TY - JOUR A1 - Otieno, Mark A1 - Karpati, Zsolt A1 - Peters, Marcell K. A1 - Duque, Laura A1 - Schmitt, Thomas A1 - Steffan-Dewenter, Ingolf T1 - Elevated ozone and carbon dioxide affects the composition of volatile organic compounds emitted by Vicia faba (L.) and visitation by European orchard bee (Osmia cornuta) JF - PLoS One N2 - Recent studies link increased ozone (O\(_3\)) and carbon dioxide (CO\(_2\)) levels to alteration of plant performance and plant-herbivore interactions, but their interactive effects on plant-pollinator interactions are little understood. Extra floral nectaries (EFNs) are essential organs used by some plants for stimulating defense against herbivory and for the attraction of insect pollinators, e.g., bees. The factors driving the interactions between bees and plants regarding the visitation of bees to EFNs are poorly understood, especially in the face of global change driven by greenhouse gases. Here, we experimentally tested whether elevated levels of O\(_3\) and CO\(_2\) individually and interactively alter the emission of Volatile Organic Compound (VOC) profiles in the field bean plant (Vicia faba, L., Fabaceae), EFN nectar production and EFN visitation by the European orchard bee (Osmia cornuta, Latreille, Megachilidae). Our results showed that O\(_3\) alone had significant negative effects on the blends of VOCs emitted while the treatment with elevated CO\(_2\) alone did not differ from the control. Furthermore, as with O\(_3\) alone, the mixture of O\(_3\) and CO\(_2\) also had a significant difference in the VOCs’ profile. O\(_3\) exposure was also linked to reduced nectar volume and had a negative impact on EFN visitation by bees. Increased CO\(_2\) level, on the other hand, had a positive impact on bee visits. Our results add to the knowledge of the interactive effects of O\(_3\) and CO\(_2\) on plant volatiles emitted by Vicia faba and bee responses. As greenhouse gas levels continue to rise globally, it is important to take these findings into consideration to better prepare for changes in plant-insect interactions. KW - Volatile Organic Compound (VOC) KW - Vicia faba (L.) KW - European orchard bee (Osmia cornuta) KW - carbon dioxide (CO2) KW - ozone (O3) KW - bees KW - flowering plants KW - plant-insect interactions KW - flowers KW - plant physiology KW - plant-herbivore interactions Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-350020 VL - 18 IS - 4 ER - TY - THES A1 - Mayr, Antonia Veronika T1 - Following Bees and Wasps up Mt. Kilimanjaro: From Diversity and Traits to hidden Interactions of Species T1 - Auf den Spuren von Bienen und Wespen auf den Kilimandscharo: Eine Studie über die Diversität, Merkmale und verborgenen Wechselwirkungen zwischen Arten N2 - Chapter 1 – General Introduction One of the greatest challenges of ecological research is to predict the response of ecosystems to global change; that is to changes in climate and land use. A complex question in this context is how changing environmental conditions affect ecosystem processes at different levels of communities. To shed light on this issue, I investigate drivers of biodiversity on the level of species richness, functional traits and species interactions in cavity-nesting Hymenoptera. For this purpose, I take advantage of the steep elevational gradient of Mt. Kilimanjaro that shows strong environmental changes on a relatively small spatial scale and thus, provides a good environmental scenario for investigating drivers of diversity. In this thesis, I focus on 1) drivers of species richness at different trophic levels (Chapter 2); 2) seasonal patterns in nest-building activity, life-history traits and ecological rates in three different functional groups and at different elevations (Chapter 3) and 3) changes in cuticular hydrocarbons, pollen composition and microbiomes in Lasioglossum bees caused by climatic variables (Chapter 4). Chapter 2 – Climate and food resources shape species richness and trophic interactions of cavity-nesting Hymenoptera Drivers of species richness have been subject to research for centuries. Temperature, resource availability and top-down regulation as well as the impact of land use are considered to be important factors in determining insect diversity. Yet, the relative importance of each of these factors is unknown. Using trap nests along the elevational gradient of Mt. Kilimanjaro, we tried to disentangle drivers of species richness at different trophic levels. Temperature was the major driver of species richness across trophic levels, with increasing importance of food resources at higher trophic levels