TY - JOUR A1 - Streinzer, Martin A1 - Chakravorty, Jharna A1 - Neumayer, Johann A1 - Megu, Karsing A1 - Narah, Jaya A1 - Schmitt, Thomas A1 - Bharti, Himender A1 - Spaethe, Johannes A1 - Brockmann, Axel T1 - Species composition and elevational distribution of bumble bees (Hymenoptera, Apidae, Bombus Latreille) in the East Himalaya, Arunachal Pradesh, India JF - ZooKeys N2 - The East Himalaya is one of the world’s most biodiverse ecosystems. However, very little is known about the abundance and distribution of many plant and animal taxa in this region. Bumble bees are a group of cold-adapted and high elevation insects that fulfil an important ecological and economical function as pollinators of wild and agricultural flowering plants and crops. The Himalayan mountain range provides ample suitable habitats for bumble bees. Systematic study of Himalayan bumble bees began a few decades ago and the main focus has centred on the western region, while the eastern part of the mountain range has received little attention and only a few species have been verified. During a three-year survey, more than 700 bumble bee specimens of 21 species were collected in Arunachal Pradesh, the largest of the north-eastern states of India. The material included a range of species that were previously known from a limited number of collected specimens, which highlights the unique character of the East Himalayan ecosystem. Our results are an important first step towards a future assessment of species distribution, threat, and conservation. Clear elevation patterns of species diversity were observed, which raise important questions about the functional adaptations that allow bumble bees to thrive in this particularly moist region in the East Himalaya. KW - Alpine habitats KW - Apidae KW - conservation KW - global change KW - insect collection KW - pollination Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-201937 VL - 851 ER - TY - JOUR A1 - Streinzer, Martin A1 - Brockmann, Axel A1 - Nagaraja, Narayanappa A1 - Spaethe, Johannes T1 - Sex and Caste-Specific Variation in Compound Eye Morphology of Five Honeybee Species JF - PLoS ONE N2 - Ranging from dwarfs to giants, the species of honeybees show remarkable differences in body size that have placed evolutionary constrains on the size of sensory organs and the brain. Colonies comprise three adult phenotypes, drones and two female castes, the reproductive queen and sterile workers. The phenotypes differ with respect to tasks and thus selection pressures which additionally constrain the shape of sensory systems. In a first step to explore the variability and interaction between species size-limitations and sex and caste-specific selection pressures in sensory and neural structures in honeybees, we compared eye size, ommatidia number and distribution of facet lens diameters in drones, queens and workers of five species (Apis andreniformis, A. florea, A. dorsata, A. mellifera, A. cerana). In these species, male and female eyes show a consistent sex-specific organization with respect to eye size and regional specialization of facet diameters. Drones possess distinctly enlarged eyes with large dorsal facets. Aside from these general patterns, we found signs of unique adaptations in eyes of A. florea and A. dorsata drones. In both species, drone eyes are disproportionately enlarged. In A. dorsata the increased eye size results from enlarged facets, a likely adaptation to crepuscular mating flights. In contrast, the relative enlargement of A. florea drone eyes results from an increase in ommatidia number, suggesting strong selection for high spatial resolution. Comparison of eye morphology and published mating flight times indicates a correlation between overall light sensitivity and species-specific mating flight times. The correlation suggests an important role of ambient light intensities in the regulation of species-specific mating flight times and the evolution of the visual system. Our study further deepens insights into visual adaptations within the genus Apis and opens up future perspectives for research to better understand the timing mechanisms and sensory physiology of mating related signals. KW - eyes KW - foraging KW - honey bees KW - insect flight KW - physiological parameters KW - sensory systems KW - vision KW - visual system Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-96412 ER - TY - THES A1 - Spaethe, Johannes T1 - Sensory Ecology of Foraging in Bumblebees T1 - Sensorische Ökologie bei Sammelnden Hummeln N2 - Pollinating insects exhibit a complex behavior while foraging for nectar and pollen. Many studies have focused on ultimate mechanisms of this behavior, however, the sensory-perceptual processes that constrain such behavior have rarely been considered. In the present study I used bumblebees (Bombus terrestris), an important pollinating insect, to investigate possible sensory constraints on foraging behavior. Additionally, I survey inter-individual variation in the sensory capabilities and behavior of bumblebees caused by the pronounced size polymorphism among members of a single colony. In the first chapter I have focused on the sensory-perceptual processes that constrain the search for flowers. I measured search time for artificial flowers of various sizes and colors, a key variable defining the value of a prey type in optimal foraging theory. When flowers were large, search times correlate well with the color contrast of the targets with their green foliage-type background, as predicted by a model of color opponent coding using inputs from the bee's UV, blue, and green receptors. Targets which made poor color contrast with their backdrop, such as white, UV-reflecting ones, or red flowers, take longest to detect, even though brightness contrast with the background is pronounced. When searching for small targets, bumblebees change their strategy in several ways. They fly significantly slower and closer to the ground, so increasing the minimum detectable area subtended by an object on the ground. In addition they use a different neuronal channel for flower detection: instead of color contrast, they now employ only the green receptor signal for detection. I related these findings to temporal and spatial limitations of different neuronal channels involved in stimulus detection and recognition. Bumblebees do not only possess species-specific sensory capacities but they also exhibit inter-individual differences due to size. Therefore, in the next two chapters I have examined size-related effects on the visual and olfactory system of Bombus terrestris. Chapter two deals with the effect of scaling on eye architecture and spatial resolving power of workers. Foraging efficiency in bees is strongly affected by proficiency of detecting flowers. Both floral display size and bee spatial vision limit flower detection. In chapter one I have shown that search times for flowers strongly increases with decreasing floral display size. The second factor, bee spatial vision, is mainly limited by two properties of compound eyes: (a) the interommatidial angle Çå and (b) the ommatidial acceptance angle Çá. When a pollinator strives to increase the resolving power of its eyes, it is forced to increase both features simultaneously. Bumblebees show a large variation in body size. I found that larger workers with larger eyes possess more ommatidia and larger facet diameters. Large workers with twice the size of small workers (thorax width) have about 50 per cent more ommatidia, and a 1.5 fold enlarged facet diameter. In a behavioral test, large and small workers were trained to detect the presence of a colored stimulus in a Y-maze apparatus. The stimulus was associated with a sucrose reward and was presented in one arm, the other arm contained neither stimulus nor reward. The minimum visual angle a bee is able to detect was estimated by testing the bee at different stimuli sizes subtending angles between 30° and 3° on the bee’s eye. Minimum visual detection angles range from 3.4° to 7.0° among tested workers. Larger bumblebees are able to detect objects subtending smaller visual angles, i.e. they are able to detect smaller objects than their small conspecifics. Thus morphological and behavioral findings indicate an improved visual system in larger bees. Beside vision, olfaction is the most important sensory modality while foraging in bees. Bumblebees utilize species-specific odors for detecting and identifying nectar and pollen rich flowers. In chapter three I have investigated the olfactory system of Bombus terrestris and the effect of scaling on antennal olfactory sensilla and the first olfactory neuropil in the bumblebee brain, the antennal lobes. I found that the pronounced size polymorphism exhibited by bumblebees also effects their olfactory system. Sensilla number (I measured the most common olfactory sensilla type, s. placodea), sensilla density, volume of antennal lobe neuropil and volume of single identified glomeruli correlate significantly with worker’s size. The enlarged volume of the first olfactory neuropil in large individuals is caused by an increase in glomeruli volume and coarse neuropil volume. Additionally, beside an overall increase of brain volume with scaling I found that the olfactory neuropil increases disproportionately compared to a higher order neuropil, the central body. The data predict a higher odor sensitivity in larger bumblebee workers. In the last chapter I have addressed the question if scaling alters foraging behavior and rate in freely foraging bumblebees. I observed two freely foraging B. terrestris colonies and measured i) trip number, ii) trip time, iii) proportion of nectar trips, and iv) nectar foraging rate of different sized foragers. In all observation periods large foragers exhibit a significantly higher foraging rate than small foragers. None of the other three foraging parameters is affected by workers’ size. Thus, large foragers contribute disproportionately more to the current nectar influx of their colony. To summarize, this study shows