The plant’s flower practices a very special mimicry: It produces three chemical substances that are usually emitted as alarm pheromones among aphids. Hoverfly females smell the alarm and lay their eggs close to the aphids, which are the perfect baby food for their hatching larvae.
Eastern marsh helleborine (Epipactis veratrifolia), an orchid species, has successfully lured a hoverfly of the genus Ischiodon by mimicking alarm pheromones usually emitted by aphids. MPI Chemical Ecology, Johannes Stökl
By mimicking these alarm pheromones, the orchid takes advantage of the hoverfly females, deceiving them into pollinating its flower. The flies even lay their eggs on the flower. However, the hatching larvae are doomed, because no aphids are available in the orchid flower. (Proceedings of the Royal Society B, October 13, 2010)
Beautiful but cunning
Even Darwin was a self-admitted orchid lover. Dictionaries describe orchids as exotic ornamentals. Indeed, these plants – more than 30000 different species are thought to exist – are exotic due their extraordinary and diverse flower morphology. However, they are also exotic from a point of view other than beauty: as crafty imposters in order to achieve reproduction and to make sure that their ovaries are pollinated. Orchids depend on the assistance of pollinators, and like many other flowering plants, attract insects.
Epipactis veratrifolia, an orchid native in South Turkey, the Middle East, and Cyprus, has specialized in hoverflies. Because these insects prefer aphids as food for their larvae, the orchid produces three aphid alarm substances, α- and β-pinene, and β-myrcene and β-phellandrene, all of which attract hoverfly females. Interestingly, as the scientists observed, even male hoverflies hang around the orchids, hoping for a chance to copulate with the attracted females.
A bit of nectar as reward
“Hoverfly females as well as males enjoy the small amount of nectar the orchid flower provides. Both sexes serve as pollen transmitters,” says ecologist Johannes Stökl. The alarm substances lure five of the different hoverfly species that feed on aphids. Females lay all their eggs in the flower of the orchid, although no aphids are there. “We assume that the insects are not only deceived by the aphid alarm pheromones, but also fall for the aphid-like dark warts in the orchid’s flower,” explains Bill Hansson, director at the Max Planck Institute.
Mass spectra and electroantennograms
The aphid species Megoura viciae preferred by Episyrphus balteatus hoverflies produces α- and β-pinene as well as β-myrcene. These volatile substances generate measurable electrical impulses in the hoverfly antennae. Behavioral experiments carried out by the research team supported the assumption that it is exactly these substances that attract hoverflies and encourage oviposition. Further analyses revealed that the orchid Epipactis veratrifolia does not mimic the alarm pheromones of just one aphid species, because the volatiles emitted by the aphids and the flower differ in amount and constitution.
An evolutionary dead end?
Is Epipactis veratrifolia a ruthless imposter? Johannes Stökl answers: “At least the plant provides a small amount of nectar for the deceived hoverflies. This is comparable to two related species, the wasp-pollinated orchids E. helleborine and E. purpurata, which lure stingy insects by mimicking their prey, mostly butterfly larvae. However, unlike Epipactis veratrifolia these species reward their pollinators by providing large amounts of nectar.”
Nevertheless, the scientist would classify the Eastern marsh helleborine as a treacherous imposter, because hoverfly larvae hatching from the eggs laid in its flowers won’t find any food there and must die. From an evolutionary perspective this seems to be a contradiction: If hoverfly larvae die, the population of this species is decimated and as a consequence the number of pollinators decreases.
“We cannot provide a coherent explanation of this conflict. However, we can imagine where the mimicry of the alarm pheromone is originated,” says Bill Hansson. The plant is remarkably aphid-free, probably due to the emission of α- and β-pinine. These two volatiles are produced by aphids in case of danger. Therefore aphids avoid everything that smells of α- and β-pinine. Both substances may have originally been used by the Eastern marsh helleborine as a defense against aphids. Once hoverflies were fooled and mistook the volatiles for aphids, they also served the purpose of attracting pollinators. [JWK, AO]
Johannes Stökl, Jennifer Brodmann, Amots Dafni, Manfred Ayasse, Bill S. Hansson: Smells like aphids: orchid flowers mimic aphid alarm pheromones to attract hoverflies for pollination. Proceedings of the Royal Society B, Online, October 13, 2010, DOI: 10.1098/rspb.2010.1770
Prof. Dr. Bill S. Hansson, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, 07745 Jena, Germany, phone +49 (0)3641/57-1400, -1401; mobile: +49 (0)175 4308222; firstname.lastname@example.org
Dr. Johannes Stökl, Regensburg University, Universitätsstraße 31, 93053 Regensburg, Germany, phone. +49 (0)941 943 2155, mobile +49 (0)179 9430400, email@example.com
Angela Overmeyer, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, 07745 Jena, Germany. Tel.: +49 (0)3641- 57 2110; firstname.lastname@example.org
Dr. Jan-Wolfhard Kellmann | Max-Planck-Institut
Water forms 'spine of hydration' around DNA, group finds
26.05.2017 | Cornell University
How herpesviruses win the footrace against the immune system
26.05.2017 | Helmholtz-Zentrum für Infektionsforschung
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy