Importance of olfactory and visuel cues of Echium for host-plant finding of the oligolectic bee Osmia adunca (Megachilidae)

Solitary bees are important pollinators of flowers. Besides nectar they collect pollen at flowers mainly to provide their larvae with food. Many bee species collect pollen only on a few closely related plant species (oligolecty) (Müller & al. 1997). Little is known about the visual and olfactorial signals they use for host-plant finding (Wcislo & Cane 1996). However, bees can olfactorily distinguish between different pollen species (von Frisch 1923), and a species-specific chemistry of pollen odour is known for some plant species (Bergström & al. 1995, Dobson & al. 1999). Further, it was shown that naïve oligolectic bees recognize their host-plant on the basis pollen volatiles (Dobson & Bergström 2000) and that flower-experienced bees could use pollen odours to assess pollen availability (Dobson & al. 1999). Besides scent, also visual cues are of relevance for host-plant finding, and bees orientate especially spectral contrasts. Biotests with dummy flowers revealed that colour contrast and not intensity and dominant wavelengths are influencing innate behavioural responses (Lunau 1990). Further it was shown that naïve bumblebees were most motivated to land on a flower when visual stimuli from the antheres are combined with olfactorial stimuli from the pollen (1992). We choose Osmia adunca P., which is highly specialized on Echium L., as a model to investigate the importance of floral cues for an oligolectic bee. Because bees learn to associate odours with reward more rapidly than visual cues (Menzel 1985), we hypothesize that scent plays a major role in attraction flower-experienced O. adunca females. We used gas chromatography to compare the scent of three Echium species with the scent of a closely related Anchusa species, and a spectrometer to compare the colour of the three Echium species. Additionally we conducted a biotest to determine the importance of visual and olfactorial signals of Echium for host-plant finding of experienced O. adunca females.Bienen besuchen Blüten, um u. a. Pollen zu sammeln, der hauptsächlich der Versorgung der Larven dient. Einige Bienenarten sammeln Pollen von nur einer oder wenigen Pflanzengattungen und werden als Oligolekten bezeichnet. Der Anlockung von Bienen dienen olfaktorische und visuelle Blütensignale. Wir postulierten, dass die eng auf Echium (Boraginaceae) spezialisierte Mauerbiene Osmia adunca (Hymenoptera: Megachilidae) gattungsspezifische visuelle und olfaktorische Blütensignale benutzt, um ihre Wirtspflanzen zu finden erkennen. Mittels chemischer Analysen (GC) konnten wir einen Echium-spezifischen Duft nachweisen, der sich deutlich von einer nah verwandten Anchusa Art unterscheidet. Biotests in einem Flugkäfig mit blütenerfahrenen, nestbauenden Weibchen ergaben weiterhin, dass Echium-Blütenduft bei der Erkennung der Pflanzen im Nahbereich eine große Rolle spielt, während visuelle Signale wahrscheinlich bei der Fernanlockung von Bedeutung sind. Die einem Reflexionsspektrometer analysierten visuellen Signale dreier Echium Arten ähnelten sehr und könnten daher vermutlich eine Funktion zur Anlockung von O. adunca haben. Weitere Tests müssen nun zeigen, welche Blütensignale naive Tiere für die Wirtspflanzenerkennung nutzen

Pollinator-attracting semiochemicals of the wasp-flower Epipactis helleborine

The orchid genus Epipactis is represented by 25 species in Europe (Richards 1982). Epipactis helleborine (L.) Crantz is the most common and widely distributed species of the genus (Wiefelspütz 1970), and is a prime example for wasp-flowers, because it is mainly pollinated by social wasps (Hymenoptera: Vespidae), like Vespula vulgaris and V. germanica (Müller 1873). Darwin (1888) already noticed that E. helleborine is almost exclusively ignored by bees and bumblebees, an observation that was confirmed in recent investigations (Keppert 2001). The flowers of E. helleborine show morphological, physiological and phenological adaptations to the visit and the pollination by Vespidae (Keppert 2001). They possess a reddish-brown or dirty purple coloration of the inflorescence (Keppert 2001), have relatively small, mostly bulbous blossoms with a broad entrance and bulbous widened, nectar-rich juice holders (Müller 1873, 1881; Schremmer 1962). Although there is much reported about wasp-pollinated flowers there is little known about the signals that are responsible for the attraction of wasps. Wiefelspütz (1970) proclaimed the statement that only the visual stimulus is responsible for the wasp attraction. Recently studies, however, assumed that odour is involved in the wasp attraction (Keppert 2001). Hölzler (2003) showed that the main attraction of the wasp-flower Epipactis for pollinators is its olfactory stimulus. It remains an unanswered question why E. helleborine flowers almost exclusively attracts social wasps, as opposed to bees and bumblebees. In this study we analysed the role of floral volatiles which are responsible for the specific attraction of social wasps. We supposed a mimicry-system in E. helleborine for the specific attraction of pollinators for the following reasons. So-called “green leaf volatiles” (GLVs) are emitted by plants while herbivorous insects, for example caterpillars, feed on them. GLVs thereby attract predators or parasitoids of the herbivorous insects (Dicke & Sabelis 1988; Turlings & al. 1990, 1995; Dicke & Vet 1999). Among the GLVs so far identified in former studies there are aldehydes, compounds that were also found in flower extracts of E. helleborine (Hölzler 2003). Therefore, we postulated that E. helleborine flowers produce GLVs in order to attract prey hunting social wasps for pollination. We performed bioassays and analysed flower odour gained to headspace-sampling using gas chromatography (GC), mass spectrometry (GC-MS) and gas chromatography coupled with electrophysiological analysis (GC-EAD) to investigate the hypothesis that E. helleborine flowers mimic “green leaf volatiles” (GLVs) to attract their pollinators.Die Orchideenart Epipactis helleborine gilt als typische Wespenblume. Die Blüten weisen Anpassungen an den Besuch und die Bestäubung durch soziale Faltenwespen (Hymenoptera: Vespidae) auf und werden häufig durch Vespula vulgaris und V. germanica bestäubt. In früheren Untersuchungen konnte gezeigt werden, dass olfaktorische Reize bei der Bestäuberanlockung eine übergeordnete Bedeutung vor optischen Reizen haben (Hölzler 2003). Die Frage, warum E. helleborine fast ausschließlich ihren optimalen Bestäuber, die soziale Faltenwespe, zur Bestäubung anlockt, und nicht auch auf andere Blütenbesucher attraktiv wirkt, ist noch unbeantwortet. Wir untersuchten die Hypothese, dass E. helleborine Blüten GLVs, die von Herbivoren befallenen Pflanzen abgegeben werden, nachahmen, um Beute jagende Wespen zur Bestäubung anzulocken. Dazu sammelten und analysierten wir Duftstoffe von Epipactis Blüten und mit Pieris-Raupen befallenen Kohl und identifizierten vier gemeinsam vorkommende GLVs. In Y-Rohrtests konnte die wespenanlockende Wirkung dieser Verbindungen nachgewiesen werden

The role of pollinator attracting scent in the sexually deceptive orchids Ophrys chestermanii, O. normanii and O. tenthredinifera