that understanding the mechanisms of visual information processing and additionally comprising inter-individual differences of sensory capabilities is crucial to interpret foraging behavior of bees. N2 - Blüten bestäubende Insekten zeigen während ihrer Suche nach Nektar und Pollen ein komplexes Sammelverhalten. Bisher wurde eine Vielzahl von Studien durchgeführt um die ultimaten Mechanismen dieses Verhaltens aufzuklären; jedoch die diesem Verhalten zugrundeliegenden sensorischen Leistungen und Limitierungen wurden dabei nur selten berücksichtigt. In der vorliegenden Arbeit habe ich das Sammelverhalten von Hummeln (Bombus terrestris) und potentielle, das Verhalten limitierende sensorischen Zwänge untersucht. Zusätzlich konnte ich Unterschiede im sensorischen System individueller Hummeln aufdecken, die durch den ausgeprägten Größenpolymorphismus dieser Tiere verursacht werden. Im ersten Kapitel habe ich die visuellen Prozesse, die die Suche nach Blüten limitieren betrachtet. Hierfür habe ich die Suchzeiten von Hummeln für künstliche Blüten verschiedener Größe und Farbe in einer Flugarena bestimmt. Bei großen Blüten korrelieren die gemessenen Suchzeiten mit dem Farbkontrast zwischen der Blüte und dem blatt-grünen Hintergrund. Bei Blüten mit geringem Farbkontrast benötigen die Tiere am längsten um sie zu detektieren, obwohl die Blüten einen starken Helligkeitskontrast aufweisen. Diese Ergebnisse stimmen mit den Vorhersagen eines Farbseh-Modells überein, das die Information von den UV-, Blau- und Grünrezeptoren der Hummel verrechnet. Bei der Suche nach kleinen Blüten allerdings ändern die Hummeln ihre Strategie. Sie fliegen jetzt signifikant langsamer und näher am Untergrund um dadurch die Wahrscheinlichkeit zu erhöhen, die Blüten zu detektieren. Zusätzlich benutzen die Hummeln einen anderen neuronalen Kanal für die Blütenerkennung: anstatt des Farbkontrastes nutzen sie jetzt nur noch die Informationen des Grünrezeptors, d.h. den Kontrast zwischen Blüte und Hintergrund, der durch den Grünrezeptor wahrgenommen wird. Ich konnte zeigen, dass der Wechsel zwischen den beiden neuronalen Kanälen durch zeitliche und räumliche Eigenschaften dieser Kanäle verursacht wird. Die sensorischen Leistungen einer Hummel sind nicht nur durch ihre Artzugehörigkeit festgelegt, sondern weisen beträchtliche Unterschiede zwischen großen und kleinen Tieren auf. In den nächsten zwei Kapiteln habe ich deshalb Größeneffekte auf das visuelle und olfaktorische System von Bombus terrestris untersucht. Im zweiten Kapitel beschäftige ich mich mit den Auswirkungen des Größenpolymorphismus auf die Augenmorphologie und das räumliche Auflösungsvermögen von Hummelarbeiterinnen. Das räumliche Auflösungsvermögen des Hummelauges wird hauptsächlich von zwei Faktoren bestimmt: (a) dem Divergenzwinkel zwischen zwei Ommatidienachsen Çå, und (b) dem Öffnungswinkel eines Ommatidiums Çá. Beide Faktoren sind von der Zahl und dem Durchmesser der vorhandenen Ommatidien in einem Komplexauge beeinflußt. Ich konnte nachweisen, daß sich große und kleine Hummeln stark in der Zahl und dem Durchmesser ihrer Ommatidien unterscheiden. Große Hummeln mit der doppelten Thoraxbreite im Vergleich zu ihren kleinen Nestgenossinnen weisen 50 Prozent mehr Ommatidien und einen 1.5-fachen Linsendurchmesser auf. In einem Verhaltensversuch habe ich den kleinsten Sehwinkel, mit dem ein farbiges Objekt von einer Hummel noch erkannt werden kann bestimmt. Auch hier zeigte sich ein starker Größeneffekt. Um so größer die Hummel ist, um so kleiner ist der Sehwinkel unter dem sie ein Objekt gerade noch wahrnehmen kann. Sowohl morphologische Daten als auch Verhaltensdaten zeigen deutlich, dass größere Hummeln ein besseres visuelles System besitzen. Neben dem Sehen ist der Duft die wichtigste sensorische Modalität, die Hummeln während des Sammelns nutzen. Im nächsten Kapitel habe ich mich daher mit möglichen Größeneffekten auf das olfaktorische System beschäftigt. Ich konnte zeigen, daß die Zahl der wichtigsten olfaktorischen Sensillen auf der Antenne, Sensilla placodea, mit zunehmender Körpergröße ansteigt. Das erste olfaktorische Neuropil im Gehirn, die Antennalloben, skalieren ebenfalls mit der Körpergröße. Die Volumenzunahme des Neuropils ist auf eine Volumenzunahme der einzelnen Glomeruli und der Zahl der Interneurone zurückzuführen. Außerdem konnte ich nachweisen, daß das Volumen des olfaktorische Neuropils im Vergleich zu zentralen Hirnregionen überproportional zunimmt. Die Ergebnisse lassen eine höhere Sensitivität des olfaktorischen Systems bei großen Hummeln erwarten. Im letzten Kapitel habe ich mögliche Auswirkung der Körpergröße auf das Sammelverhalten von Hummeln unter natürlichen Bedingungen untersucht. Ein überlegenes visuelles und olfaktorisches System bei größeren Hummeln läßt eine bessere Blütenerkennung, und damit auch eine höhere Sammeleffizienz vermuten. Hierfür habe ich Nektarsammelraten von verschieden großen Tieren im Freiland bestimmt. Größere Tiere zeigen dabei eine höhere Sammelrate (Nektareintrag pro Zeit) im Vergleich zu ihren kleineren Nestgenossinnen. Größere Tiere tragen damit überproportional zum täglichen Nektarinflux einer Kolonie bei. Die Ergebnisse dieser Arbeit zeigen deutlich, dass das Sammelverhalten bei Blüten besuchenden Insekten nur dann richtig verstanden und interpretiert werden kann, wenn man die dem Sammeln zugrundeliegenden sensorischen Prozesse und mögliche individuelle Modifikationen kennt und mit einbezieht. KW - Hummeln KW - Nahrungserwerb KW - Wahrnehmung KW - Hummel KW - Bombus terrestris KW - Sammelverhalten KW - Farbsehen KW - Olfaktorik KW - Größenvariation KW - Arbeitsteilung KW - Bumblebees KW - Bombus terrestris KW - Foraging KW - Behavior KW - Color Vision KW - Olfaction KW - Scaling KW - Division of Labor Y1 - 2001 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-1179692 ER - TY - JOUR A1 - Albert, Štefan A1 - Spaethe, Johannes A1 - Grübel, Kornelia A1 - Rössler, Wolfgang T1 - Royal jelly-like protein localization reveals differences in hypopharyngeal glands buildup and conserved expression pattern in brains of bumblebees and honeybees N2 - Royal jelly proteins (MRJPs) of the honeybee bear several open questions. One of them is their expression in tissues other than the hypopharyngeal glands (HGs), the site of royal jelly production. The sole MRJP-like gene of the bumblebee, Bombus terrestris (BtRJPL), represents a pre-diversification stage of the MRJP gene evolution in bees. Here we investigate the expression of BtRJPL in the HGs and the brain of bumblebees. Comparison of the HGs of bumblebees and honeybees revealed striking differences in their morphology with respect to sex- and caste-specific appearance, number of cells per acinus, and filamentous actin (F-actin) rings. At the cellular level, we found a temporary F-actin-covered meshwork in the secretory cells, which suggests a role for actin in the biogenesis of the end apparatus in HGs. Using immunohistochemical localization, we show that BtRJPL is expressed in the bumblebee brain, predominantly in the Kenyon cells of the mushroom bodies, the site of sensory integration in insects, and in the optic lobes. Our data suggest that a dual glandbrain function preceded the multiplication of MRJPs in the honeybee lineage. In the course of the honeybee evolution, HGs dramatically changed their morphology in order to serve a food-producing function. KW - Hypopharyngeal glands KW - Bumblebee KW - Bombus KW - Brain KW - Labial glands KW - Immunohistochemistry KW - Kenyon cells KW - Mushroom bodies KW - Honeybee Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-112733 ER - TY - JOUR A1 - Rössler, Wolfgang A1 - Spaethe, Johannes A1 - Groh, Claudia T1 - Pitfalls of using confocal-microscopy based automated quantification of synaptic complexes in honeybee mushroom bodies (response to Peng and Yang 2016) JF - Scientific Reports N2 - A recent study by Peng and Yang in Scientific Reports using confocal-microscopy based automated quantification of anti-synapsin labeled microglomeruli in the mushroom bodies of honeybee brains reports potentially incorrect numbers of microglomerular densities. Whereas several previous studies using visually supervised or automated counts from confocal images and analyses of serial 3D electron-microscopy data reported consistent numbers of synaptic complexes per volume, Peng and Yang revealed extremely low numbers differing by a factor of 18 or more from those obtained in visually supervised counts, and by a factor 22–180 from numbers in two other studies using automated counts. This extreme discrepancy is especially disturbing as close comparison of raw confocal images of anti-synapsin labeled whole-mount brain preparations are highly similar across these studies. We conclude that these discrepancies may reside in potential misapplication of confocal imaging followed by erroneous use of automated image analysis software. Consequently, the reported microglomerular densities during maturation and after manipulation by insecticides require validation by application of appropriate confocal imaging methods and analyses tools that rely on skilled observers. We suggest several improvements towards more reliable or standardized automated or semi-automated synapse counts in whole mount preparations of insect brains. KW - confocal-microscopy based automated quantification KW - mushroom bodies KW - honeybees KW - brain Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170451 VL - 7 IS - 9786 ER - TY - JOUR A1 - Lichtenstein, Leonie A1 - Grübel, Kornelia A1 - Spaethe, Johannes T1 - Opsin expression patterns coincide with photoreceptor development during pupal development in the honey bee, Apis mellifera JF - BMC Developmental Biology N2 - Background: The compound eyes of insects allow them to catch photons and convert the energy into electric signals. All compound eyes consist of numerous ommatidia, each comprising a fixed number of photoreceptors. Different ommatidial types are characterized by a specific set of photoreceptors differing in spectral sensitivity. In honey