Orchids mimic green-leaf volatiles to attract prey-hunting wasps for pollination.
An outstanding feature of orchids is the diversity of their pollination systems [1]. Most remarkable are those species that employ chemical deceit for the attraction of pollinators [2]. The orchid Epipactis helleborine is a typical wasp flower, exhibiting physiological and morphological adaptations for the attraction of pollinating social wasps [3]. As noted by Darwin [1], this species is almost entirely overlooked by other potential pollinators, despite a large nectar reward. Therefore, the mechanism for the attraction of pollinating social wasps was something of a mystery. By using a combination of behavioral experiments, electrophysiological investigations, and chemical analyses, we demonstrate for the first time that the flowers of E. helleborine and E. purpurata emit green-leaf volatiles (GLVs), which are attractive to foragers of the social wasps Vespula germanica and V. vulgaris. GLVs, emitted by damaged plant tissues, are known to guide parasitic wasps to their hosts [4]. Several E. helleborine GLVs that induced response in the antennae of wasps were also emitted by cabbage leaves infested with caterpillars (Pieris brassicae), which are common prey items for wasps [5]. This is the first example in which GLVs have been implicated in chemical mimicry for the attraction of pollinating insects.
Brodmann
Jennifer
J
Institute of Experimental Ecology, University of Ulm, 89069 Ulm, Germany.
Twele
Robert
R
Institute of Organic Chemistry, University of Hamburg, 20146 Hamburg, Germany.
Francke
Wittko
W
Institute of Organic Chemistry, University of Hamburg, 20146 Hamburg, Germany.
Hölzler
Gerald
G
Department of Evolutionary Biology, University of Vienna, 1090 Vienna, Austria.
Zhang
Qing-He
QH
Sterling International, Spokane, Washington 99216-1616.
Ayasse
Manfred
M
Institute of Experimental Ecology, University of Ulm, 89069 Ulm, Germany. Electronic address: manfred.ayasse@uni-ulm.de.
D000818:Animals; D001070:Appetitive Behavior / Q000502:physiology; D001937:Brassica / Q000378:metabolism / Q000469:parasitology; D035264:Flowers / Q000502:physiology*; D006790:Host-Parasite Interactions / Q000502:physiology; D007814:Larva / Q000469:parasitology / Q000502:physiology; D009036:Moths / Q000469:parasitology / Q000502:physiology; D029595:Orchidaceae / Q000502:physiology*; D018515:Plant Leaves / Q000378:metabolism / Q000469:parasitology; D054817:Pollination / Q000502:physiology*; D012903:Smell / Q000502:physiology; D014796:Visual Perception / Q000502:physiology; D014863:Wasps / Q000502:physiology*