Sexual deception of male bees is one of the most remarkable mechanisms of pollination (Ackermann 1986, Proctor & al. 1996). Flowers of the orchid genus Ophrys mimic females of their pollinator species, usually bees and wasps, to attract males, which try to copulate with the flowers. During this so-called “pseudocopulation” the male removes the pollinia and transfers them to another flower to ensure pollination. Apart from visual and tactile cues, floral scent was shown to be most important for eliciting mating behaviour in males (Kullenberg 1961, Schiestl & al. 1999, Ayasse & al. 2003). Pollination in Ophrys is highly specific and usually each Ophrys species attracts only one pollinator species (Paulus & Gack 1990). The high degree of specialization provides the means of reproductive isolation between the intercrossable Ophrys-species (Ehrendorfer 1980). The complex odour-bouquets released by the flowers are species-specific and often consist of more than 100 different chemical compounds (Borg-Karlson & al. 1985, Ayasse 2006). Speciation in Ophrys-orchids may be brought about by changes in the pollinator attracting floral scent. The attraction of a new pollinator may act as a pre-zygotic isolation barrier (Stebbins 1970, Paulus & Gack 1990, Soliva & al. 2001). We investigated three sympatrically occuring Ophrys-species on Sardinia. O. chestermanii and O. normanii are endemic and are both pollinated by males of the bumblebee B. vestalis. O. tenthredinifera is pollinated by Eucera nigrilabris. There are different opinions concerning the taxonomic status of O. normanii. It has been described as an actual hybrid between O. chestermanii and O. tenthredinifera (Wood 1983). Paulus & Gack (1995) suggested that it is an own species, that either has developed from a hybrid between O. chestermanii and O. normanii or that has evolved by radiation from O. tenthredinifera. By conducting behavioural-tests with B. vestalis males, performing gas chromatographic analyses and electrophysiological studies we wanted to identify pollinator attracting scent and to clarify the taxonomic status of O. normanii.Sexualtäuschorchideen der Gattung Ophrys (Orchidaceae) imitieren die Weibchen ihrer Bestäuber in Duft, Form und Farbe. Insektenmännchen versuchen mit dem Labellum der Blüte zu kopulieren und transportieren den Pollen von Blüte zu Blüte, wodurch die Orchidee bestäubt wird. In dieser Arbeit untersuchten wir die Bestäuber anlockenden Duftstoffe der beiden endemisch auf Sardinien vorkommenden Arten O. normanii und O. chestermanii, die beide von Bombus vestalis Männchen (Hymenoptera: Apidae) bestäubt werden und von O. tenthredinifera, die Eucera nigrilabris (Hymenoptera: Apidae) zur Bestäubung anlockt. O. normanii wurde von Wood (1983) als Primärhybride beschrieben. Nach Paulus und Gack (1995) handelt es sich um eine hybridogene Art oder um eine Art die durch Abspaltung von O. tenthredinifera entstanden ist. Das Ziel der Untersuchungen war die Identifizierung Männchen-anlockender Verbindungen. Die Attraktivität der drei Arten für B. vestalis Männchen sollte Hinweise auf den Artstatus von O. normanii geben. In Biotests mit B. vestalis-Männchen lösten Blütenextrakte von O. normanii und O. chestermanii ebenso wie B. vestalis-Weibchen Kopulationsverhalten der Männchen aus, nicht jedoch Extrakte von O. tenthredinifera. Folglich handelt es sich bei O. normanii nicht um einen aktuellen Hybriden zwischen O. chestermanii und O. tenthredinifera. Ein Vergleich der GC-EAD-aktiven Duftbouquets mittels Diskriminanzanalyse ergab große Ähnlichkeiten zwischen O. normanii und O. chestermanii für die Substanzklassen der Ester, Alkohole und Fettsäuren, die daher vermutlich eine Schlüsselfunktion bei der Bestäuberanlockung haben