bees, males and females possess different ommatidial types forming distinct retinal mosaics. However, data are lacking on retinal ontogeny and the mechanisms by which the eyes are patterned. In this study, we investigated the intrinsic temporal and circadian expression patterns of the opsins that give rise to the ultraviolet, blue and green sensitive photoreceptors, as well as the morphological maturation of the retina during pupal development of honey bees. Results: qPCR and histological labeling revealed that temporal opsin mRNA expression differs between sexes and correlates with rhabdom elongation during photoreceptor development. In the first half of the pupal stage, when the rhabdoms of the photoreceptors are still short, worker and (dorsal) drone retinae exhibit similar expression patterns with relatively high levels of UV (UVop) and only marginal levels of blue (BLop) and green (Lop1) opsin mRNA. In the second half of pupation, when photoreceptors and rhabdoms elongate, opsin expression in workers becomes dominated by Lop1 mRNA. In contrast, the dorsal drone eye shows high expression levels of UVop and BLop mRNA, whereas Lop1 mRNA level decreases. Interestingly, opsin expression levels increase up to 22-fold during early adult life. We also found evidence that opsin expression in adult bees is under the control of the endogenous clock. Conclusions: Our data indicate that the formation of the sex-specific retinal composition of photoreceptors takes place during the second half of the pupal development, and that opsin mRNA expression levels continue to increase in young bees, which stands in contrast to Drosophila, where the highest expression levels are found during the late pupal stage and remain constant in adults. From an evolutionary perspective, we hypothesize that the delayed retinal maturation during the early adult phase is linked to the delayed transition from indoor to outdoor activities in bees, when vision becomes important. KW - insect vision KW - photoreceptor KW - spectral sensitivity KW - visual pigments KW - behavioral transition Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-175665 VL - 18 IS - 1 ER - TY - JOUR A1 - Leonhardt, Sara D. A1 - Lihoreau, Mathieu A1 - Spaethe, Johannes T1 - Mechanisms of nutritional resource exploitation by insects JF - Insects N2 - Insects have evolved an extraordinary range of nutritional adaptations to exploit other animals, plants, bacteria, fungi and soils as resources in terrestrial and aquatic environments. This special issue provides some new insights into the mechanisms underlying these adaptations. Contributions comprise lab and field studies investigating the chemical, physiological, cognitive and behavioral mechanisms that enable resource exploitation and nutrient intake regulation in insects. The collection of papers highlights the need for more studies on the comparative sensory ecology, underlying nutritional quality assessment, cue perception and decision making to fully understand how insects adjust resource selection and exploitation in response to environmental heterogeneity and variability. KW - nutritional adaptations Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-211161 SN - 2075-4450 VL - 11 IS - 9 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 - 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 - Rakosy, Demetra A1 - Streinzer, Martin A1 - Paulus, Hannes F. A1 - Spaethe, Johannes T1 - Floral visual signal increases reproductive success in a sexually deceptive orchid JF - Arthropod-Plant Interactions N2 - Sexually deceptive orchids mimic signals emitted by female insects in order to attract mate-searching males. Specific attraction of the targeted pollinator is achieved by sex pheromone mimicry, which constitutes the major attraction channel. In close vicinity of the flower, visual signals may enhance attraction, as was shown recently in the sexually deceptive orchid Ophrys heldreichii. Here, we conducted an in situ manipulation experiment in two populations of O. heldreichii on Crete to investigate whether the presence/absence of the conspicuous pink perianth affects reproductive success in two natural orchid populations. We estimated reproductive success of three treatment groups (with intact, removed and artificial perianth) throughout the flowering period as pollinaria removal (male reproductive success) and massulae deposition (female reproductive success). Reproductive success was significantly increased by the presence of a strong visual signal—the conspicuous perianth—in one study population, however, not in the second, most likely due to the low pollinator abundance in the latter population. This study provides further evidence that the coloured perianth in O. heldreichii is adaptive and thus adds to the olfactory signal to maximise pollinator attraction and reproductive success. KW - sexual deception KW - eucera berlandi KW - male bees KW - ophrys heldreichii KW - pollination Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127209 VL - 6 IS - 4 ER -