in natural antagonists. Parasitism rate was both related to temperature and trophic level, indicating that the relative importance of bottom-up and top-down forces might shift with climate change. Chapter 3 – Seasonal variation in the ecology of tropical cavity-nesting Hymenoptera Natural populations fluctuate with the availability of resources, presence of natural enemies and climatic variations. But tropical mountain seasonality is not yet well investigated. We investigated seasonal patterns in nest-building activity, functional traits and ecological rates in three different insect groups at lower and higher elevations separately. Insects were caught with trap nests which were checked monthly during a 17 months period that included three dry and three rainy seasons. Insects were grouped according to their functional guilds. All groups showed strong seasonality in nest-building activity which was higher and more synchronised among groups at lower elevations. Seasonality in nest building activity of caterpillar-hunting and spider-hunting wasps was linked to climate seasonality while in bees it was strongly linked to the availability of flowers, as well as for the survival rate and sex ratio of bees. Finding adaptations to environmental seasonality might imply that further changes in climatic seasonality by climate change could have an influence on life-history traits of tropical mountain species. Chapter 4 – Cryptic species and hidden ecological interactions of halictine bees along an elevational Gradient Strong environmental gradients such as those occurring along mountain slopes are challenging for species. In this context, hidden adaptations or interactions have rarely been considered. We used bees of the genus Lasioglossum as model organisms because Lasioglossum is the only bee genus occurring with a distribution across the entire elevational gradient at Mt. Kilimanjaro. We asked if and how (a) cuticular hydrocarbons (CHC), which act as a desiccation barrier, change in composition and chain length along with changes in temperature and humidity (b), Lasioglossum bees change their pollen diet with changing resource availability, (c) gut microbiota change with pollen diet and climatic conditions, and surface microbiota change with CHC and climatic conditions, respectively, and if changes are rather influenced by turnover in Lasioglossum species along the elevational gradient. We found physiological adaptations with climate in CHC as well as changes in communities with regard to pollen diet and microbiota, which also correlated with each other. These results suggest that complex interactions and feedbacks among abiotic and biotic conditions determine the species composition in a community. Chapter 5 – General Discussion Abiotic and biotic factors drove species diversity, traits and interactions and they worked differently depending on the functional group that has been studied, and whether spatial or temporal units were considered. It is therefore likely, that in the light of global change, different species, traits and interactions will be affected differently. Furthermore, increasing land use intensity could have additional or interacting effects with climate change on biodiversity, even though the potential land-use effects at Mt. Kilimanjaro are still low and not impairing cavity-nesting Hymenoptera so far. Further studies should address species networks which might reveal more sensitive changes. For that purpose, trap nests provide a good model system to investigate effects of global change on multiple trophic levels and may also reveal direct effects of climate change on entire life-history traits when established under different microclimatic conditions. The non-uniform effects of abiotic and biotic conditions on multiple aspects of biodiversity revealed with this study also highlight that evaluating different aspects of biodiversity can give a more comprehensive picture than single observations. N2 - Kapitel 1 – Allgemeine Einführung Eine der größten Herausforderungen der ökologischen Forschung ist es, die Reaktion der Ökosysteme auf den globalen Wandel, d.h. auf Veränderungen von Klima und Landnutzung, vorherzusagen. Eine komplexe Frage in diesem Zusammenhang ist, wie sich verändernde Umweltbedingungen auf die Ökosystemprozesse auf verschiedenen Ebenen von Gemeinschaften auswirken. Um dieses Thema näher zu beleuchten, untersuche ich die Triebkräfte der Biodiversität auf der Ebene des Artenreichtums, der funktionellen Eigenschaften und der Wechselwirkungen zwischen Arten bei Hautflüglern, die in Hohlräumen nisten. Zu diesem Zweck nutze ich den steilen Höhengradienten des Kilimandscharo, der starke Umweltveränderungen auf relativ kleinem Raum mit sich bringt und somit ein gutes System für die Untersuchung von Triebkräften der biologischen Vielfalt bietet. In dieser Arbeit konzentriere ich mich auf 1) Triebkräfte des Artenreichtums auf verschiedenen trophischen Ebenen (Kapitel 2); 2) saisonale Muster in der Nestbauaktivität, lebensgeschichtliche Merkmale und ökologische Raten in drei verschiedenen funktionellen Gruppen und in verschiedenen Höhenlagen (Kapitel 3) und 3) Veränderungen in kutikulären Kohlenwasserstoffen, Pollenzusammensetzung und Mikrobiomen bei Lasioglossum Bienen, die durch klimatische Faktoren verursacht werden (Kapitel 4). Kapitel 2 – Klima und Nahrungsressourcen prägen den Artenreichtum und die trophischen Wechselwirkungen von hohlraumnistenden Hautflüglern Die Triebkräfte des Artenreichtums werden seit Jahrhunderten erforscht. Temperatur, Ressourcenverfügbarkeit und Top-Down-Regulierung sowie die Auswirkungen der Landnutzung werden als wichtige Faktoren für die Bestimmung der Insektenvielfalt angesehen. Die relative Bedeutung jedes dieser Faktoren ist jedoch unbekannt. Mit Hilfe von Nisthilfen entlang des Höhengradienten des Kilimandscharo versuchten wir, die Triebkräfte des Artenreichtums auf verschiedenen trophischen Ebenen zu enträtseln. Die Temperatur war der Hauptfaktor für den Artenreichtum auf allen trophischen Ebenen, wobei die Bedeutung der Nahrungsressourcen auf den höheren trophischen Ebenen der natürlichen Antagonisten zunahm. Die Parasitierungsrate wurde sowohl durch die Temperatur als auch durch die trophische Ebene bestimmt, was darauf hindeutet, dass sich die relative Bedeutung der Bottom-up- und Top-down-Kräfte mit dem Klimawandel verschieben könnte. Kapitel 3 – Saisonale Schwankungen in der Ökologie von tropischen hohlraumnistenden Hautflüglern Natürliche Populationen schwanken mit der Verfügbarkeit von Ressourcen, dem Vorhandensein natürlicher Feinde und klimatischen Schwankungen. Die Saisonalität ist jedoch auf tropischen Bergen noch nicht gut untersucht. Wir untersuchten saisonale Muster in der Nestbauaktivität, funktionale Merkmale und ökologische Raten bei drei verschiedenen Insektengruppen in niedrigeren und höheren Höhenlagen. Insekten wurden mit Nisthilfen gefangen, die während eines Zeitraums von 17 Monaten, der drei Trocken- und drei Regenzeiten umfasste, monatlich überprüft wurden. Die Insekten wurden nach ihren funktionalen Gilden eingeteilt. Alle Gruppen zeigten eine starke Saisonalität im Nestbau, die in niedrigeren Lagen höher war und dort zwischen den Gruppen stärker synchronisiert war. Die Saisonalität im Nestbau von Raupen- und Spinnen- jagenden Wespen war mit saisonalen Klimaschwankungen verbunden, während sie bei Bienen stark von der Verfügbarkeit von Blüten abhing, genauso wie die Überlebensrate und das Geschlechterverhältnis der Bienen von der Blütenmenge abhing. Die Anpassung an die Saisonalität der Umwelt könnte bedeuten, dass weitere Veränderungen der saisonalen Klimaschwankungen durch den Klimawandel einen Einfluss auf die lebensgeschichtlichen Merkmale tropischer Bergarten haben könnten. Kapitel 4 – Kryptische Arten und versteckte ökologische Wechselwirkungen bei Schmalbienen entlang eines Höhengradienten Starke Umweltgradienten, wie sie an Berghängen auftreten, stellen für Arten eine Herausforderung dar. Versteckte Anpassungen oder Interaktionen wurden in diesem Zusammenhang selten berücksichtigt. Als Modellorganismen haben wir Bienen der Gattung Lasioglossum verwendet, da Lasioglossum die einzige Bienengattung ist, die über den gesamten Höhengradienten am Kilimandscharo weit verbreitet ist. Wir fragten, ob und wie (a) kutikuläre Kohlenwasserstoffe (CHC), die als Barriere gegen Austrocknung wirken, sich in ihrer Zusammensetzung und Kettenlänge entlang von Temperatur- und Feuchtigkeitsänderungen verändern; (b) Lasioglossum Bienen ihre Pollennahrung mit wechselnder Ressourcenverfügbarkeit ändern; (c) Änderungen von Darm-Mikrobiota mit Pollennahrung und Klimabedingungen und Änderungen von Oberflächen-Mikrobiota mit CHC und Klimabedingungen zusammen hängen, und ob die Veränderungen eher durch den Wechsel von Lasioglossum Arten entlang des Höhengradienten beeinflusst werden. Wir fanden physiologische Anpassungen an das Klima in CHC, sowie Veränderungen in der Zusammensetzung von Pollennahrung und Mikrobiota, die auch miteinander korrelierten. Diese Ergebnisse deuten darauf hin, dass komplexe Wechselwirkungen und Rückkopplungen zwischen abiotischen und biotischen Bedingungen die Artenzusammensetzung in einer Gemeinschaft