Macrocylic Di- and Tetranuclear Osmacycloferrocenophanes

The objective of this work is the synthesis of the novel di- and tetranuclear ortho-, meta-, and para-osmacycloferrocenophanes [h5-C5H4(CH2)nC6H4(CH2)nOs(CO)4(CH2)nC6H4(CH2)n-C5H4-h5]xFex (ortho, meta, para: n = 2, 4; meta, para: n = 3; x = 1, 2) consisting of an extended hydrocarbon skeleton, containing additionally 2 and 4 transition metal centers, respectively. Cyclophanes and metallocenophanes represent typical examples in supramolecular chemistry and are provided with several inherent features of general interest. Due to the steric requirement of transition metal fragments their introduction into the framework of cyclophanes and metallocenophanes affect the geometric parameters of the cavities. For the formation of the Os-C s bonds advantage of the bis(triflate) method has been taken, which is a variant of the cationic alkylation. This route was found to be the most straightforward and efficient way for the concomitant formation of several metal-carbon s bonds under very mild conditions. The triflate residue is an excellent and inert leaving group stabilizing carbenium-like carbon atoms at the ends of a hydrocarbon chain, thereby enabling an electrophilic attack of the terminal carbon atoms even at a weakly basic metal center. Prior to the application of the bis(triflate) method in this work several primary steps had to be elaborated. These investigations have been started with the synthesis of 1,n-bis(2-hydroxyethyl)benzene (n = 2-4), 1,n-bis(3-hydroxypropyl)benzene (n = 3, 4), and 1,n-bis(4-hydroxybutyl)benzene (n = 2-4). In each of these precursors one hydroxy group is substituted with bromine, the remaining OH-function is protected with tetrahydropyran. Subsequently bromine is substituted for cyclopentadienyl, and then the ferrocene derivative is generated with subsequent application of the bis(triflate) method. Additionally the redox potentials of the ferrocenediylalcohols and the dinuclear osmacycloferrocenophanes were investigated by cyclic voltammetry.Ziel dieser Arbeit ist die Synthese der neuartigen zwei- und vierkernigen ortho-, meta- und para-Osmacycloferrocenophane [h5-C5H4(CH2)nC6H4(CH2)nOs(CO)4(CH2)nC6H4(CH2)n-C5H4-h5]xFex (ortho, meta, para: n = 2, 4; meta, para: n = 3; x = 1, 2), die aus einem mit zwei bzw. vier zusätzlichen Übergangsmetallzentren ausgestatteten, ausgedehnten Kohlenwasserstoffgerüst bestehen. Cyclophane und Metallocenophane sind typische Vertreter aus dem Bereich der supramolekularen Chemie und mit Eigenschaften ausgestattet, die von allgemeinem Interesse sind. Aufgrund des sterischen Anspruchs der Übergangsmetallzentren beeinflussen sie das Grundgerüst der Cyclophane und Metallocenophane und damit die geometrischen Parameter der Kavitäten. Die Bis(triflat)-Methode, die eine Variante der kationischen Alkylierung darstellt, diente für die Bildung der Os-C-s-Bindung. Es handelt sich hierbei um den direktesten und besten Weg für die gleichzeitige Bildung mehrerer Metall-Kohlenstoff-s-Bindungen unter sehr schonenden Bedingungen. Der Triflat Rest ist eine hervorragende und inerte Abgangsruppe, der die Carbenium-artigen Kohlenstoffatome am Ende der Kohlenwasserstoffkette stabilisiert, wobei ein elektrophiler Angriff des endständigen Kohlenstoffatoms sogar an einem schwach basischen Metallzentrum ermöglicht wird. Vor Anwendung der die Bis(triflat) Methode mußten einige Ausgangsverbindungen hergestellt werden. Startverbindungen sind 1,n-Bis(2-hydroxyethyl)benzol (n = 2-4), 1,n-Bis(3-hydroxypropyl)benzol (n = 3, 4), and 1,n-Bis(4-hydroxybutyl)benzol (n = 2-4). In jeder dieser Verbindungen wird je eine OH-Funktion durch Brom ersetzt, die übrige Hydroxy-Gruppe wird mit THP geschützt. Anschließend wird das Brom durch Cyclopentadienyl substituiert und daraus dann das Ferrocen-Derivat generiert, mit darauf folgender Anwendung der Bis(triflat)-Methode. Schließlich wurden die Redoxpotentiale der Ferrocenalkohole und der zweikernigen Osmacycloferrocenophane durch Cyclovoltammetrie bestimmt

Temperature drives variation in flying insect biomass across a German malaise trap network

