have demonstrated that bees that are reared artificially (according to the Aupinel protocol) and kept in lab-conditions perform the same or even better than their in-hive sisters in an olfactory conditioning experiment even though their lateral calyces were consistently smaller at emergence. The applied combination of experimental manipulation during the larval phase plus subsequent behavioral and neuro-anatomic analyses is a powerful tool for basic and applied honey bee research. KW - nutrition KW - cognition KW - neuroanatomy KW - differential olfactory conditioning KW - mushroom bodies KW - proboscis extension reflex KW - confocal laser scanning microscopy KW - Apis mellifera KW - brain development KW - morphometry Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170137 VL - 5 IS - e3858 ER - TY - JOUR A1 - Drescher, Nora A1 - Klein, Alexandra-Maria A1 - Neumann, Peter A1 - Yañez, Orlando A1 - Leonhardt, Sara D. T1 - Inside Honeybee Hives: Impact of Natural Propolis on the Ectoparasitic Mite Varroa destructor and Viruses JF - Insects N2 - Social immunity is a key factor for honeybee health, including behavioral defense strategies such as the collective use of antimicrobial plant resins (propolis). While laboratory data repeatedly show significant propolis effects, field data are scarce, especially at the colony level. Here, we investigated whether propolis, as naturally deposited in the nests, can protect honeybees against ectoparasitic mites Varroa destructor and associated viruses, which are currently considered the most serious biological threat to European honeybee subspecies, Apis mellifera, globally. Propolis intake of 10 field colonies was manipulated by either reducing or adding freshly collected propolis. Mite infestations, titers of deformed wing virus (DWV) and sacbrood virus (SBV), resin intake, as well as colony strength were recorded monthly from July to September 2013. We additionally examined the effect of raw propolis volatiles on mite survival in laboratory assays. Our results showed no significant effects of adding or removing propolis on mite survival and infestation levels. However, in relation to V. destructor, DWV titers increased significantly less in colonies with added propolis than in propolis-removed colonies, whereas SBV titers were similar. Colonies with added propolis were also significantly stronger than propolis-removed colonies. These findings indicate that propolis may interfere with the dynamics of V. destructor-transmitted viruses, thereby further emphasizing the importance of propolis for honeybee health. KW - social immunity KW - Apis mellifera KW - deformed wing virus KW - plant-insect interactions KW - resin KW - sacbrood virus Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-171164 VL - 8 IS - 1 ER - TY - JOUR A1 - Nürnberger, Fabian A1 - Steffan-Dewenter, Ingolf A1 - Härtel, Stephan T1 - Combined effects of waggle dance communication and landscape heterogeneity on nectar and pollen uptake in honey bee colonies JF - PeerJ N2 - The instructive component of waggle dance communication has been shown to increase resource uptake of Apis mellifera colonies in highly heterogeneous resource environments, but an assessment of its relevance in temperate landscapes with different levels of resource heterogeneity is currently lacking. We hypothesized that the advertisement of resource locations via dance communication would be most relevant in highly heterogeneous landscapes with large spatial variation of floral resources. To test our hypothesis, we placed 24 Apis mellifera colonies with either disrupted or unimpaired instructive component of dance communication in eight Central European agricultural landscapes that differed in heterogeneity and resource availability. We monitored colony weight change and pollen harvest as measure of foraging success. Dance disruption did not significantly alter colony weight change, but decreased pollen harvest compared to the communicating colonies by 40%. There was no general effect of resource availability on nectar or pollen foraging success, but the effect of landscape heterogeneity on nectar uptake was stronger when resource availability was high. In contrast to our hypothesis, the effects of disrupted bee communication on nectar and pollen foraging success were not stronger in landscapes with heterogeneous compared to homogenous resource environments. Our results indicate that in temperate regions intra-colonial communication of resource locations benefits pollen foraging more than nectar foraging, irrespective of landscape heterogeneity. We conclude that the so far largely unexplored role of dance communication in pollen foraging requires further consideration as pollen is a crucial resource for colony development and health. KW - Apis mellifera KW - orientation KW - recruitment KW - landscape ecology KW - foraging behaviour KW - floral resource distribution Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170813 VL - 5 IS - e3441 ER -