bestimmen. Kapitel 5 – Allgemeine Diskussion Abiotische und biotische Faktoren förderten die Artenvielfalt, Eigenschaften und Wechselwirkungen von Arten und sie wirkten unterschiedlich, je nachdem, welche funktionelle Gruppe untersucht wurde und ob räumliche oder zeitliche Einheiten berücksichtigt worden sind. Es ist daher wahrscheinlich, dass im Lichte des globalen Wandels verschiedene Arten, Merkmale und Wechselwirkungen unterschiedlich betroffen sein werden. Darüber hinaus könnte eine zunehmende Landnutzungsintensität zusätzliche Auswirkungen oder Wechselwirkungen mit dem Klimawandel auf die Biodiversität haben, auch wenn die potenziellen Landnutzungseffekte am Kilimandscharo noch gering sind und bis jetzt die hohlraumnistenden Hautflüglern nicht beeinträchtigen. Weitere Studien sollten sich mit Nahrungsnetzwerken befassen, die empfindlichere Veränderungen aufzeigen könnten. Nisthilfen bieten dafür ein gutes Modellsystem, um die Auswirkungen des globalen Wandels auf mehreren trophischen Ebenen zu untersuchen, und können auch direkte Auswirkungen des Klimawandels auf ganze lebensgeschichtliche Merkmale aufzeigen, wenn sie unter verschiedenen mikroklimatischen Bedingungen etabliert werden. Die nicht einheitlichen Auswirkungen abiotischer und biotischer Bedingungen auf mehrere Aspekte der Biodiversität, die in dieser Studie gezeigt wurden, zeigen auch, dass die Untersuchung verschiedener Aspekte der Biodiversität ein umfassenderes Bild vermitteln kann als Einzelbetrachtungen. KW - land use KW - Landnutzung KW - climate change KW - bees KW - wasps KW - biodiversity KW - Klimawandel KW - Bienen KW - Wespen KW - Biodiversität Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-182922 ER - TY - JOUR A1 - Stein, Katharina A1 - Coulibaly, Drissa A1 - Balima, Larba Hubert A1 - Goetze, Dethardt A1 - Linsenmair, Karl Eduard A1 - Porembski, Stefan A1 - Stenchly, Kathrin A1 - Theodorou, Panagiotis T1 - Plant-pollinator networks in savannas of Burkina Faso, West Africa JF - Diversity N2 - West African savannas are severely threatened with intensified land use and increasing degradation. Bees are important for terrestrial biodiversity as they provide native plant species with pollination services. However, little information is available regarding their mutualistic interactions with woody plant species. In the first network study from sub-Saharan West Africa, we investigated the effects of land-use intensity and climatic seasonality on plant–bee communities and their interaction networks. In total, we recorded 5686 interactions between 53 flowering woody plant species and 100 bee species. Bee-species richness and the number of interactions were higher in the low compared to medium and high land-use intensity sites. Bee- and plant-species richness and the number of interactions were higher in the dry compared to the rainy season. Plant–bee visitation networks were not strongly affected by land-use intensity; however, climatic seasonality had a strong effect on network architecture. Null-model corrected connectance and nestedness were higher in the dry compared to the rainy season. In addition, network specialization and null-model corrected modularity were lower in the dry compared to the rainy season. Our results suggest that in our study region, seasonal effects on mutualistic network architecture are more pronounced compared to land-use change effects. Nonetheless, the decrease in bee-species richness and the number of plant–bee interactions with an increase in land-use intensity highlights the importance of savanna conservation for maintaining bee diversity and the concomitant provision of ecosystem services. KW - bees KW - community composition KW - connectance KW - land-use intensity KW - modularity KW - mutualism KW - number of interactions KW - seasonality KW - woody plant richness Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-220157 SN - 1424-2818 VL - 13 IS - 1 ER - TY - JOUR A1 - Mayr, Antonia V. A1 - Peters, Marcell K. A1 - Eardley, Connal D. A1 - Renner, Marion E. A1 - Röder, Juliane A1 - Steffan-Dewenter, Ingolf T1 - Climate and food resources shape species richness and trophic interactions of cavity-nesting Hymenoptera JF - Journal of Biogeography N2 - Aim: Temperature, food resources and top‐down regulation by antagonists are considered as major drivers of insect diversity, but their relative importance is poorly understood. Here, we used cavity‐nesting communities of bees, wasps and their antagonists to reveal the role of temperature, food resources, parasitism rate and land use as drivers of species richness at different trophic levels along a broad elevational gradient. Location: Mt. Kilimanjaro, Tanzania. Taxon: Cavity‐nesting Hymenoptera (Hymenoptera: Apidae, Colletidae, Megachilidae, Crabronidae, Sphecidae, Pompilidae, Vespidae). Methods: We established trap nests on 25 study sites that were distributed over similar large distances in terms of elevation along an elevational gradient from 866 to 1788 m a.s.l., including both natural and disturbed habitats. We quantified species richness and abundance of bees, wasps and antagonists, parasitism rates and flower or arthropod food resources. Data were analysed with generalized linear models within a multi‐model inference framework. Results: Elevational species richness patterns changed with trophic level from monotonically declining richness of bees to increasingly humped‐shaped patterns for caterpillar‐hunting wasps, spider‐hunting wasps and antagonists. Parasitism rates generally declined with elevation but were higher for wasps than for bees. Temperature was the most important predictor of both bee and wasp host richness patterns. Antagonist richness patterns were also well predicted by temperature, but in contrast to host richness patterns, additionally by resource abundance and diversity. The conversion of natural habitats through anthropogenic land use, which included biomass removal, agricultural inputs, vegetation structure and percentage of surrounding agricultural habitats, had no significant effects on bee and wasp communities. Main conclusions: Our study underpins the importance of temperature as a main driver of diversity gradients in ectothermic organisms and reveals the increasingly important role of food resources at higher trophic levels. Higher parasitism rates at higher trophic levels and at higher temperatures indicated that the relative importance of bottom‐up and top‐down drivers of species richness change across trophic levels and may respond differently to future climate change. KW - land-use change KW - species richness KW - trophic levels KW - wasps KW - feeding guilds KW - antagonists KW - bees KW - bottom‐up and top‐down control KW - elevational gradients Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-208101 VL - 47 IS - 4 ER - TY - JOUR A1 - Ruedenauer, Fabian A. A1 - Wöhrle, Christine A1 - Spaethe, Johannes A1 - Leonhardt, Sara D. T1 - Do honeybees (Apis mellifera) differentiate between different pollen types? JF - PLoS ONE N2 - Bees receive nectar and pollen as reward for pollinating plants. Pollen of different plant species varies widely in nutritional composition. In order to select pollen of appropriate nutritional quality, bees would benefit if they could distinguish different pollen types. Whether they rely on visual, olfactory and/or chemotactile cues to distinguish between different pollen types, has however been little studied. In this study, we examined whether and how Apis mellifera workers differentiate between almond and apple pollen. We used differential proboscis extension response conditioning with olfactory and chemotactile stimulation, in light and darkness, and in summer and winter bees. We found that honeybees were only able to differentiate between different pollen types, when they could use both chemotactile and olfactory cues. Visual cues further improved learning performance. Summer bees learned faster than winter bees. Our results thus highlight the importance of multisensory information for pollen discrimination. KW - pollen KW - bees KW - honey bees KW - conditioned response KW - behavioral conditioning KW - foraging KW - nutrients KW - sensory cues Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-177537 VL - 13 IS - 11 ER - TY - JOUR A1 - Stein, Katharina A1 - Coulibaly, Drissa A1 - Stenchly, Kathrin A1 - Goetze, Dethardt A1 - Porembski, Stefan A1 - Lindner, André A1 - Konaté, Souleymane A1 - Linsenmair, Eduard K. T1 - Bee pollination increases yield quantity and quality of cash crops in Burkina Faso, West Africa JF - Scientific Reports N2 - Mutualistic biotic interactions as among flowering plants and their animal pollinators are a key component of biodiversity. Pollination, especially by insects, is a key element in ecosystem functioning, and hence constitutes an ecosystem service of global importance. Not only sexual reproduction of plants is ensured, but also yields are stabilized and genetic variability of crops is maintained, counteracting inbreeding depression and facilitating system resilience. While experiencing rapid environmental change, there is an increased demand for food and income security, especially in sub-Saharan communities, which are highly