1. Among the many concerns for biodiversity in the Anthropocene, recent reports of flying insect loss are particularly alarming, given their importance as pollinators, pest control agents, and as a food source. Few insect monitoring programmes cover the large spatial scales required to provide more generalizable estimates of insect responses to global change drivers. 2. We ask how climate and surrounding habitat affect flying insect biomass using data from the first year of a new monitoring network at 84 locations across Germany comprising a spatial gradient of land cover types from protected to urban and crop areas. 3. Flying insect biomass increased linearly with temperature across Germany. However, the effect of temperature on flying insect biomass flipped to negative in the hot months of June and July when local temperatures most exceeded long-term averages. 4. Land cover explained little variation in insect biomass, but biomass was lowest in forests. Grasslands, pastures, and orchards harboured the highest insect biomass. The date of peak biomass was primarily driven by surrounding land cover, with grasslands especially having earlier insect biomass phenologies. 5. Standardised, large-scale monitoring provides key insights into the underlying processes of insect decline and is pivotal for the development of climate-adapted strategies to promote insect diversity. In a temperate climate region, we find that the positive effects of temperature on flying insect biomass diminish in a German summer at locations where temperatures most exceeded long-term averages. Our results highlight the importance of local adaptation in climate change-driven impacts on insect communities

Methane Mapping with Future Satellite Imaging Spectrometers

This study evaluates a new generation of satellite imaging spectrometers to measure point source methane emissions from anthropogenic sources. We used the Airborne Visible and Infrared Imaging Spectrometer Next Generation(AVIRIS-NG) images with known methane plumes to create two simulated satellite products. One simulation had a 30 m spatial resolution with similar to 200 Signal-to-Noise Ratio (SNR) in the Shortwave Infrared (SWIR) and the other had a 60 m spatial resolution with similar to 400 SNR in the SWIR; both products had a 7.5 nm spectral spacing. We applied a linear matched filter with a sparsity prior and an albedo correction to detect and quantify the methane emission in the original AVIRIS-NG images and in both satellite simulations. We also calculated an emission flux for all images. We found that all methane plumes were detectable in all satellite simulations. The flux calculations for the simulated satellite images correlated well with the calculated flux for the original AVIRIS-NG images. We also found that coarsening spatial resolution had the largest impact on the sensitivity of the results. These results suggest that methane detection and quantification of point sources will be possible with the next generation of satellite imaging spectrometers.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Two years of satellite-based carbon dioxide emission quantification at the world's largest coal-fired power plants

Carbon dioxide (CO2) emissions from combustion sources are uncertain in many places across the globe. Satellites have the ability to detect and quantify emissions from large CO2 point sources, including coal-fired power plants. In this study, we routinely made observations with the PRecursore IperSpettrale della Missione Applicativa (PRISMA) satellite imaging spectrometer and the Orbiting Carbon Observatory-3 (OCO-3) instrument aboard the International Space Station at over 30 coal-fired power plants between 2021 and 2022. CO2 plumes were detected in 50 % of the acquired PRISMA scenes, which is consistent with the combined influence of viewing parameters on detection (solar illumination and surface reflectance) and unknown factors (e.g., daily operational status). We compare satellite-derived emission rates to in situ stack emission observations and find average agreement to within 27 % for PRISMA and 30 % for OCO-3, although more observations are needed to robustly characterize the error. We highlight two examples of fusing PRISMA with OCO-2 and OCO-3 observations in South Africa and India. For India, we acquired PRISMA and OCO-3 observations on the same day and used the high-spatial-resolution capability of PRISMA (30 m spatial/pixel resolution) to partition relative contributions of two distinct emitting power plants to the net emission. Although an encouraging start, 2 years of observations from these satellites did not produce sufficient observations to estimate annual average emission rates within low (&lt;15 %) uncertainties. However, as the constellation of CO2-observing satellites is poised to significantly improve in the coming decade, this study offers an approach to leverage multiple observation platforms to better quantify and characterize uncertainty for large anthropogenic emission sources.</p