DoesTraunsteinera globosa(the globe orchid) dupe its pollinators through generalized food deception or mimicry?

Abstract

Non-rewarding orchids rely on various ruses to attract their pollinators. One of the most common is for them to resemble flowers sought by insects as food sources. This can range from generalized food deception to the mimicry of specific sympatric food plants. We investigated the basis of pollinator deception in the European food-deceptive orchid Traunsteinera globosa, which has unusually compact flowerheads resembling those of sympatric rewarding species of Knautia and Scabiosa (Dipsacaceae), and Valeriana (Caprifoliaceae). Visual signals of T. globosa are similar in both fly and bee vision models to those of the sympatric food plants used in the choice experiments, but scent signals are divergent. Field experiments conducted in Austria and the Czech Republic showed that both naive and experienced (with respect to visitation of T. globosa) insect species approached the orchids at the same rate as food plants, but direct contact with orchid flowers was taxon specific. Flies were most easily duped into probing the orchid, and, in doing so, frequently received and deposited pollinaria, whereas most bees and butterflies avoided landing on orchid flowers. We conclude that T. globosa is a mimic of a guild of fly-pollinated plants, but the ecological dependence of the orchid on its models remains to be fully tested. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2016, 180, 269–294.