dependent on small scale agriculture. By combining exclusion experiments, pollinator surveys and field manipulations, this study for the first time quantifies the contribution of bee pollinators to smallholders’ production of the major cash crops, cotton and sesame, in Burkina Faso. Pollination by honeybees and wild bees significantly increased yield quantity and quality on average up to 62%, while exclusion of pollinators caused an average yield gap of 37% in cotton and 59% in sesame. Self-pollination revealed inbreeding depression effects on fruit set and low germination rates in the F1-generation. Our results highlight potential negative consequences of any pollinator decline, provoking risks to agriculture and compromising crop yields in sub-Saharan West Africa. KW - bees KW - pollination KW - Burkina Faso KW - cash crops KW - cotton KW - sesame Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-169914 VL - 7 IS - 17691 ER - TY - JOUR A1 - Sommerlandt, Frank M. J. A1 - Spaethe, Johannes A1 - Rössler, Wolfgang A1 - Dyer, Adrian G. T1 - Does Fine Color Discrimination Learning in Free-Flying Honeybees Change Mushroom-Body Calyx Neuroarchitecture? JF - PLoS One N2 - Honeybees learn color information of rewarding flowers and recall these memories in future decisions. For fine color discrimination, bees require differential conditioning with a concurrent presentation of target and distractor stimuli to form a long-term memory. Here we investigated whether the long-term storage of color information shapes the neural network of microglomeruli in the mushroom body calyces and if this depends on the type of conditioning. Free-flying honeybees were individually trained to a pair of perceptually similar colors in either absolute conditioning towards one of the colors or in differential conditioning with both colors. Subsequently, bees of either conditioning groups were tested in non-rewarded discrimination tests with the two colors. Only bees trained with differential conditioning preferred the previously learned color, whereas bees of the absolute conditioning group, and a stimuli-naïve group, chose randomly among color stimuli. All bees were then kept individually for three days in the dark to allow for complete long-term memory formation. Whole-mount immunostaining was subsequently used to quantify variation of microglomeruli number and density in the mushroom-body lip and collar. We found no significant differences among groups in neuropil volumes and total microglomeruli numbers, but learning performance was negatively correlated with microglomeruli density in the absolute conditioning group. Based on these findings we aim to promote future research approaches combining behaviorally relevant color learning tests in honeybees under free-flight conditions with neuroimaging analysis; we also discuss possible limitations of this approach.q KW - bees KW - behavioral conditioning KW - learning KW - color vision KW - vision KW - calyx KW - cognition KW - honey bees Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-147932 VL - 11 IS - 10 ER - TY - JOUR A1 - Lichtenstein, Leonie A1 - Sommerlandt, Frank M. J. A1 - Spaethe, Johannes T1 - Dumb and Lazy? A Comparison of Color Learning and Memory Retrieval in Drones and Workers of the Buff-Tailed Bumblebee, Bombus terrestris, by Means of PER Conditioning JF - PLoS One N2 - More than 100 years ago, Karl von Frisch showed that honeybee workers learn and discriminate colors. Since then, many studies confirmed the color learning capabilities of females from various hymenopteran species. Yet, little is known about visual learning and memory in males despite the fact that in most bee species males must take care of their own needs and must find rewarding flowers to obtain food. Here we used the proboscis extension response (PER) paradigm to study the color learning capacities of workers and drones of the bumblebee, Bombus terrestris. Light stimuli were paired with sucrose reward delivered to the insects’ antennae and inducing a reflexive extension of the proboscis. We evaluated color learning (i.e. conditioned PER to color stimuli) in absolute and differential conditioning protocols and mid-term memory retention was measured two hours after conditioning. Different monochromatic light stimuli in combination with neutral density filters were used to ensure that the bumblebees could only use chromatic and not achromatic (e.g. brightness) information. Furthermore, we tested if bees were able to transfer the learned information from the PER conditioning to a novel discrimination task in a Y-maze. Both workers and drones were capable of learning and discriminating between monochromatic light stimuli and retrieved the learned stimulus after two hours. Drones performed as well as workers during conditioning and in the memory test, but failed in the transfer test in contrast to workers. Our data clearly show that bumblebees can learn to associate a color stimulus with a sugar reward in PER conditioning and that both workers and drones reach similar acquisition and mid-term retention performances. Additionally, we provide evidence that only workers transfer the learned information from a Pavlovian to an operant situation. KW - memory KW - bumblebees KW - behavioral conditioning KW - honey bees KW - flowers KW - sucrose KW - bees KW - learning Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-125832 VL - 10 IS - 7 ER - TY - JOUR A1 - Stejskal, Kerstin A1 - Streinzer, Martin A1 - Dyer, Adrian A1 - Paulus, Hannes F. A1 - Spaethe, Johannes T1 - Functional Significance of Labellum Pattern Variation in a Sexually Deceptive Orchid (Ophrys heldreichii): Evidence of Individual Signature Learning Effects JF - PLoS One N2 - Mimicking female insects to attract male pollinators is an important strategy in sexually deceptive orchids of the genus Ophrys, and some species possess flowers with conspicuous labellum patterns. The function of the variation of the patterns remains unresolved, with suggestions that these enhance pollinator communication. We investigated the possible function of the labellum pattern in Ophrys heldreichii, an orchid species in which the conspicuous and complex labellum pattern contrasts with a dark background. The orchid is pollinated exclusively by males of the solitary bee, Eucera berlandi. Comparisons of labellum patterns revealed that patterns within inflorescences are more similar than those of other conspecific plants. Field observations showed that the males approach at a great speed and directly land on flowers, but after an unsuccessful copulation attempt, bees hover close and visually scan the labellum pattern for up to a minute. Learning experiments conducted with honeybees as an accessible model of bee vision demonstrated that labellum patterns of different plants can be reliably learnt; in contrast, patterns of flowers from the same inflorescence could not be discriminated. These results support the hypothesis that variable labellum patterns in O. heldreichii are involved in flower-pollinator communication which would likely help these plants to avoid geitonogamy. KW - nectar KW - color discrimination KW - bees KW - vision KW - evolution KW - pollination KW - guides KW - honeybee KW - apis mellifera KW - insects KW - signals KW - recognize images Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-137582 VL - 10 IS - 11 ER - TY - JOUR A1 - Pamir, Evren A1 - Szyszka, Paul A1 - Scheiner, Ricarda A1 - Nawrot, Martin P. T1 - Rapid learning dynamics in individual honeybees during classical conditioning JF - Frontiers in Behavioral Neuroscience N2 - Associative learning in insects has been studied extensively by a multitude of classical conditioning protocols. However, so far little emphasis has been put on the dynamics of learning in individuals. The honeybee is a well-established animal model for learning and memory. We here studied associative learning as expressed in individual behavior based on a large collection of data on olfactory classical conditioning (25 datasets, 3298 animals). We show that the group-averaged learning curve and memory retention score confound three attributes of individual learning: the ability or inability to learn a given task, the generally fast acquisition of a conditioned response (CR) in learners, and the high stability of the CR during consecutive training and memory retention trials. We reassessed the prevailing view that more training results in better memory performance and found that 24 h memory retention can be indistinguishable after single-trial and multiple-trial conditioning in individuals. We explain how inter-individual differences in learning can be accommodated within the Rescorla Wagner theory of associative learning. In both data-analysis and modeling we demonstrate how the conflict between population-level and single-animal perspectives on learning and memory can be disentangled. KW - sucrose sensitivity KW - sucrose responsiveness KW - learning curve KW - bees KW - apis mellifera KW - single-trial learning KW - classical conditioning KW - Rescorla-Wagner model KW - proboscis extension response (PER) Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-115365 SN - 1662-5153 VL - 8 IS - 313 ER -